NEWS NEWSGGGGGlobal Elobal Elobal Elobal Elobal Energy and nergy and nergy and nergy and nergy and WWWWWater Cater Cater Cater Cater Cyyyyycle Ecle Ecle Ecle Ecle Experimentxperimentxperimentxperimentxperiment

TRMM passes over Cyclone Nargis (left figure) as it moves along the southern coastal region of Burma on 3 May 2008. Instantaneousrainfall rates from the TRMM Microwave Imager (outer swath) and the Precipitation Radar (inner swath) are superimposed on thecloud imagery from the Visible Infrared Scanner. Total accumulated precipitation (right figure) for the period 27 April to 4 May 2008from Nargis and precursor rain systems. Rainfall totals were derived from the TRMM multi-satellite 3-hourly precipitation product(images produced by Hal Pierce, National Aeronautics and Space Administration/Goddard Space Flight Center). See article by S. Braunon page 6.

Characterizing Rainfall RegimesUsing TRMM Data

TRMM Tracks Cyclone Nargis Approach to Burma

ContentsCommentary: A Year of Change

Recent News of Interest

GCSS Stratocumulus LES IntercomparisonsTargeting Climate Model Uncertainties

10+ Years of TRMM Precipitation Data

Retrieved Latent Heating from TRMM

Observing Rainfall Regimes Using TRMM PR and LIS Data

Trends or Artifacts? Temporal Changes in Cloud and Radiation Data from ISCCP, SRB and CERES

ISCCP Celebrates 25th Anniversary

GPCP 27-Yr Record Shows Regional/Global Trends and Correlation with Temperature

Meeting/Workshop Reports:

-18th Meeting of the GEWEX Radiation Panel 14-Mountain Hydroclimate Workshop 17

-2nd Meeting of the Intl Soil Moisture WG 19

GEWEX/WCRP Meetings Calendar 19

Tropical Rainfall Measuring Mission (TRMM) Data areImproving Our Understanding of the Global Energy and Water Cycle

May 2008Vol. 18, No. 2

12

11

6

9

3

2

8

Classified dominant rain systems using TRMM Precipitation Radar statistics in100-km scale boxes along the orbit and rainfall per flash values for 3 months.See article by Y. N. Takayabu on page 9.

13

3

May 20082

Commentary

A Year of Change:The Future of WCRP AND GEWEX

Peter J. van OevelenDirector, International GEWEX Project Office

This coming year should prove to be exciting,with many changes happening within the WorldClimate Research Programme (WCRP) and its coreprojects. It should also be an interesting chal-lenge for our research community to capitalize onthe increased media attention to climate changeand the widespread acceptance of the importanceof these and related issues. Mitigation and adap-tation are important key words in the governmentalresponse to climate change and we need to ensurethat scientific research will continue to play animportant role. An understanding of the globalprocesses and their regional effects is crucial formitigation and adaptation to be effective. GEWEXas a part of WCRP is at the core of these issuesand needs to strengthen its role more now thanever. I look forward to bringing these matters tothe forefront of attention.

It is with great pleasure that I welcome the newDirector of WCRP, Dr. Ghassem Asrar. We at theInternational GEWEX Project Office (IGPO) lookforward to working with Dr. Asrar in reshapingthe future of WCRP and its core projects whileensuring that the research they represent is bothmaintained and strengthened. One of Dr. Asrar’sfirst activities as Director was to attend the 29thWCRP Joint Scientific Committee (JSC) Meetingin Arcachon, France, held 31 March – 5 April.This meeting had a positive and cooperative spiritwhile addressing difficult issues, including the futureof WCRP as a whole, and the role and place ofthe WCRP Strategic Framework. This issue willno doubt stir up controversies on where and howto prioritize, but I am confident that this willprovide an excellent opportunity for GEWEX tocontinue its support and focus to activities in thelong term.

The JSC appointed a new chair, Dr. Antonio Busalacchiand I look forward to working with him. I will alsotake this opportunity to thank Dr. John Church forhis leadership as the chair during the last few years.The JSC was very supportive of activities relatedto monsoons but at the same time asked for strongercoordination among all involved parties; many ofthese issues no doubt will be brought to the tableat the next Pan-WCRP Monsoon meeting (to beheld 20–25 October of this year in Beijing, China).Similarly, the Extremes cross-cut is to be expandedand a Task Force on Climate Extremes is to be

formed with participation from the wider commu-nity. The JSC also approved the restructuring ofthe Working Group on Numerical Experimenta-tion (WGNE), which will include as members theGEWEX Modelling and Prediction Panel (GMPP)Working Group Chairs (the Global Land Atmo-sphere System Study, the GEWEX AtmosphericBoundary Layer Study, and the GEWEX CloudSystem Study) and the chair of GMPP, who willalso become an ex officio co-chair of WGNE. Thisrestructuring is aimed at endorsing, strengthen-ing, and expanding parameterization efforts in therespective communities.

The reprocessing of currently available global dataproducts with the purpose of making them moresuitable for climate and trend analysis is highlywelcomed and commended by the JSC, as evi-denced by the article written by Dr. EhrhardRaschke (et al.) on page 11 of this issue, high-lighting one of the difficulties in reprocessing theInternational Satellite Cloud Climatology Project(ISCCP) and related products. These data sets,originally intended for process studies on shortertime scales, will become even more valuable whentheir long-term consistency has been addressed.

The IGPO with the help of the wider communityis asked by the JSC to provide a legacy documentthat will assess and identify those activities whichneed to be further emphasized and those whichcan be downplayed in the intermediate term. Thiswill no doubt pose a challenge for all of us, sincemaking such choices will have both positive andnegative impacts. With WCRP's core projects nearingtheir sunset dates, some reorientation is unavoid-able and even necessary. I hope that we at theIGPO can continue to count on all of you assupporters of GEWEX research activities.

24–28 August 2009Melbourne, Australia

For updates, see www.gewex.org

Water in a Changing Climate: Progress inLand-Atmosphere Interactions and

Energy/Water Cycle Research

6th International Scientific Conferenceon the Global Energy and Water Cycle

and

2nd iLEAPS Science Conference

3May 2008

LANDSAT Imagery for Everyone

The U.S. Geological Survey (USGS) Landsat 35-yearrecord of the Earth’s surface will soon be available tousers at no charge. Under a transition toward a Na-tional Land Imaging Program sponsored by the Secretaryof the Interior, the USGS is pursuing an aggressiveschedule to provide users with electronic access to anyLandsat scene held in the USGS-managed nationalarchive of global scenes dating back to Landsat 1,launched in 1972. By February 2009, any Landsatarchive scene selected by a user will be automaticallyprocessed, at no charge, to a standard product recipeand staged for electronic retrieval. In addition, newlyacquired scenes meeting a cloud cover threshold of 20percent or below will be processed to the standardrecipe and placed online for at least 3 months, afterwhich they will remain available for selection from thearchive. For details see http://landsat.usgs.gov.

Pierre Morel Honored atEuropean Geophysical Union Meeting

GEWEX Welcomes New Director of WCRPJoint Planning Staff

Dr. Ghassem R. Asrar served asthe Deputy Administrator forNatural Resources and Agricul-tural Systems with the AgriculturalResearch Service of the U.S. De-partment of Agriculture from2006–2008. He was appointedto this position after 20 yearsof service with the U.S. NationalAeronautics and Space Admin-istration (NASA), where he served

as Chief Scientist for the Earth Observing System inthe Office of Earth Science at NASA Headquartersprior to being named as the Associate Administratorfor Earth Science in 1998. For more informationabout Dr. Asrar, see http://wcrp.wmo.int/documents/WCRPnews_20080221_Asrar.pdf.

Pierre Morel was awarded the EGU Alfred WegenerMedal for his outstanding contributions to geophysicalfluid dynamics and his leadership in the developmentof climate research and the applications of space obser-vation to meteorology and Earth system science.Throughout his 40-year career, Dr. Morel was one ofthe most active scientists initiating and developingtools and international programs for meteorological andclimatic research. From 1982 to 1994, as Director ofthe World Climate Research Programme, he steered abroad interdisciplinary research program in global cli-mate and Earth system science, involving the participationof atmospheric, oceanic, hydrological, and polar scien-tists worldwide.

Marine boundary-layer clouds exert a substantial short-wave radiative forcing on the global heat budget. Dueto problems in representing these clouds in generalcirculation models, they contribute a leading-orderuncertainty in cloud feedbacks in global climate mod-els (Bony and Dufresne, 2005).

The GEWEX Cloud System Study (GCSS) BoundaryLayer Cloud Working Group (BLCWG) has conducteda number of workshops devoted to idealized case stud-ies of low-lying clouds simulated with a range of models.The BLCWG intercomparison of large-eddy simula-tions (LES) focused on the first research flight of theDynamics and Chemistry of Marine Stratocumulus PhaseII (DYCOMS-II) field project in which very dry airoverlays a stratocumulus-topped marine boundary layerwith no measurable precipitation below the cloud base(Stevens et al., 2005a). Models that reduced subgrid-scale mixing at the cloud top were found best able tomaintain sufficient radiative cooling while concurrentlylimiting entrainment at the cloud top, resulting in awell-mixed boundary layer topped by an optically thickcloud layer. Cloud-water sedimentation and drizzle wereignored in those simulations, as is traditional in stud-ies of non-precipitating clouds.

While the importance of drizzle on the stratocumu-lus-topped boundary layer has been long acknowledged,only recently has the significance of cloud-watersedimentation been recognized in large-eddy simula-tions of stratocumulus (Ackerman et al., 2004;Bretherton et al., 2007). The BLCWG workshopfocused on the roles of cloud-water sedimentationand drizzle in a final ensemble of eleven LES mod-els, two of which used bin microphysics while therest used parameterized cloud microphysics. Thesimulation specifications were based on an idealiza-tion of the second research flight of DYCOMS-II,which sampled a bimodal cloud population withpockets of heavily drizzling open cells among a deckof closed-cell stratocumulus that was drizzling lightly(vanZanten and Stevens, 2005; Stevens et al., 2005b;Petters et al., 2006). Six-hour simulations were runwith and without drizzle, each with and withoutcloud-water sedimentation. Highlights of the resultsare presented here (a paper describing the resultsand implications has been provisionally accepted forpublication in Monthly Weather Review and is avail-able upon request from the author). The BLCWGhas also compared single-column models using thesame specifications developed for the LES intercomparison,as described by Wyant et al. (2007).

GCSS Stratocumulus Large-EddySimulation Intercomparisons Targeting

Climate Model Uncertainties

A. S. AckermanNASA Goddard Institute for Space StudiesNew York, NY, USA

Recent News of Interest

May 20084

leads to an increase in the third moment of w near thecloud base for all the simulations with drizzle; thusthe apparent disagreement between the measured andsimulated third moment of w can be attributed tothis process. Unfortunately the strength of this processwas exaggerated by roughly a factor of two in themodels that parameterize cloud microphysics (the speci-fied breadth of the cloud droplet size distribution wasbroader than measured, in retrospect), thus amplifyingits impact in the majority of simulations.

