precipitation analyses for climate applications pingping xie 2013.08.14
TRANSCRIPT
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Precipitation AnalysesPrecipitation Analysesfor Climate Applicationsfor Climate Applications
Pingping XiePingping Xie
2013.08.14.2013.08.14.
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ObjectivesObjectives
• History and current status
• Illustrate some applications
• List products available
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CPC Started as CACCPC Started as CAC
• Climate Analysis Center created 1979
• The CAC missions include the real-time monitoring of climate anomalies along with diagnostic studies relating the anomalies to historical conditions
• Two Branches• Diagnostics Branch • Prediction Branch
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The Diagnostics BranchThe Diagnostics Branch• Branch Chief Gene Rasmusson
• Major projects included• Ocean (R.W. Reynolds)• Precipitation and tropical Convection (P.A. Arkin)• Precipitation / Temperature Anomaly (C.F.
Ropelewski)• ENSO Evolution (G. Rasmusson)
• Collecting and constructing observation data key to the success of the projects
• Construction of climate data sets started • Global SST• OLR• Global Precipitation• Station Precipitation and Temperature over Land
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Early Efforts Early Efforts in constructing Precip Data Setsin constructing Precip Data Sets
• Station Data • 1979 Started archiving GTS daily station
reports• 1984 Created CAMS (Climate Anomaly
Monitoring System) for monthly precipitation and temperature
• Satellite Estimates• 1979 Developed GPI (GOES Precipitation
Index) technique to derive precipitation estimates from IR data
• 1981 Began routine production of GPI using histograms from GOES
IR• 1982 Started the OLR archive • 1985 Hosted the workshop initiated the
GPCP• 1986 GPCP launched
GPI covers the tropical beltGPI used for climate monitoring
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The GPI Global PrecipitationThe GPI Global PrecipitationSample for July 2007Sample for July 2007
• Successful depiction of tropical precipitation• Available only over tropics (40oS-40oN)• Poor performance for non-convectiive precipitation• Smooth spatial structure
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SSM/I SSM/I Improves Precipitation EstimatesImproves Precipitation Estimates
• Time • 1987 ~
• Scientific Requirements• Global precipitation data with complete coverage and improved quality
• Technical Developments • PMW instruments aboard Special Sensor Microwave / Imager
• Products • Algorithms / Products developed by many groups• Emission-based algorithms over ocean • Scatter-based algorithms over land • Monthly precipitation estimates on 2.5olat/lon • Available 3-4 months afterwards till ~1999• Real-time monitoring impossible• CAC utilized SSM/I-based precipitation estimates for diagnostics
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The SSM/I-Based PrecipitationThe SSM/I-Based PrecipitationSample for July 2007Sample for July 2007
• Estimates extend into extra-tropics
• Improved quality (e.g. over E. Pacific)
• Noisy caused by limited sampling
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CAL/VAL/Inter-Comparisons CAL/VAL/Inter-Comparisons for better understanding of the products performancefor better understanding of the products performance
• Time• 1991 – 2000(?)
• Scientific Requirements• Understanding quantitative accuracy of the satellite products• Identifying products with better performance
• Technical Developments• Availability of multiple sets of satellite precipitation estimates
• Activities • Proposing / Participating several intercomparison projects
– GPCP Algorithm Intercomparison Project (AIP)– NASA Precipitation Intercomparison Project (PIP)
• Major conclusions
– MERGING of individual information sources is necessary to improve the quality of precipitation analysis
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CMAP CMAP CPC Merged Analysis of PrecipitationCPC Merged Analysis of Precipitation
• Time• 1993 - 1998
• Scientific Requirements• Monitoring and diagnosing climate variability of inter-annual and
intra-seasonal time scales• Verifying reanalyses and climate model simulations
• Technical Developments• Routine production of gauge analysis and satellite estimates• Improved understanding of error structures of input data
• Activities • Developed CPC Merged Analysis of Precipitation
– 2.5olat/lon grid over the entire globe– Monthly / pentad from 1979 to the present– Standard / Real-time versions
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CMAP Global PrecipitationCMAP Global PrecipitationSample for July 2007Sample for July 2007
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Quest for An Extended RecordQuest for An Extended RecordGauge-based Analysis over Global LandGauge-based Analysis over Global Land
• Time• 1998-2002
• Scientific Requirements• Inter-ENSO variability and long-term Variations
• Technical Developments• Availability of improved station data base (GHCN)
• Activities• Developing OI-based PREC (Precipitation Reconstruction)
» Gauge-based analysis over land 0.5olat/lon grid; monthly, 1948 -
» EOF reconstruction over ocean
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Pursuit for high-resolution [1]Pursuit for high-resolution [1]Regional Gauge-Based Analysis over LandRegional Gauge-Based Analysis over Land
• Time• 1996-2004
• Scientific Requirements• Weather-climate linkage • Hydrometeorology (e.g. soil moisture)
• Technical Developments• Availability of daily station archives for several regions• Improved computing / storage capacity
• Activities• Created regional analyses of DAILY precipitation on high-
resolution (0.125o, 0.25o, 0.5o)• Regions include US-MEXICO and Brazil (Higgins and Shi), and
east Asia (Xie et al.)