Sedimentation of cloud water was found to consis-tently result in decreased entrainment and increasedLWP, as found in other recent studies that have con-sidered the role of this process; however, there aresome differences with previous findings. For instance,Bretherton et al. (2007) considered the conditionsfrom the first research flight of DYCOMS-II and foundthat convective intensity (as measured by the varianceof w) increased throughout the bulk of the boundarylayer in response to cloud-water sedimentation reduc-ing entrainment. In this intercomparison, whichconsidered a much thicker cloud layer with less thanhalf the droplet concentration—factors that togetherenhance the parameterized cloud-water sedimenta-tion flux by up to a factor of five, cloud-watersedimentation was instead found to reduce convectiveintensity in most of the models. A sensitivity test withone of the models, in which drizzle is omitted andcloud-water sedimentation is parameterized, shows thatthis reduction of convective intensity nearly vanisheswhen the strength of cloud-water sedimentation ishalved. The stronger cloud-water sedimentation re-sults in a marked increase in the volume of unsaturatedair within the cloud layer, most pronounced near thecloud base. Thus, the evidence suggests that strongcloud-top sedimentation flux divergence of cloud water

not only reduces the efficiency of en-trainment—as found by Bretherton etal. (2007)—but also can result in dry,buoyant, and energetically unfavorabledowndrafts above the mean cloud base,as found by Stevens et al. (1998) insimulations of heavily drizzling stratocu-mulus.

The air overlying the boundary layer is slightly coolerand moister in this case compared to that in theprevious intercomparison (Stevens et al., 2005b), whichevidently allowed the model ensemble to do a muchbetter job of reproducing the observed entrainmentrate and liquid water path (LWP). For example, LWPvaried by less than a factor of two among the models,whereas LWP varied by more than an order of magni-tude among the models in the previous case. Thisimprovement in model agreement does not requirecloud-water sedimentation or drizzle (which were notconsidered in the previous intercomparison), as theensemble ranges of LWP are comparable both withand without those processes.

Time series characterizing the ensemble of simulationswith cloud-water sedimentation and drizzle are com-pared with the observations found in the figure below.After a transient spin-up of boundary-layer convection,the ensemble settles into a quasi-steady state in whichthe mean LWP reproduces the observed mean LWPremarkably well, while the mean entrainment rate is atthe lower end of the observations and the ensemble-average maximum vertical wind variance is roughly halfof that measured. On average, precipitation at thesurface and at the cloud base is smaller, and the rateof evaporation greater than measured. Comparison ofthe simulated and measured profiles provides furtherevidence that the simulated boundary layers are not aswell mixed as in the observations.

An indicator of the structure of the turbulent mix-ing—the mean third moment of w, the verticalwind—was observed to be negative near the cloudbase, indicating downdrafts stronger than updrafts. Incontrast, the skewness of w was positive near the cloudbase in the simulations. Cloud-water sedimentation

Evolution of domain average liquid water path(LWP), entrainment rate, maximum variance ofvertical wind, and surface precipitation for simu-lations that include cloud-water sedimentationand drizzle. The ensemble range, middle twoquartiles, and mean are denoted by light anddark shading and solid lines, respectively. En-semble mean from simulations that include drizzlebut not cloud-water sedimentation are denotedby dashed lines. Approximate ranges of mea-surement averages are denoted by dotted lines.

5May 2008

Turning from the effects of cloud-water sedimentationto those of drizzle (as models with bin microphysicsmake no distinction between cloud droplets and drizzledrops, a radius cutoff of 25 μm was used in theanalysis), LWP was found to decrease in response todrizzle in all but one of the models, despite a veryslight reduction in entrainment. Thus, while the ef-fects of cloud-water sedimentation and drizzle conspirewith respect to entrainment, their effects on LWP areopposed for all but one of the models, as seen in thefigure above. Taken together, the effect of cloud-watersedimentation on LWP dominates in all but two cases.That is, the inclusion of both processes results in a netLWP increase in nearly all the models. However, drizzleis not that strong in the simulations, and cloud-watersedimentation is exaggerated relative to the observa-tions in the models that parameterized it.

The changes in LWP and the vertical gradient oftotal water mixing ratio (i.e., vapor plus condensate)are strongly correlated in response to cloud-watersedimentation or drizzle, as seen above. The trend isalso strong when considering the effect of both pro-cesses combined. Drizzle is thus seen to increaseboundary-layer stratification in all but one of themodels, while the effect of cloud-water sedimenta-tion on stratification is more varied within theensemble, with stratification decreasing in nearly asmany models as those in which it increases.

In summary, the results here reinforce recent find-ings regarding the importance of cloud-watersedimentation to boundary-layer entrainment (andthereby cloud liquid water path), in this case reduc-ing the entrainment rate by approximately 25 percentor more (with or without drizzle included). It wasalso found that differences in model dynamics dominatethe spread in entrainment rates, which is of thesame order as the changes in entrainment rates in-duced by cloud-water sedimentation. Models thatentrain rapidly with microphysics omitted tended toentrain rapidly with microphysics included.

Change of LWP versus change of dif-ference in total water mixing ratio be-tween the sub-cloud and cloud layersof (äq

t) associated with cloud-water

sedimentation (left) and drizzle (right),averaged over last 4 hours of simula-tions. Drizzle is included in simula-tions on the left, and cloud-watersedimentation is included in simula-tions on the right.

AcknowledgementsAcknowledgementsAcknowledgementsAcknowledgementsAcknowledgements

Thanks to M. C. vanZanten (KNMI), B. Stevens (UCLA),V. Savic-Jovcic (UCLA), C. S. Bretherton (U. Washington), A. Chlond(MPI), J.-C. Golaz (NOAA-GFDL), H. Jiang (NOAA-ESRL),M. Khairoutdinov (Stony Brook U.), S. K. Krueger (U. Utah),D. C. Lewellen (West Virginia U.), A. Lock (MetO), C.-H. Moeng(NCAR), K. Nakamura (JAMSTEC), M. D. Petters (Colorado StateU.), J. R. Snider (U. Wyoming), S. Weinbrecht (U. Reading), andM. Zulauf (U. Utah) for participating in the intercomparison.

ReferencesReferencesReferencesReferencesReferences

Ackerman, A. S., M. P. Kirkpatrick, D. E. Stevens, and O. B.Toon, 2004. The impact of humidity above stratiform clouds onindirect aerosol climate forcing. Nature, 432, 1014–1017.

Bony, S., and J. Dufresne, 2005. Marine boundary layer clouds atthe heart of tropical cloud feedback uncertainties in climate mod-els. Geophys. Res. Lett., 32(L20806).

Bretherton, C., P. Blossey, and J. Uchida, 2007. Cloud dropletsedimentation, entrainment efficiency, and subtropical stratocumu-lus albedo. Geophys. Res. Lett., 34(L03813).

Petters, M. D., J. R. Snider, B. Stevens, G. Vali, I. Faloona, andL. Russell, 2006. Accumulation mode aerosol, pockets of opencells, and particle nucleation in the remote subtropical Pacificmarine boundary layer. J. Geophys. Res., 111(D02206).

Stevens, B., W. R. Cotton, G. Feingold, and C.-H. Moeng, 1998.Large-eddy simulations of strongly precipitating, shallow, stra-tocumulus-topped boundary layers. J. Atmos. Sci., 55, 3616–3638.

Stevens, B. et al., 2005a. Evaluation of large-eddy simulations viaobservations of nocturnal marine stratocumulus. Mon. Wea. Rev.,133, 1443–1462.

Stevens, B., G. Vali, K. Comstock, M. C. vanZanten, P. H. Austin,C. S. Bretherton, and D. Lenschow, 2005b. Pockets of open cells(POCs) and drizzle in marine stratocumulus. Bull. Amer. Meteor.Soc., 86, 51–57.

Wyant, M. et al., 2007. A single-column model intercomparison ofa heavily drizzling stratocumulus-topped boundary layer. J. Geophys.Res., 112(D24204).

vanZanten, M. C., and B. Stevens, 2005. Observations of thestructure of heavily precipitating marine stratocumulus. J. Atmos.Sci., 62, 4327–4342.

May 20086

and tropical cyclones; and new insights into the im-pacts of humans on rainfall. The availability of real-timeTRMM data has led to significant applications andthe operational use of the data, primarily in monitor-ing tropical cyclones, in hydrological applications, andin the assimilation of precipitation information intonumerical forecast models. As the key satellite overthe past decade dedicated to precipitation observa-tions, TRMM has contributed significantly to thegoals of GEWEX and the World Climate ResearchProgramme (WCRP). For example, TRMM data arebeing compared to current tropical estimates underthe GEWEX Global Precipitation Climatology Project(GPCP) and will be extensively used in new versionsof GPCP products being planned.

The recent devastation in Burma by Tropical CycloneNargis highlights the need for high-quality space-basedobservations of cyclone track, structure, and rainfall.Nargis made landfall in Burma with 115 knot windsand produced rainfall upwards of 200 mm. The situ-ation was exacerbated by the fact that, in the daysprior to landfall, heavy precipitation embedded in thesoutherly flow ahead of Nargis dropped nearly 300mm of precipitation in the region. The value of theTRMM data is seen at the top of page 1, illustratingthe information on storm structure from the orbit dataand estimates of total rainfall from the TRMM multi-satellite precipitation product (Huffman et al., 2007).

TRMM data (primarily TMI) are used by both theNational Oceanic and Atmospheric Administration's Na-tional Hurricane Center and the Department of DefenseJoint Typhoon Warning Center in the United States,as well as tropical cyclone centers in Japan, India,Australia, and other countries for detecting the loca-tion and intensity of tropical cyclones. In 2004, morethan 600 tropical cyclone fixes were made by theseagencies using TRMM data. Because of TRMM’s finerspatial resolution as compared to the Special SensorMicrowave Imager (SSM/I), these fixes are usually con-sidered among the most accurate of satellite-basedlocations. In addition, TRMM’s orbit in the tropicsprovides data at different times than the sun-synchro-nous microwave instruments, with its best sampling inthe cyclone-important 10–37 degree latitude bands.TRMM data are also used (often in time historieswith other satellite data) to detect changes in convec-tion, eyewall formation, and other features related tointensity change and are frequently mentioned in warningcenter discussions.

TRMM has provided an invaluable data resource fortropical cyclone research as its TMI and PR data havebeen used to establish for the first time key character-istics of the distribution and variation of rainfall intropical cyclones as a function of intensity, basin, stageof development, and environmental conditions (e.g.,shear) (Lonfat et al., 2004; Chen et al., 2006). TRMMPR and TMI data have been used to derive vertical

10+ Years of TRMM Precipitation Data

Launched in 1997, the Tropical Rainfall MeasuringMission (TRMM), a joint U.S. National Aeronauticsand Space Administration (NASA) and Japan Aero-space Exploration Agency (JAXA) program, has providedunique information on precipitation structure and dis-tribution for more than 10 years. The first-time use ofboth active and passive microwave instruments and itsprecessing, low inclination orbit (35°) have made TRMMthe world’s foremost satellite for the study of precipita-tion and associated storms and climate processes in thetropics. TRMM has met and exceeded its original goalof advancing our understanding of the distribution oftropical rainfall and its relation to the global water andenergy cycles. It has evolved from an experimentalmission focusing on tropical rainfall climatology intothe primary satellite used for analyzing precipitationcharacteristics on time scales from 3-hourly tointerannually and beyond.The primary TRMM instruments are the PrecipitationRadar (PR), the first and only rain radar in space, andthe TRMM Microwave Imager (TMI), a multi-chan-nel passive microwave radiometer that complementsthe PR by providing total hydrometeor (liquid andice) content within precipitating systems. The VisibleInfrared Scanner (VIRS) provides the cloud context ofthe precipitation structures and is used as part of atransfer strategy to connect microwave precipitationinformation to infrared-based precipitation estimatesfrom geosynchronous satellites. These three instruments,which form the original TRMM rain package are usedsingly and jointly to understand precipitation pro-cesses, structure, and climatology. In addition, theLightning Imaging Sensor (LIS), an Earth ObservingSystem (EOS)-funded instrument, complements therain sensors, improving understanding of convectivedynamics and providing a climatology of global light-ning flash rates. The TRMM orbit altitude originallywas 350 km with an inclination of 35° for coverage ofthe tropics and the southern portions of both Japanand the United States. The precessing orbit also passesthrough all the hours of the day, thereby giving aunique data set for observing the diurnal cycle ofrainfall. In order to conserve fuel and extend the mis-sion of TRMM, the orbit was boosted to 402.5 km inAugust 2001 and TRMM has operated at that alti-tude ever since.Significant scientific accomplishments have been madefrom TRMM data resulting in more than 800 refereedjournal articles. These accomplishments include reduc-ing the uncertainty of mean tropical oceanic rainfall;documentation of regional, diurnal, and interannualvariations in precipitation characteristics; the first esti-mated profiles of latent heating from satellite data (seearticle on page 8); improved climate simulations; in-creased knowledge of characteristics of convective systems

Scott A. BraunNASA/Goddard Space Flight Center

7May 2008

profiles of precipitation ice and liquid water contentin tropical cyclones (Jiang and Zipser, 2006). Theability of TRMM to see within cloud systems enablesus to detect the eye of topical cyclones much moreconsistently than with infrared sensors (89 percentvs. 37 percent) (Kodama and Yamada, 2005) whileobservations of deep convective towers in the eyewallhave been linked to the subsequent deepening ofstorms (Kelley et al., 2004). TRMM data have alsobeen used to validate mesoscale model simulationsof hurricanes (Braun, 2006) and have been demon-strated to have made positive impacts through dataassimilation on simulations (Atlas et al., 2005; Maet al., 2006) and forecasts (Benedetti et al., 2005)of tropical cyclones.

TRMM instantaneous rain estimates have been usedto calibrate or adjust rain estimates from other satel-lites to provide analyses at higher time resolution thanavailable from one satellite (Adler et al., 2000). TRMMcurrently provides a 3-hour multisatellite precipitationanalysis product (Huffman et al., 2007) that is themost frequently downloaded product from the TRMMdata archive (see the TRMM 3B42 product at http://disc.sci.gsfc.nasa.gov/data/datapool/TRMM). This productis used to validate models (Bauer and Del Genio,2005), estimate rainfall associated with tropical cy-clones, and identify regions susceptible to floods andlandslides (Hong et al., 2006).

After 10 years of operation, all TRMM instrumentsare performing well and the spacecraft has sufficientfuel to maintain operations until at least late 2013and potentially through 2014. Continuation of TRMMdata until 2014 will allow the community to betterlink the TRMM data set to that of the Global Precipi-tation Measurement (GPM) mission scheduled to belaunched in 2013. TRMM and GPM together willproduce a 20-year plus high-quality rainfall recordthat will allow scientists to determine the time andspace varying characteristics of tropical rainfall, convec-tive systems, and storms and how these characteristicsare related to variations in the global water and energycycles. Such work has long been a primary goal ofTRMM and is at the heart of NASA’s Earth Sciencestrategy. It will help to answer key science questionsfor both the water and energy cycle and weather focusareas, including “How are global precipitation, evapo-ration, and the water cycle changing?” and “How canweather forecast duration and reliability be improved?”The presence of a long, accurate record of quasi-globalprecipitation characteristics will greatly advance pre-cipitation science and result in: (1) an improvedclimatology of precipitation characteristics, especiallyextremes; (2) improved diagnosis and closure of global(and regional) water cycles; (3) diagnosis and testingof inter-decadal and trend-related processes in the watercycle; (4) better assessment of the impact of humanson rainfall characteristics and processes (e.g., cities,deforestation, and aerosols); (5) robust determination

of convective system, tropical cyclone, and lightningcharacteristics; (6) advances in hydrological applicationsover land (basin-scale assessments, water management);(7) improved modelling of the global water/energycycles for weather/climate predictions; and (8) im-proved monitoring and forecasting of tropical cyclones,floods, and other hazardous weather.

Key web sites related to TRMM and its observationsof tropical cyclones include: http://www.trmm.gsfc.nasa.gov(U.S. TRMM), http://www.eorc.jaxa.jp/TRMM/index_e.htm(Japanese TRMM), and http://www.nrlmry.navy.mil/tc_pages/tc_home.html (Naval Research Laboratory).

ReferencesReferencesReferencesReferencesReferences

Adler, R. F., G. J. Huffman, D. T. Bolvin, S. Curtis, and E. J. Nelkin,2000. Tropical rainfall distributions determined using TRMM com-bined with other satellite and raingauge information. J. Appl. Meteor.,39, 2007–2023.

Atlas, R., A. Y. Hou, and O. Reale, 2005. Application of SeaWindsscatterometer and TMI-SSM/I rain rates to hurricane analysis andforecasting. J. Photo. And Remote Sensing, 59, 233–243.

Bauer, M., and A. D. Del Genio, 2005. Composite analysis of wintercyclones in a GCM: Influence on climatological humidity. J. Climate,19, 1652–1672.

Benedetti, A., P. Lopez, P. Bauer, and E. Moreau, 2005. Experimentaluse of TRMM precipitation radar observations in 1D+4D-Var assimi-lation. Quart. J. Roy. Met. Soc., 131, 2473–2495.

Braun, S. A., 2006. High-resolution simulation of Hurricane Bonnie(1998). Part II: Water budget. J. Atmos. Sci., 63, 43–64.

Chen, S. Y. S., J. A. Knaff, and F. D. Marks, 2006. Effects of verticalwind shear and storm motion on tropical cyclone rainfall asymmetriesdeduced from TRMM. Mon. Wea. Rev., 134, 3190–3208.

Hong, Y., R. Adler, and G. Huffman, 2006. Evaluation of the poten-tial of NASA multi-satellite precipitation analysis in global landslidehazard assessment. Geophys. Res. Lett., 33(22): Art. No. L22402.

Huffman, G. J., R. F. Adler, D. T. Bolvin, G. Gu, E. J. Nelkin, K.P. Bowman, E. F. Stocker, and D. B. Wolff, 2007. The TRMMMulti-satellite Precipitation Analysis: Quasi-global, multi-year, com-bined-sensor precipitation estimates at fine scale. J. Hydrometeor., 8,38–55.

Jiang, H. Y., and E. J. Zipser, 2006. Retrieval of hydrometeor profilesin tropical cyclones and convection from combined radar and radiom-eter observations. J. Appl. Met. Clim., 45, 1096–1115.

Kelley, O., J. Stout, and J. Halverson, 2004. Tall precipitation cellsin tropical cyclone eyewalls are associated with tropical cyclone inten-sification. Geophys. Res. Lett., 31, L24112.

Kodama, Y. M., and T. Yamada, 2005. Detectability and configura-tion of tropical cyclone eyes over the western North Pacific in TRMMPR and IR observations. Mon. Wea. Rev., 133, 2213–2226.

Lonfat, M., F. D. Marks, Jr., and S. S. Chen, 2004. Precipitationdistribution in tropical cyclones using the TRMM imager: A globalperspective. Mon. Wea. Rev., 132, 1645-1660.

Magagi, R. and Barros, A.P., 2004. Latent Heating of Rainfall Duringthe Onset of the Indian Monsoon using TRMM-PR and RadiosondeData. J. Appl. Meteor., 43, 328–349.

Ma, L. M., Z. H. Qin, Y. H. Duan, X. D. Liang, and D. L. Wang,2006. Impacts of TRMM SRR assimilation on the numerical predic-tion of tropical cyclone. Acta Ocean. Sinica, 25, 14–26.

May 20088

LH requirements and applications issues, (4) deter-mine the uncertainties of LH products, and (5) identifyissues pertaining to use of TRMM and other satelliteLH data for global-scale modelling and tropical con-vection studies. A recommendation from these workshopswas to conduct a TRMM LH intercomparison andvalidation project.

Seven separate data sets and four field experiment casesare considered for this intercomparison project (seeTable 2 above): the South China Sea Monsoon Experi-ment (SCSMEX), the Large Scale Biosphere-AtmosphereExperiment in Amazonia (LBA), the Kwajalein Experi-ment (KWAJEX), and the U.S. Department ofEnergy-Atmospheric Radiation Measurement (ARM)Southern Great Plains-Cloud and Radiation Test Bed;two tropical cyclone cases: Atlantic Hurricane Bonnieand Pacific Typhoon Jelawat; and one large-scale re-gional case: a tropical ocean domain.

The intercomparison results are illustrated here usingthe SCSMEX south enhanced sounding arrays (SESA)case (see figure at the top of page 20). The sounding-estimated Q1 (two different averaging areas) andsatellite-derived QR are also shown for comparison.The CSH (Q1) and SLH (both Q1–QR and LH) algo-rithms agree with the sounding-estimated Q1 in termsof amplitude of peak heating and having a broadheating peak. However, their retrieved peak heatinglevel is slightly higher than that estimated from thesoundings. GPROF-retrieved heating (Q1 and Q1–QR)also agrees with the sounding estimates, but has smalleramplitude (especially in the lower troposphere) com-pared to the other algorithms. The LH-retrieved heatingagrees with that estimated from sounding data in terms

Retrieved Latent Heating From TRMM

Wei-Kuo Tao1, Robert Houze, Jr.2, and Eric A. Smith1

1 Laboratory for Atmospheres, NASA/Goddard SpaceFlight Center, Greenbelt, MD, USA; 2 University of Wash-ington, Department of Atmospheric Sciences, Seattle,WA, USA

Latent heating (LH) is the heat released or absorbedby the atmosphere as a result of phase changes inwater associated with condensation or evaporation ofcloud droplets and raindrops, freezing of raindrops,melting of snow and graupel/hail, or the depositionand sublimation of ice particles. The Tropical RainfallMeasuring Mission (TRMM) Precipitation Radar (PR)and Microwave Imager (TMI) provide measurementsof rainfall as well as an estimate of the four-dimen-sional structure of latent (diabatic) heating over theglobal tropics (Simpson et al., 1988, 1996). Becausethe PR and TMI cannot directly measure LH profiles,they have to be determined indirectly from the appli-cation of physically based models to TRMM precipitationmeasurements. The general approach is to apply mod-els ranging in complexity from simple profile shapes tocloud-resolving models (CRMs) to the PR and/or TMIdata (Tao et al., 2006).

Five TRMM LH algorithms have been developed, com-pared, validated, and applied during the past decadeand are listed below in Table 1. The CSH, GPROF,and SLH algorithms require the full complement ofcloud model data generated by a CRM. Since May2001, five TRMM LH workshops (Tao et al., 2007)have been held to (1) review LH algorithm designsand planned improvements, (2) assess validation schemesand results with diagnostic-type analyses, (3) identify

Table 1. Key characteristics of five different heating algorithmsin terms of data requirement and retrieved products. Note that therelationship between Q

1 (apparent heating source, which can be

diagnostically determined from an intensive sounding network),LH, Q

1–Q

R and Q

R is: Q

1–Q

R=LH+Eddy transport by clouds. The

vertically integrated eddy transport by clouds is zero (no expliciteffect on surface rainfall). Complete references can be obtainedfrom the authors.

Table 2. Satellite sampling and domain size of sounding networkfor intercomparison cases. The first four cases are validated withthe apparent heating (Q

1) derived from diagnostic budget calcu-

lations based on observations from special radiosonde or com-bined radiosonde-Doppler radar networks. The two tropical cyclones(Cases 5 and 6) allow for the algorithm-generated instantaneousLH profiles to be compared—but without validation information.In the final case, the intercomparisons focused on a hierarchy ofspace-time scale variations (including inter-annual variations)over large-scale regional domains involving tropical ocean envi-ronments.

Sampling Ratio(Satellite/diagnostic)

Area Size(km x km)

Date

Case 1a: SCSMEX

NESA53% 665 x 1100 18 May - 30 June 1998

Case 1b: SCSMEX

SESA48% 880 x 880 1 May - 30 June 1998

Case 2: LBA 19% 190 x 190 24 Jan - 28 Feb 1999

Case 3: KWAJEX 16% 175 x 175 24 July - 14 Sept 1999

Case 4a: ARM 2000 38% 400 x 400 1 March - 21March 2000

Case 4b: ARM 2002 39% 400 x 400 25 May - 15 June 2002

Case 5: Bonnie N.A. ~500 x 500 1806 UTC, 22 August 1998

Case 6: Jelawat N.A. ~500 x 500 1151 UTC, 2 August 2000

Case 7: Ocean N.A. 4,440 x 9,900 Jan 1998 - Dec 2000

TRMMData

Needed

HeatingProducts

KeyReferencesin AlgorithmDescription

AlgorithmDevelopers

CSH (Convective-

Stratiform Heating)

PR, MI,

PR-TMIQ

1, LH

Tao et al. (1993;

2000, 2001)

W.-K. Tao and

S. E. Lang

SLH (Spectral Latent

Heating)PR Q

1, Q

1-Q

R

Shige et al.

(2004)

S. Shige and Y. N.

Takayabu

GPROF

(Goddard ProfilingHeating)

PR-TMI Q1, Q1-QR

Olson et al.

(1999, 2006)

W. S. Olson and

C. D. Kummerow

HH (Hydrometeor

Heating)PR-TMI LH

Yang et al.

(1999, 2006)

E. A. Smith and

Y. Song

PRH (PrecipitationRadar Heating)

PR LHSatoh and Noda

(2001)S. Satoh and

A. Noda

9May 2008

Table 3. Key scientists using TRMM-derived LH products forspecific applications. MJO stands for Madden-Julian oscillation.

of altitude of maximum heating and having positiveheating in the upper troposphere (above 10 km). Itsretrieved heating is larger than the other algorithms.The PRH-retrieved heating profile has the lowestmaximum heating altitude. These preliminary resultsare quite encouraging despite sampling issues (see Table2), because each algorithm’s retrieved heating structurecaptured some of the major characteristics estimatedfrom the sounding network.

In the last decade, standard LH products from TRMMmeasurements have been developed for scientific re-search and applications (Table 3). Such products enablenew insights and investigations of the complexities ofconvective life cycles, the diabatic heating controls andfeedbacks of meso-synoptic circulations and their fore-casts, the relationship of patterns of tropical LH to theglobal circulation and climate, and of strategies forimproving cloud parameterizations in environmentalprediction models. The distributions of rainfall andinferred heating can be used to advance understandingof the global energy and water cycle. In addition, thisinformation can be used for global circulation andclimate models for validating and improving theirparameterizations.

ReferencesReferencesReferencesReferencesReferences

Tao, W.-K., E. A. Smith, R. F. Adler, et al., 2006. Retrieval oflatent heating from TRMM satellite measurements. Bull. Amer.Meteor. Soc., 87, 1555–1572.

Tao, W.-K., R. A. Houze, Jr., and E. A. Smith, 2007. The FourthTRMM Latent Heating Workshop. Bull. Amer. Meteorol. Soc., 88,1255–1259.

Simpson, J., R. F. Adler, and G. North, 1988. A proposed TropicalRainfall Measuring Mission (TRMM) satellite. Bull. Amer. Meteor.Soc., 69, 278–295.

Simpson, J., C. Kummerow, W.-K. Tao, and R. Adler, 1996. Onthe Tropical Rainfall Measuring Mission. Meteorol. Atmos. Phys., 60,19–36.

HeatingProducts Usedfor Applications

> Ten Applications - 5 papers

Drs. Krishnamurti,Rajendran (FSU, MRI)

CSH Global Model Assimilation

Dr. A. Del Genio (GISS) CSHLarge-Scale Modeling Validation

(Level of Max Heating)

Dr. A. Hou (GSFC) GPROF Global Model Assimilation

Dr. D. Waliser (JPL) CSH/GPROFComparison between Global Model

(ECMWF) and TRMM Derived for MJO

Dr. C. Zhang (U. Miami) CSH/SLHLH and Large-Scale Dynamic

(MJO and Shallow Meridional Circulation)

Dr. X. Zhang (U. Colorado) CSHRelationship between LH and

Mesosphere and Low ThermosphereSolar Tides

Dr. W. Lau (GSFC) CSH Evolution of MJO

Dr. R. Small (U. Hawaii) GPROF/CSHTropical Circulation Response to LH

Anomalies

Dr. P. Webster(Georgia Tech.)

GPROF/CSH Monsoon

Drs. J. Morita, Y. N.Takayabu (CCSR/U. Tokyo)

SLH LH Structures of MJO

Yukari N. TakayabuCenter for Climate System ResearchUniversity of Tokyo, Japan

Observing Rainfall RegimesUsing TRMM PR and LIS Data

Rainfall is often referred to in terms of “oceanic” and“continental” regimes of precipitation, the latter havingmore vigorous convection and lightning activity. Williamset al. (1992) introduced the concept of Rainyield perFlash (RPF), showing a large contrast between RPFvalues of monsoon active and break periods. Petersenand Rutledge (1998) showed that this difference isattributed to the rainfall characteristics being morecontinental for the monsoon active period and moreoceanic for the break period. This article describes howTropical Rainfall Measuring Mission (TRMM) Precipi-tation Radar (PR) and Lightning Imaging Sensor (LIS)data were used to characterize rainfall and classify thedominant rainfall systems using the value of RPF.

The upper panel in the figure at the top of page 10shows the 8-year averaged RPF distribution calculatedusing PR and LIS data, and the lower panel shows the8-year average PR-based rain rate (Takayabu, 2006).The reddish colors of RPF show more lightning andbluish colors show less lightning for an equal amountof rain. It is readily noticeable that while the rainamount distribution is relatively continuous betweenland and ocean, significant land-ocean contrast emergesin the RPF distribution. Smaller values are found overland than over ocean. Considering that the RPF is therain amount normalized with the lightning flash num-bers, it is an “intensive” variable which representscharacteristics of rain independent from the amount.RPF values show a clear contrast between the oceanicrainfall characteristics and the continental rainfall, withaverage values of 2.0x109kgfl–1 for the former and3.9x108kgfl–1 for the latter for the entire TRMM ob-servation region between 36N and 36S.

This figure also shows some interesting regional char-acteristics. RPFs over continental rainy regions such asthe Amazon and the Indian and southeast Asian mon-soon regions exhibit intermediate values (orange). Whenthe seasons are separated, the RPF values in monsoonregions are continental in the premonsoon season, whilein the wet season they are oceanic. The figure at thebottom of page 10 contrasts the RPF values over SouthAmerica in the premonsoon September-November sea-son with those in the wet March-May season. Whilethe RPF is as small as that of the annual-mean equa-torial Africa in the relatively dry September-Novemberseason, it is as oceanic as that of the coastal ocean inthe wet March-May season.

The region with intermediate RPF values (green) canbe defined as “transition zones,” where RPF is lessthan the threshold of 50x107kg fl–1 over the ocean.

May 200810

This transition zone is found mostly around the conti-nents. RPF correlates well with the rainfall amount fromvery high (<–20oC) rain top height (RTH) for continen-tal rainfall, but the correlation disappears for oceanic rain.The rainfall in the transition zone shows a good correla-tion with the high rain amount, even though it is oceanicrain. It is interesting to consider how rainfall in thetransition zone acquires continental characteristics.

These RPF values are used along with the statistics ofPR2a25 data in ~100 km mesoscale boxes (21x21PRpixels) along the orbit to classify the rainfall types interms of associated dynamical processes. Rainfall amount,rainfall area, and RTH statistics are used together withthe RPF to determine the dominant rain type in 2.5x2.5degree grid boxes for every 3 months (Takayabu et al.,in preparation). The figure at the bottom of page 1shows an example of rain type classification for Septem-ber-November and December–February 2001. Grids areassigned to different rain types over land (severe thun-derstorm, afternoon shower, shallow rain, extratropicalfrontal systems, organized rain, or high land rainfall),

RPF distributions over South America for 8-year average September–November season and March–May season.

and over the ocean (shallow rain, extratropical frontalsystems, organized rain, and transition zone). These re-sults are used in the Global Satellite Mapping of Precipitation(GSMaP), a project sponsored by the Japan AerospaceExploration Agency (JAXA) to produce high precisionand high resolution global precipitation maps using sat-ellite data. Statistics of rainfall based on such rain typeclassifications will also be used in the evaluation of pre-cipitation systems in climate models.

ReferencesReferencesReferencesReferencesReferences

Petersen, W. A., and S. A. Rutledge, 1998. On the relationshipbetween cloud-to-ground lightning and convective rainfall. J. Geophys.Res., 13(D12), 14025–14040.

Takayabu, Y. N., 2006. Rain-yield per flash calculated from TRMMPR and LIS data and its relationship to the contribution of tallconvective rain. Geophys. Res. Lett., 33, L18705, doi:10.1029/2006GL027531.

Williams, E. R., S. A. Rutledge, S. G. Geotis, N. Renno, E.Rasmussen, and T. Rickenbach, 1992. A radar and electrical studyof tropical “hot towers.” J. Atmos. Sci., 49, 1386–1395.

Global distributions of 8-year meanRainyield per Flash (RPF) calculated fromTropical Rainfall Measuring Mission(TRMM) Precipitation Radar (PR) and Light-ning Imaging Sensor (LIS) data (top panel)and total rain observed from TRMM PR(bottom panel). Units for the color scalesare 107 kg fl–1 (top) and mm hr–1 (bot-tom). RPF averages are obtained by di-viding the total precipitation amount bythe total flash number for the averagingperiod.

11May 2008

Trends or Artifacts? Temporal Changes inCloud and Radiation Data from

ISCCP, SRB, AND CERES

Since 1983, the International Satellite Cloud Climatol-ogy Project (ISCCP) (Rossow and Duenas, 2004) hasprocessed visible and infrared images from polar andgeostationary satellites to produce monthly 2.5 degreedata sets of global cloud cover and radiative properties.Global monthly cloud products at 280-km resolutionwith 72 variables and 3-hour intervals, derived frompolar orbiting and geostationary meteorological satellitesnow form an extensive 25-year global family of datasets. These resulting data sets and analysis products arebeing used to improve our understanding and model-ling of the role of clouds in climate, with the primaryfocus of studying cloud and radiation process on shortertime scales where the magnitude of variations is large, asopposed to small long-term variations of the climate.These data are also being used to support many othercloud studies, including the hydrological cycle. WhileISCCP was not originally designed as a “climate datarecord,” there has been increasing interest in that usedue to the growing length of data record. There are,however, a number of features that make the currentproducts less useful for that purpose. Investigating thesources of inconsistencies is a necessary precursor to acareful re-analysis of all these data products. Approvalhas been obtained to re-engineer the ISCCP processing

Time-series of deseasonalized zonal monthly averages of the skin temperature at the surface (left panel) and of the total amountof clouds (right panel) from the period of July 1983 to June 2004.

system to attempt to improve the quality enough toform a cloud Climate Data Record

Some recent papers have proposed interpretations ofbroad temporal changes—or “trends”—in the ISCCPcloud products and in the related radiation products ofISCCP, which include the GEWEX Surface RadiationBudget (SRB) Project (Stackhouse et al., 2004), andthe Clouds and the Earth’s Radiant Energy System(CERES) Experiment (Loeb et al., 2007). Some inter-pretations of these important data sets are controversialand demand a second look. For example, some correla-tions to changes in input ancillary data are found whenassessing time series of cloud climatology and radiationproducts. This suggests that some or all of the broadtemporal changes in these products may be artifactscaused by various input data.

Essential ancillary data to radiation products are clouds,surface properties of solar albedo and skin temperature,and atmospheric data on air temperature, trace gases,and aerosol. The figure below gives an example of howinconsistencies in input ancillary data might influencethe radiation products. The left panel shows that largerchanges for skin temperature occur in the subtropicaland tropical regions. Clearly noticeable is a coolingfollowing the Mt. Pinatubo eruption in 1991 by morethan 1 K, whereas the real cooling at ground level wasless than 0.5 K (Reynolds, 1993). After 1994 there isa significant decline of the skin temperature, whichends abruptly with a sharp increase by more than 3 Kin 2001. Similar structures are found in other ancillarydata, including atmospheric temperature, water vapor,and even surface reflectance (see http://ISCCP.giss.nasa.gov,and Zhang et al., 2006, 2007). These tropical tem-perature anomalies are an artifact related to changes in

Ehrhard Raschke1, Stefan Kinne2,William B. Rossow,3 and Yuan-Chong Zhang4

1University of Hamburg, Hamburg, Germany;2Max-Planck-Institute for Meteorology, Hamburg, Germany;3City College of New York, USA;4Columbia University, New York, USA

May 200812

the analysis algorithm used to produce the atmo-spheric temperature and humidity data used for ISCCPretrieval.

The ISCCP total cloud cover in the right panel, whichis between 50° northern and southern latitude, seemsto decrease almost continuously from 1988 to 2001.It has been proposed but not yet demonstrated that atleast some of this variation is an artifact; we are stillstudying this question. Both of these parameters areused to produce the ISCCP-FD and GEWEX SRBradiative flux products, so that artifacts in these andpossibly other inputs would cause artifacts in the ra-diation products that may be mistaken as trends.

The Pinatubo aerosols (1991) do not increase the totalcloud cover much but they do change the partitioningof cloud amount between low and high clouds. Thereare some other correlations that are not yet under-stood, such as why the higher skin temperature since2001 coincides with more high level clouds and fewerlow level clouds.

Inconsistencies in ancillary data are not just limited toISCCP: they also appear in climatologies such as SRBand CERES. CERES data are available only since theyear 2000. Thus, direct comparisons of applied ancil-lary data for these three climatologies are available fora only a few years. Comparisons for the ancillary dataof solar surface albedo and infrared surface emissionfluxes are given in the figure on the bottom of page20, displaying the differences in annual averages be-tween data sets of SRB and CERES climatologies withrespect to ISCCP data. The figure shows that SRBuses lower surface reflectances at extratropical latitudes,especially in areas where snow cover is expected. CERESsurfaces are slightly brighter than ISCCP over conti-nents, with the exception of Central Asia. The surfacesin the SRB and CERES algorithms are warmer over allthe oceans than the ISCCP surfaces during the years2000 and 2001, becoming colder in the following twoyears due to the sharp temperature rise discussed inthe figure on page 11. Only southern oceans and partsof the Northern Pacific and Northern Atlantic remainwarmer.

Such inconsistencies propagate into all radiation prod-ucts of the three GEWEX radiation projects. A carefulinspection of all ancillary data with respect to artifactsand spurious trends is required. Furthermore, it wouldbe desirable to set up an ancillary data set time seriesfor common use in such climatologies to allow re-searchers to focus their analyses on the more complexfactors influencing radiation products and at the sametime increase the potential to identify real trends.

This work is a contribution to the official assessmentof GEWEX water vapor, cloud, aerosol, and radiationproducts.

ReferencesReferencesReferencesReferencesReferences

Loeb, N. G., B. A. Wielicki, F. G. Rose, and D. R. Doelling, 2007.Variability in global top of atmosphere shortwave radiation between2000 and 2005. Geophys. Res. Lett., 34, L03704.

Reynolds, R. W., 1993. Impact of Mount Pinatubo aerosols on sat-ellite-derived sea surface temperatures. J. Climate, 6, 768–774.

Rossow, W. R., and E. Duenas, 2004. The International SatelliteCloud Climatology Project (ISCCP) website – An online resource forresearch. Bull. Am. Meteor. Soc., 85, 167–172.

Stackhouse, P. W., Jr., S. K. Gupta, S. J. Cox, J. V. Mikovitz, T.Zhang, and M. Chiacchio, 2004. 12-year surface radiation budgetdataset. GEWEX News, 14(4), 10–12.

Zhang, Y.-C., W. B. Rossow, and P. W. Stackhouse, 2006. Compari-son of different global information sources used in surface radiativeflux calculation: Radiative properties of the near-surface atmosphere.J. Geophys. Res., 111, D13106.

Zhang, Y.-C., W. B. Rossow, and P. W. Stackhouse, 2007. Compari-son of different global information sources used in surface radiativeflux calculation: Radiative properties of the surface. J. Geophys. Res.,112, D01102.

In July 2008, the International Satellite CloudClimatology Project (ISCCP), the first project of theWorld Climate Research Programme, will mark its 25th

Anniversary. The original concept for ISCCP was tocollect and distribute enough global satellite data tofacilitate research on the role of clouds in climate,specifically their effects on the radiation budget andtheir role in the atmospheric water cycle. These datawere to be sampled at sufficiently fine space-timeintervals to capture the mesoscale-to-global scale anddiurnal-to-interannual variations of cloud physicalproperties.

In addition to calibrating, navigating, quality checkingand distributing the satellite radiance data for thewhole research community to use, ISCCP conducteda comparison of the then-existing cloud algorithmsand participated in comparisons of radiative modelrepresentations of clouds—work that is on-going to-day. Based on these results, a new algorithm wasdesigned, borrowing ideas from all the existing algo-rithms, and the radiance data processed to provideseveral different cloud data products that could beused for the research mentioned above. As morepointed questions have been asked involving clouds,the ISCCP product line has continued to expand, nowincluding radiative flux profiles, cloud particle sizesand several subsets concerning specific cloud sys-tem types (convective tracking, cyclone tracking,pattern recognition analysis for tropics andmidlatitudes). The ISCCP products have now devel-oped into one of the longest time records of globalcloud variations and have become part of the GlobalClimate Observing System (GCOS).

ISCCP CELEBRATES 25TH ANNIVERSARY

13May 2008

Volume contributions to long-time change/linear fit during 1979–2005.

Tropical (25S–25N) annual mean precipitation (solid lines) andtemperature (dashed lines) anomalies. Sp and STs denote linearchanges for precipitation and temperature anomalies, respectively.R and Rdt represent the correlations between precipitation andtemperature anomalies with and without the respective linear changes.

Two recent papers based upon the GEWEXGlobal Precipitation Climatology Project(GPCP) 27-year data set highlight the strongtropical but weak global trends for increas-ing precipitation, as well as a correlationwith increasing surface temperature. The fol-lowing abstracts and papers provide morein-depth analyses of the trends and correla-tions derived from the GPCP data sets.

Relationships Between Global Precipitation and Sur-Relationships Between Global Precipitation and Sur-Relationships Between Global Precipitation and Sur-Relationships Between Global Precipitation and Sur-Relationships Between Global Precipitation and Sur-face Temperature on Interannual and Longer Timeface Temperature on Interannual and Longer Timeface Temperature on Interannual and Longer Timeface Temperature on Interannual and Longer Timeface Temperature on Interannual and Longer TimeScales (1979–2006).Scales (1979–2006).Scales (1979–2006).Scales (1979–2006).Scales (1979–2006). Adler, R. F., G. Gu, J. Wang,G. J. Huffman, S. Curtis, and D. Bolvin (submitted toJournal of Geophysical Research-Atmospheres, June 2008).

Summary/Abstract: Associations between global and re-gional precipitation and surface temperature anomalieson interannual and longer time scales are explored forthe period of 1979–2006 using the GPCP precipita-tion product and the National Aeronautics and SpaceAdministration Goddard Institute for Space Studiessurface temperature data set. Positive (negative) corre-lations are generally observed between these two variablesover tropical oceans (lands). The El Niño SouthernOscillation (ENSO) is the dominant factor in theseinterannual, tropical relations. The ratios between thelinear changes in zonal mean rainfall and temperatureanomalies over the period are estimated. Globally, thecalculation results in a 2.3 percent/oC precipitationincrease, although the magnitude is sensitive to smallerrors in the precipitation data set and to the lengthof record used for the calculation (bottom figure).

Tropical Rainfall Variability on InterannualTropical Rainfall Variability on InterannualTropical Rainfall Variability on InterannualTropical Rainfall Variability on InterannualTropical Rainfall Variability on Interannualto-Interdecadal/Longer-time Scales Derivedto-Interdecadal/Longer-time Scales Derivedto-Interdecadal/Longer-time Scales Derivedto-Interdecadal/Longer-time Scales Derivedto-Interdecadal/Longer-time Scales Derivedfrom the GPCP Monthly Product.from the GPCP Monthly Product.from the GPCP Monthly Product.from the GPCP Monthly Product.from the GPCP Monthly Product. Gu,G., R. F. Adler, G. Huffman, and S.Curtis, 2007. J. Climate, 20, 4033–4046.

Summary/Abstract: Global and large regional rainfallvariations and possible long-term changes are examinedusing the 27-year (1979–2005) GPCP monthly dataset. Emphasis is placed on discriminating among varia-tions due to ENSO, volcanic events, and possiblelong-term climate changes in the tropics. Although theglobal linear change of precipitation in the data set isnear zero during the time period (top figure), anincrease in tropical rainfall is noted in the data set,with a weaker decrease over the Northern Hemispheremiddle latitudes. Focusing on the tropics (25S–25N),the data set indicates an upward linear change (0.06 mmday-1/decade) and a downward linear change (–0.01 mmday-1/decade) over tropical ocean and land, respectively.This corresponds to about a 5.5 percent increase (ocean)and 1 percent decrease (land) during the entire 27-yeartime period (middle and bottom figure).

Annual mean global rainfall anomalies over ocean, land, and both oceanand land. Also shown are the estimated slopes of the linear fits.

GPCP 27-Year Record Shows Regional/Global Trends and Correlation With Temperature

May 200814

Geostationary Earth Orbit Satellite (GOES)-----10 movedto 60E; these data will be contributed toward theInternational Satellite Cloud Climatology Project (ISCCP).B. J. Sohn reported on the development of a Koreangeostationary weather/communication satellite (COMS) tobe launched in 2009. T. Iguchi presented the status ofthe JAXA Earth observation program, including Green-house Gases Observing Satellite (GOSAT) (2008 launch),a cloud profiling radar for the EarthCare mission anda dual-frequency precipitation radar for the GlobalPrecipitation Mission (GPM). P. van Oevelen describedthe ESA Earth Explorer missions, including Gravityfield and steady-state Ocean Circulation Explorer (GOCE)(2008 launch) and Soil Moisture and Ocean Salinity(SMOS) (2008 launch). Y. Govaerts presented thestatus of EUMETSAT satellite operations.

A special briefing on the U.S. Department of EnergyAtmospheric Radiation Measurement (ARM) programwas presented by J. Mather, who described the newARM Mobile Facility (AMF) that has been deployedfor two field experiments, notably for the African Mon-soon Multidisciplinary Analysis (AMMA) Project incoordination with measurements from the Geostation-ary Earth Radiation Budget (GERB). AMF goes toChina in 2008; like the rest of the AMF sites, in-cludes active profiling sensors for clouds, aerosols, andatmospheric properties. ARM is creating a Best Esti-mate Data Set for Climate Modellers that will mergemany of the clouds and radiation products into acommon product. W. Rossow reported on the Work-ing Group on Data Management and Analysis activitiesduring the past year (see the report on page 10 of theFebruary 2008 GEWEX News).

Two guest scientific lectures were presented. M. Yamasoedescribed a field experiment in Brazil to investigate thecoupling between biomass burning and aerosol pro-duction with a consequent reduction of surface solarheating and vegetation activity. This experiment wasconducted in the Amazon Reserva Biologica do Jaru inAugust 2007. Early conclusions are that, although thefire-produced aerosols do reduce solar radiation at thesurface (which reduces sensible and latent fluxes), theeffects on vegetation activity were much more complex.L. Machado reported on the use of high time resolu-tion geostationary satellite cloud observations in severeweather nowcasting: the satellite images can detect andtrack the motions of large storm systems and alsomeasure their growth rate, which has improved short-range precipitation forecasts.

R. Adler reported on the status of the Global Precipi-tation Climatology Project (GPCP). While productionof Version 2 products continues routinely and is up todate, studies continue to develop improvements to beimplemented in Version 3. Such improvements con-cern precipitation underestimates in mountainous areas,modernizing the microwave algorithm to increase timesampling frequency to once or twice daily and incor-porating more recent precipitation measurements (such

18th Meeting of the GEWEX Radiation Panel

9–12 October 2007Buzios, Brazil

William B. RossowThe City College of New York, NY, USA

The GEWEX Radiation Panel (GRP) meeting was hostedby Luiz A. T. Machado, of the Centro de Previsao deTempo e Estudos Climaticos (CPTEC) Instituto Nacionalde Pesquisas Espaciais (INPE). The main goals of themeeting were to review plans for completing the dataproduct assessments, discuss plans for reprocessing allglobal data products, review the progress of the SeaFluxand LandFlux activities, and discuss creating a polardata initiative. Discussion also focused on assessing thegoals and overall progress of GRP and its projects andon future directions, as the chairmanship of GRP ispassed from William Rossow to Chris Kummerow.

W. Rossow opened the meeting with a review of GRPobjectives that he outlined in 2001 as incoming chair-man: (1) fostering advances in remote sensing analysis;(2) evaluating global climate model (GCM) radiative fluxcodes; (3) advancing 3-D radiation modeling to investi-gate scale-dependent coupling of the atmosphere andland surface; (4) fostering studies of cloud and aerosolinteractions; (5) fostering studies of clouds and precipita-tion; (5) developing remote sensing-based inferences ofocean surface turbulent fluxes; (6) developing remotesensing-based inferences of land surface turbulent fluxes;(7) advancing analysis of natural climate variability andfeedback; (8) diagnosing atmospheric energy and watertransports; and (9) diagnosing oceanic energy and watertransports. Progress has been made on all of these objec-tives, especially on objectives 2, 3, 5, 8, and 9.

C. Kummerow followed with his ideas for GRP activi-ties in the next few years. Continuing work on globaldata projects could be usefully directed towards objec-tives 4 and 5—as well as 7, 8, and 9—by producingmerged products that bring together the separateparameter-centric products at the highest feasiblespace-time resolution for global process studies. Theplanned reprocessing of the global data productsshould focus on improving “long-time-record” qual-ity so they can be used more confidently for climatemonitoring studies. This activity should begin to makeplans for the long-term stewardship of these products,while continuing to lead efforts to convert researchanalyses to climate operations.

Reports from INPE and the Korea Aerospace ResearchInstitute, as well as reports from the Japan AerospaceExploration Agency (JAXA), the European Space Agency,and the European Organization for the Exploitation ofMeteorological Satellites (EUMETSAT), were given.Brazil recently took over data collection when theNational Oceanic and Atmospheric Administration

Meeting/Workshop Reports

15May 2008

as the 10-year Tropical Rainfall Measuring Missionrecord) to anchor the product’s time record, and in-creasing the sampling homogeneity of the gauge dataset used to produce the products. Version 3 (2009)will have smaller time sampling intervals (at least daily)and space sampling intervals (at least 50 km).

J. Schulz, on behalf of U. Schneider, reported onactivities at the Global Precipitation Climatology Cen-tre (GPCC). Several new products have been producedfrom the gauge collection, including ones that havemeasurements from the maximum number of sites andfrom the most homogeneous collection of sites. Thelatter now covers a 50-year period with 9,400 sites. P.Arkin reported on an activity to evaluate new high-resolution precipitation products organized by theInternational Precipitation Working Group of the Co-ordination Group for Meteorological Satellites (CGMS).T. Iguchi described a new high resolution (10 km, 1hr) precipitation product being produced in Japan.

J. Schulz reported on progress in producing improvedglobal water vapor products, particularly activities atthe EUMETSAT Climate Monitoring Satellite Appli-cation Facilities (CMSAF). The current focus is on theanalysis of combinations of newer instruments. TheAdvanced TIROS Operational Vertical Sounder (ATOVS)product provides daily global temperature and humid-ity profiles at 90-km intervals; this product is currentlybased on the High Resolution Infrared Radiation Sounder(HIRS)/Advanced Microwave Sounding Unit (AMSU)combination; efforts are underway to incorporate InfraredAtmospheric Sounding Interferometer (IASI) and GPS mea-surements. In the next phase of the CMSAF,,,,, a long-term,global water vapor product will be produced.

D. Barber, a new GRP member, described research onsea ice climate change and provided some backgroundinformation on International Polar Year (IPY) plansand activities. In addition to the widely publicizedindicators of dramatic sea ice changes there are alsonoticeable changes in the atmospheric weather sys-tems. As part of IPY, Canada has planned a number ofambitious field campaigns over the next few years,including the Circumpolar Flaw Lead Study, HudsonBay ice studies, research on the impact of these changesin partnership with Inuit communities, and participa-tion in other IPY projects. D. Barber suggested thatthe GRP data products could be useful in supportingthese studies and that GEWEX might consider a fieldstudy, like the Baltic Sea Experiment or the MackenzieGEWEX Study for the Hudson Bay region.

T. Uttal described other IPY activities underway, in-cluding a network of observing sites with cloud radarsystems, plans for organizing standard data sourcesinto a special Arctic-focused subset, a polar aerosoloptical depth study, and a polar aerosol-chemistry-meteorology study. She highlighted the fact that mostof these projects did not employ satellite observations,focusing totally on surface measurements, and sug-

gested that a focused GRP initiative might prove use-ful to bring the satellite products together with theextensive surface observations being collected for IPY.GRP members decided to undertake a small pilotactivity to extract a subset of the GRP global productscoincident with the main surface sites active for IPYand cover a time period when observations are avail-able from both CloudSat/the Cloud-Aerosol Lidar andInfrared Pathfinder Satellite (Calipso) and the Atmo-spheric Infrared Sounder (AIRS)/IASI. GRP will alsoorganize a workshop to advertise this data collection andfoster studies using it and the surface measurements.

D. Winker presented an update on the status andactivities of the Calipso and CloudSat missions, whichhave received approval to extend the original 22-monthmission through 2011. A merged Calipso-CloudSatcloud mask is nearing release and the next release ofbasic Calipso products is being prepared. An intrigu-ing result from Calipso is a stronger than expectedeffect of “plate-like” cloud/precipitation particles onthe lidar returns when pointed at nadir, which isespecially notable in the polar regions.

C. Stubenrauch, a new GRP member, described re-search on the vertical distribution of cirrus clouds andatmospheric properties obtained from infrared sounderinstruments, especially contrasting the changes from“channel radiometers” like HIRS to spectrometers likeAIRS/IASI. Analyses of these products are now provid-ing information about the microphysical properties ofcirrus and their association with upper tropospherichumidity and how both of these are influenced byatmospheric motions from convective to planetary scales.

W. Rossow summarized the status of ISCCP, now inits 25th year (see articles on page 11 and 12). Allproducts have been delivered through June 2006 andprocessing is underway on the next year of data. Newfunding will allow a switch of the processing from the30-km-sampled radiances to a 10-km-sampled version,thereby increasing the value of the ISCCP products forcloud process studies. For the first time, the radiancedata being contributed to ISCCP come from moresatellites than needed—the number could soon be 10.

C. Stubenrauch reported on the continuing cloudproduct assessment activity, a comprehensive set ofresults that is beginning to emerge, including thetotal global cloud amount, its partitioning amonglow/middle/high levels, geographic distribution, andseasonal and diurnal variations. There are systematicdifferences in total cloud amount but it is under-stood that these differences depend on variations incloud detection sensitivity among different instru-ments. Calipso results will be examined this comingyear. A third workshop planned in 2008 will com-pare other cloud properties.

W. Rossow reported on the status of the Global Aero-sol Climatology Project on behalf of M. Mishchenko.

May 200816

Operational Environmental Satellite System (NPOESS)program removed the solar irradiance instrument, put-ting the future of these measurements in doubt.

L. Oreopoulus reported on the status of the ContinuousIntercomparison of Radiation Codes (CIRC) Project.CIRC, which is sponsored by ARM, is evaluating GCMradiation codes by the Intercomparison of RadiationCodes used in Climate Models (ICRCCM). CIRC isworking to establish an online capability for testingsuch radiative transfer codes by providing synthetic andobservation-based test cases as well as the fluxes calcu-lated by a few state-of-the-art line-by-line codes. ICRCCMhad developed an incomplete set of synthetic test cases,but another observation-based set is being developedfrom ARM site observations that provide a complete setof measured atmospheric properties—including clouds—together with directly measured fluxes at the surface.

P. Stackhouse reported that all Surface Radiation Bud-get (SRB) project products have been delivered throughJune 2005. Minor changes to the shortwave algorithmwere implemented during the past year to better ac-count for low sun angles in the polar regions and touse a more accurate solar emphemeris, as well to re-port clear sky aerosol radiative effects. The SRB productsare being evaluated as part of the Radiation Assess-ment, along with products from ISCCP, the EarthRadiation Budget Experiment (ERBE), the Center forEnvironmental Remote Sensing (CERES), GERB, andthe Baseline Surface Radiation Network (BSRN). Onenotable result of the assessment is that the differencesin cloud radiative effect calculated by SRB and ISCCP-FD are about three times smaller than the differencesamong the 20 Intergovernmental Panel on ClimateChange climate models.

E. Dutton reported that BSRN is now comprised of60 active stations. There are now 3,850 station-monthsof data archived at 1-min resolution, an average of 8.2-years per site for 39 sites. Two issues have beeninvestigated during the past year: (1) it was found thatphotosynthetically active radiation (PAR) is not pre-cisely or even well defined, and (2) the SurfaceOcean-Lower Atmosphere Study (SOLAS) is not spe-cifically collecting PAR measurements. In addition,current PAR measurements are being made with ill-defined commercial instruments. Hence, if BSRN (andothers) are to collect PAR data sets, a standard definitionwill have to be developed. BSRN is working with SOLASto define measurement specifications and procedures.

C. A. Clayson reported that two SeaFlux Project work-shops were held in 2007 and that there is continuedprogress towards completing the comparison of a com-mon year of global products, based on “old” and“new” instruments; comparisons for 1999 not onlyallow for the overlap of different kinds of instrumentsbut have a good collection of in situ surface flux mea-surements for continual improvement of flux formulae.

The aerosol climatology (monthly mean values of op-tical depth and size index over global oceans) nowcovers the period from August 1981 through June2005; this record will be extended to June 2007 assoon as the ISCCP processing is completed. See M.Mischenko's May 2007 article in GEWEX News.

B. J. Sohn presented comparisons of water budgetsinferred from satellite observations and the weatherreanalyses. The intensity of the Hadley-Walker circu-lation has a well-known seasonal variation but mayalso begin to change in a warming climate. This studyaims to develop methods for deriving the water vaportransports by the general circulation and to relatevariations in changes in other water-related quantitiessuch as precipitation, evaporation, and clouds. Bothregional studies (e.g., Asian monsoon) and global stud-ies are underway. The mean water vapor transportsdetermined in the reanalysis data sets agree well withthose inferred from microwave-based precipitation-evapo-ration differences. These SSM/I-based results and thereanalyses all show an increase in the wintertime Hadleycirculation strength over the past decade, whereas theWalker circulation strength shows a weakening.

R. Chahalan reported on research involving 3-D radia-tive transfer under two groups, one focusing on clouds(I3RC) and one focusing on vegetation canopies (RAMI).I3RC is completing its Phase 3 experiments comprisedof 12 models to evaluate 3-D photon transport bycloud scattering (no absorption). As a result, severalcodes considered to be the “industry standard” have beenreleased on a web site for other researchers to use.

R. Chahalan also reported on the status of researchbeing done since 2003 with measurements of the solarirradiance from the Solar Radiation and Climate Ex-periment (SORCE). The total solar irradiance valueobtained from SORCE (1,361 Wm–2) is 5 Wm–2 lowerthan from the Active Cavity Radiometer IrradianceMonitor (ACRIM) series of instruments, which werethemselves lower than earlier measurements by aboutthe same amount. This has triggered intense calibra-tion and instrument characterization studies to determinethe cause or causes of this difference. National Insti-tute of Standards and Technology (NIST) calculationsof the aperture diffraction in ACRIM—already deter-mined for the Total Irradiance Monitor (TIM) onSORCE—suggest a reduction of its solar irradiancevalues by nearly 2 Wm–2. The SORCE mission alsostarted the first systematic spectral measurements ofsolar irradiance, confirming that there is a more com-plex and larger variability of the sun at wavelengthsshorter than visible, which has implications for varia-tions of the upper atmospheric chemistry. Althoughthe SORCE mission was recently approved to continueto 2011, the launch of the next instrument to measuretotal (but not spectral) solar irradiance on the GLORYmission has suffered some delay and is now scheduledfor 2009. More importantly, the National Polar-orbiting

17May 2008

Version 1 of a new sea surface temperature (SST)product that resolves diurnal and weather-scale varia-tions of skin temperatures has been produced and isbeing tested. Most previous SST products were esti-mates of bulk temperature and provided only thevariations on weekly to monthly time scales.

W. Rossow reported on activities of the LandFlux projectto obtain turbulent fluxes over land (and ice) surfaces.The first international workshop was held in May2007. After reviewing possible methodologies and thestatus of land remote sensing more generally, the workshopparticipants agreed that future work should pursuetwo parallel pathways: (1) systematic data products(global, long-term) for the basic properties of the landsurface (albedo, emissivity, temperature, some vegeta-tion indicator, possibly soil moisture information) needto be evaluated and brought up to the same standardas other GRP products; and (2) the different methodsfor estimating surface turbulent fluxes need to com-pared and the differences investigated.

A consensus was reached that a main activity of GRPwould continue to be the set of projects leading to acomplete description of weather-to-climate scale varia-tions of the global energy and water cycle. An assessmentof more mature products (precipitation, radiation, clouds,and aerosols) should be completed. With SeaFlux near-ing readiness to produce a new product, the focusshould now be on bringing LandFlux to the samestatus using polar initiative activities to include frozensurface processes. The coordinated reprocessing of allcurrent global products will focus not only on increas-ing the physical consistency of the products (usingcommon ancillary data sets) but also on reducing spu-rious variations in the long-term record (based on theassessment results), moving these products towards climatedata record quality.

GRP will continue to work with space agencies andinternational groups to define a climate observing sys-tem and climate data records. With these continuingactivities as a foundation, more emphasis now needs tobe focused on determining atmospheric and oceanictransports of energy and water, which should alsoinvolve further interaction with general circulationmodeling groups. It was concluded that a smaller,more focused working group needs to be organized toinvestigate cloud processes, aerosol interactions, andprecipitation using the global satellite products andfield experiment data sets.

The 2008 GRP meeting will be hosted by B. J. Sohnand the Seoul National University in South Korea on14–17 October 2008.

Approximately 60 experts gathered in the FoothillsLaboratory of the National Center for AtmosphericResearch to attend the workshop, which was spon-sored by GEWEX, the U.S. National Oceanic andAtmospheric Administration, and U.S. National Aero-nautics and Space Administration. The goal of theworkshop was to entrain United States experts andprograms as well as incorporate the interests of Canadaand, possibly, Mexico and South America in anassessment of the potential needs and benefits of afocused research effort on the mountain hydroclimateof western Cordillera in North America. Workshopparticipants were asked to assess the state of knowl-edge of the mountain hydroclimate and developpriority science questions to be addressed in a large-scale study. They were also invited to comment onthe extent to which existing research and opera-tional programs address these issues and any missingelements that could be addressed by a new initiative.

On the observation and modelling of orographicprecipitation, significant challenges remain in simu-lating both cold season and warm season orographicprecipitation. These challenges are partly due to thedifficulty in representing scale interactions (i.e., theinfluence of large-scale circulation on regional pre-cipitation, and the influence of local condensationand microphysical processes on upstream flow sta-bility), and the inadequate representation in modelsof processes such as embedded convection in mesos-cale clouds. Although higher spatial resolution isdesired, physics parameterizations are resolution de-pendent, and the appropriate scale for modellingand analysis of the mountain hydroclimate is notwell defined. These difficulties also exist for regionalanalyses of the mountains, where inequitable spatialdistribution of observations and a lack of boundarylayer data to constrain forward modelling add to thedifficulties. The analysis of in situ measurementsand remote sensing of precipitation also face specificchallenges in the mountains because of scaling, tech-nical limitations (e.g., radar beam blockage andovershoot), and issues with deployment and mainte-nance that warrant special considerations.

On the observation and modelling of surface/subsur-face and ecological processes, much progress has beenmade with one-dimensional models to simulate hy-drological and ecological processes; however, challenges

North American MountainHydroclimate Workshop

17–19 October 2007Boulder, Colorado, USA

Rick Lawford1 and L. Ruby Leung2

1 International GEWEX Project Office, Silver Spring,Maryland, USA; 2 Pacific Northwest National Laboratory,Richland, Washington, USA

The GEWEX Radiat ion Panel Assessment ofGlobal Precipitation Products is available at:

http://wcrp.wmo.int/documents/AssessmentGlobalPrecipitationReport.pdf.

May 200818

remain in translating skill from point modeling tocorrectly capture the simultaneous spatial distributionof multiple variables such as snow and streamflow.Since many processes are tightly coupled, they shouldbe studied with models and observations from stra-tegically placed ground-based instrument clusters andsatellite data. These complex studies are necessaryto develop a systems approach to understanding therelationships between climate patterns, landscapeattributes, and spatially distributed hydrological andecological processes. Monitoring land water balanceand ecosystem health is increasingly important inthe context of climate change, and this requiresadvances in both in situ and remote sensing mea-surements and long-term commitments to themaintenance of these observational systems.

A number of recent field projects conducted in theUnited States, Canada, South America, and Europethat have focused on orographic processes were pre-sented at the workshop. A common need exists forgreater temporal frequency and spatial sampling tounderstand process evolution and response to forcings,and identify specific model deficiencies that guidedata requirements. The coordination of the interestsand needs of subdisciplines, related science commu-nities, and potential partners can maximize results.

Progress has been made on hydrologic predictionsand water applications across a range of forecast leadtimes using statistical and physically based hydro-logic models with inputs from weather forecasts,seasonal climate prediction, and long-term climateprojections. A particular challenge for hydrologicprediction in the mountains is associated with un-certainty in precipitation forecasts, which is dependenton both the spatial and temporal scale. Ongoingresearch efforts are assessing the benefits of distrib-uted hydrologic models versus lumped models orstatistical models in providing increased simulationor forecast accuracy. Physically based tools may haveimportant advantages in the context of an evolvingclimate system. For the western United States, warmingalone may lead to myriad changes that will chal-lenge water management including rain versus snowratios, storm intensities, snowmelt and streamflowtiming, flood risk, and longer growing seasons.

Based on the reports from the discussion groups,there is a clear consensus for conducting a focusedstudy on the hydroclimate of the mountains of westernNorth America, especially in view of the potentialimpacts of climate change on these areas and ourlimited ability to predict hydroclimate conditions inthese environments. Specific science questions thatrequire more attention range from climate predic-tion to climate impacts on mountain ecology. Inparticular, there is a need to understand how cli-mate variability and change associated with warming

temperatures affect the hydrology and ecology ofthe mountain regimes and the evolution of droughtconditions, as well as the implications of climatechange for seasonal predictions. There is also a growingneed to improve our ability to predict the waterand energy cycle components in complex terrain onseasonal time scales. This predictive capability canonly be improved by understanding the large-scalewater balance and its variability in mountainousterrain by improved measurement programs that willlead to enhanced data sets with error estimates foruse in improving hydrologic models and predic-tions. Although there are a number of ongoing studiesin western Cordillera, most of them are indepen-dent. A jointly planned effort would make asubstantial contribution to better coordination. Thelack of data collection programs and comprehensiveunified representative data has limited our ability toevaluate the error characteristics of climate and hy-drologic models for model development.

There was considerable discussion on the scope of anew North American mountain project and a planwas proposed that would include an area rangingfrom a large river basin to the entire western UnitedStates with a small number of embedded intensiveresearch basin networks (e.g., along topographictransects) that would acquire detailed, high-resolu-tion hydrological and ecological data. Ideally, themeasurement program would consider the full an-nual cycle and continue for 10 years.

In terms of science, there is a need to study therelationships between topography, precipitation, andrunoff in complex terrain. A link to the Intergovern-mental Panel on Climate Change assessment activitiesis also important. This research would be directedto improving climate monitoring and prediction inthe mountains with a focus on analyses and modelsto understand the implications of variability andchange for mountain hydrology and ecology. It wasalso recognized that mountains posed a major prob-lem for Earth system modelling and the developmentof a regional Earth system model that fully repre-sents mountain processes with built-in diagnosticand analysis components could serve as a majorlonger-term goal for this work. It is also importantto understand the full range and role of scale inter-actions in a mountain environment—that is, theupscaled effects of mountains and the downscaledeffects of large-scale variability and change on re-gional and local scale mountain processes.

It was agreed that the workshop organizers explore thepossibility of developing a concept paper as a means toseek funding support for a project of the scope outlinedhere. The workshop was videotaped by Greg Greenwoodand the video and workshop presentations are available at:http://www.eol.ucar.edu/projects/cppa/meetings/200710/.

19May 2008

2nd Meeting of the International SoilMoisture Working Group

14–15 November 2007Beijing, China

The 2nd International Soil Moisture Working Group(ISMWG) Meeting was hosted by the Institute ofApplied Physics of the Chinese Academy of Sciencesin Beijing, with a total of 20 registered participantsplus 15 students and post-doctorals. This meetingwas intended to increase the awareness of workinggroup activities among those institutions and scien-tists operating soil moisture networks in Asia, aswell as to build upon the outcomes of the FirstISMWG meeting. Both the first and the secondworkshop sparked interest among various types ofparticipants and institutions dealing with in situ soilmoisture and resulted in a very cooperative spirit.The ISMWG has two main objectives: To supportthe development of an in situ global soil moisturenetwork, and to support international cooperationin research and applications in support of soil mois-ture satellite missions.

One of the first key results in 2007 was that a data-hosting center would be established by the Institutode Meteorologia in Lisbon, Portugal, with the sup-port of the European Space Agency (ESA) throughthe Soil Moisture and Ocean Salinity (SMOS) mis-sion project. This data-hosting center will supportthe soil moisture data collection activities that areorganized in the framework of the SMOS Calibra-tion-Validation activities, as well as act as the globaldata-hosting center for other soil moisture collectionactivities.

The data hosting center will open in 2008. Besidesthe development of a web-based data hosting system,the center will initiate an inventory of the require-ments regarding soil moisture data collection,dissemination, etc. through a questionnaire sent outto an extensive list of potential collaborators. Thecenter will act as a focal point for working groupactivities and will make information on soil mois-ture measurements and installation protocols availableto a wider audience.

Some of these measurement and network design re-quirements have been established since the firstISMWG meeting and will be disseminated throughthis system. The open access data policy of thenetwork is one of the key pillars in establishing aglobal network of soil moisture measurements and isreceived favorably by many of the currently existingoperational regional networks.

Peter J. van OevelenInternational GEWEX Project Office, Silver Spring, Mary-land, USA

GEWEX NEWS

Published by the International GEWEX Project Office

Peter J. van Oevelen, DirectorDawn P. Erlich, Editor

Cathryn E. Kulat, Assistant Editor

Mail: International GEWEX Project Office8403 Colesville Rd, Suite 1550Silver Spring, MD 20910, USA

Tel: 240-485-1855Fax: 240-485-1818

E-mail: gewex@gewex.orgWeb Site: http://www.gewex.org

GEWEX/WCRP Meetings Calendar

2–6 June 2008—44444ththththth PAN-GCSS Meeting: Advances on Model- PAN-GCSS Meeting: Advances on Model- PAN-GCSS Meeting: Advances on Model- PAN-GCSS Meeting: Advances on Model- PAN-GCSS Meeting: Advances on Model-ling and Observing Clouds & Convectionling and Observing Clouds & Convectionling and Observing Clouds & Convectionling and Observing Clouds & Convectionling and Observing Clouds & Convection—MeteoFrance, Toulouse,France.

2–6 June 2008—NEESPI Science Team MeetingNEESPI Science Team MeetingNEESPI Science Team MeetingNEESPI Science Team MeetingNEESPI Science Team Meeting—Helsinki, Fin-land.

25–27 June 2008—LOCO/Watch WorkshopLOCO/Watch WorkshopLOCO/Watch WorkshopLOCO/Watch WorkshopLOCO/Watch Workshop—De Bilt, The Neth-erlands.

7–11 July 2008—1010101010ththththth Science and Review Workshop for the Science and Review Workshop for the Science and Review Workshop for the Science and Review Workshop for the Science and Review Workshop for theBaseline Surface Radiation NetworkBaseline Surface Radiation NetworkBaseline Surface Radiation NetworkBaseline Surface Radiation NetworkBaseline Surface Radiation Network—De Bilt, The Netherlands.

9–13 July 2008—1515151515ththththth International Conference on Clouds and International Conference on Clouds and International Conference on Clouds and International Conference on Clouds and International Conference on Clouds andPrecipitation (ICCP2008)Precipitation (ICCP2008)Precipitation (ICCP2008)Precipitation (ICCP2008)Precipitation (ICCP2008)—Cancun, Mexico.

23–25 July 2008—International Satellite Cloud Climatology ProjectInternational Satellite Cloud Climatology ProjectInternational Satellite Cloud Climatology ProjectInternational Satellite Cloud Climatology ProjectInternational Satellite Cloud Climatology Project2525252525ththththth Anniversary Symposium Anniversary Symposium Anniversary Symposium Anniversary Symposium Anniversary Symposium—NASA, GISS, New York, NY, USA.

25–29 August 2008—GEWEX Executive MeetingGEWEX Executive MeetingGEWEX Executive MeetingGEWEX Executive MeetingGEWEX Executive Meeting—Silver Spring,Maryland, USA.

15–17 September 2008—CEOP International Planning Meet-CEOP International Planning Meet-CEOP International Planning Meet-CEOP International Planning Meet-CEOP International Planning Meet-inginginginging—Geneva, Switzerland.

22–24 September 2008—55555ththththth GEWEX Radiation Panel Working GEWEX Radiation Panel Working GEWEX Radiation Panel Working GEWEX Radiation Panel Working GEWEX Radiation Panel WorkingGroup on Data Management and Analysis MeetingGroup on Data Management and Analysis MeetingGroup on Data Management and Analysis MeetingGroup on Data Management and Analysis MeetingGroup on Data Management and Analysis Meeting—Hong Kong,China.

22–24 September 2008—122222ththththth Session of the Working Group on Session of the Working Group on Session of the Working Group on Session of the Working Group on Session of the Working Group onCoupled ModellingCoupled ModellingCoupled ModellingCoupled ModellingCoupled Modelling—Paris, France.

29 September–2 October 2008—33333rdrdrdrdrd Session of the WCRP Ob- Session of the WCRP Ob- Session of the WCRP Ob- Session of the WCRP Ob- Session of the WCRP Ob-servation and Assimilation Panelservation and Assimilation Panelservation and Assimilation Panelservation and Assimilation Panelservation and Assimilation Panel—Boulder, Colorado, USA.

14–17 October 2008—GEWEX Radiation Panel MeetingGEWEX Radiation Panel MeetingGEWEX Radiation Panel MeetingGEWEX Radiation Panel MeetingGEWEX Radiation Panel Meeting—SouthKorea.

3–7 November 2008—Working Group on Numerical Experimen-Working Group on Numerical Experimen-Working Group on Numerical Experimen-Working Group on Numerical Experimen-Working Group on Numerical Experimen-tation/GEWEX Modelling and Prediction Panel Meetingtation/GEWEX Modelling and Prediction Panel Meetingtation/GEWEX Modelling and Prediction Panel Meetingtation/GEWEX Modelling and Prediction Panel Meetingtation/GEWEX Modelling and Prediction Panel Meeting—Montreal,Canada.

19–23 January 2009—GEWEX Scientific Steering Group Meet-GEWEX Scientific Steering Group Meet-GEWEX Scientific Steering Group Meet-GEWEX Scientific Steering Group Meet-GEWEX Scientific Steering Group Meet-inginginginging—Irvine, California, USA.

14–28 August 2009—614–28 August 2009—614–28 August 2009—614–28 August 2009—614–28 August 2009—6ththththth International Scientific Conference on International Scientific Conference on International Scientific Conference on International Scientific Conference on International Scientific Conference onthe Global Energy and Water Cycle, 2the Global Energy and Water Cycle, 2the Global Energy and Water Cycle, 2the Global Energy and Water Cycle, 2the Global Energy and Water Cycle, 2ndndndndnd iLEAPS Science Con- iLEAPS Science Con- iLEAPS Science Con- iLEAPS Science Con- iLEAPS Science Con-ference, and joint sessions—Melbourne, Australia.ference, and joint sessions—Melbourne, Australia.ference, and joint sessions—Melbourne, Australia.ference, and joint sessions—Melbourne, Australia.ference, and joint sessions—Melbourne, Australia.

For a complete listing of meetings, see theFor a complete listing of meetings, see theFor a complete listing of meetings, see theFor a complete listing of meetings, see theFor a complete listing of meetings, see theGEWEX web site: http://www.gewex.orgGEWEX web site: http://www.gewex.orgGEWEX web site: http://www.gewex.orgGEWEX web site: http://www.gewex.orgGEWEX web site: http://www.gewex.org

May 200820

Comparison of annual averages (March 2000 to February 2004) of differences between the effective solar surface albedo (left:dimensionless ratio of upward to downward clear-sky solar fluxes) and emission fields (right: in Wm–2) used in SRB and CERES tothose of the ISCCP. See article by E. Raschke et al. on page 11.

GEWEX Radation Data Assessment Shows Inconsistencies in Ancillary Data

Space/time-averaged heating profiles, Case 1b: South China Sea Monsoon Experiment (SCSMEX)-South Enhanced Sounding Arrays(SESA) regions. Profiles for different heating terms are obtained from five different satellite algorithms [i.e., Convective StratiformHeating (CSH), Hydrometeor Heating (HH), Goddard Profiling Heating (GPROF), Spectral Latent Heating (SLH), and PrecipitationRadar Heating (PRH)]. Q

1 profiles from Colorado State University's (CSU) diagnostic calculations are presented for two different

averaging areas (i.e., DIAG from within SESA sounding arrays and CSU from SESA study area rectangular gridded arrays]. Satellite-derived Q

R profiles from CSU are also associated with gridded arrays. See article by Wei-Kuo Tao on page 8.

Retrieved Latent Heating from the Tropical Rainfall Measuring Mission