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Pursuit for high-resolution [2]Pursuit for high-resolution [2]High-Resolution Combined Satellite Estimates over the globeHigh-Resolution Combined Satellite Estimates over the globe
• Time:• 1999-2006
• Scientific Requirements:• Weather-climate linkage / Hydrometeorology / MJO / Tropical
Storm
• Technical Developments:• Real-time high-resolution MW estimates from multiple platforms • Real-time high-resolution IR data over the entire globe• High-performance workstation
• Actions• Developed global full-resolution IR system
• Developed CMORPH (CPC Morphing Technique)– MW estimates interpolated through IR cloud moving vectors– 8kmx8km / 60oS-60oN / 30 min interval from Dec.2002
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CMORPH PrecipitationCMORPH PrecipitationSample CMORPH for 1998Sample CMORPH for 1998
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CPC Unified Precipitation Products [1]CPC Unified Precipitation Products [1]
• Time• 2006
• Scientific Requirements• One single suite of precipitation data sets
serving for most (if not all) applications
• Actions• Started the CPC Unified Precipitation
Products Project
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CPC Unified Precipitation Products [2]CPC Unified Precipitation Products [2]• Overall Goals
• To create a single suite of unified precipitation products for various global / regional applications
• To improve the quantitative accuracy and consistency of the products
• Components• An archive of quality controlled station reports
» Monthly, Daily, Hourly precipitation• A collection of satellite-based precipitation estimates
» Precipitation estimates from individual platforms » Combined satellite estimates (CMORPH)
• A suite of precipitation analyses» Gauge-based, gauge-satellite merged» Monthly, Pentad, Daily, Hourly» Global, Regional » Retrospective, Real-time » State-of-the-art objective techniques
• Short-term Goals
• Gauge-based analysis of daily precipitation over global land• Gauge-satellite merged analysis of daily precipitation over the entire globe
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CPC Unified Precipitation Products [3]CPC Unified Precipitation Products [3]The Global Daily Gauge AnalysisThe Global Daily Gauge Analysis
• >30K station reports
• Enhanced networks over US, Mexico, Brazil, Australia
• GTS elsewhere
• Optimal Interpolation (OI) with orographic correction
(Xie et al. 2007)
• 0.5olat/lon grid over global land
• Daily fields from 1979 to present
• Real-time operations
• Finished development / construction
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CPC Unified Precipitation Products [4]CPC Unified Precipitation Products [4]Gauge Station DistributionGauge Station Distribution
Daily reports from over 30,000 stations worldwide Distributed unevenly with more gauges over US, Brazil, Australia, and
Europe Gauge reports available only from <400 Indian stations through GTS
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CPC Unified Precipitation Products [5]CPC Unified Precipitation Products [5]Example of Daily Gauge Analysis for July 1, 2003Example of Daily Gauge Analysis for July 1, 2003
Major precipitation activities well depicted with reasonable details
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CPC Unified Precipitation Products [6]CPC Unified Precipitation Products [6]Gauge-Satellite Merged Analysis of Global Daily PrecipitationGauge-Satellite Merged Analysis of Global Daily Precipitation
• Combining daily gauge analysis with CMORPH
• Prototype objective algorithm developed to define the
analysis in two steps
• Removing the CMORPH bias through comparison with gauge
• Combining bias-corrected CMORPH with gauge through OI
• Merged analysis consistent with gauge analysis
• 0.25olat/lon grid over the entire globe
• Daily fields from 2000 to the present
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CPC Unified Precipitation Products [7]CPC Unified Precipitation Products [7]Sample gauge and merged analyses for August 2, 2007Sample gauge and merged analyses for August 2, 2007
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CPC Unified Precipitation Products [8]CPC Unified Precipitation Products [8]Sample merged analyses for June, 2008Sample merged analyses for June, 2008
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• JJA Mean for 1998 – 2010
• Spatial pattern of precipitation, especially that associated with topography, well reproduced by the reanalyses
• Larger oceanic precipitation in CFSR and ERA-I
• Weaker precipitation over mid-latitude compared to the CMORPH
• Heavier rainfall over Maritime-continent
Applications [1]Applications [1] Evaluation of Reanalyses JJA Precip.Evaluation of Reanalyses JJA Precip.
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• Standard deviation of 24 hourly means for 1998-2010 (mm/day)
• Diurnal amplitude in CFSR is very similar to that in the observations but presents smaller / larger over ocean, extra-tropical land / tropical land
• Diurnal amplitude in MERRA is generally smaller than that in the observations over tropics and extra-tropics in northern hemisphere and is almost diminished over extra-tropics in southern hemisphere
Applications [2]Applications [2] Precipitation Diurnal CyclePrecipitation Diurnal Cycle
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• Amplitude (mm/day) color shading
• Arrow timing (LST) of maximum hourly precipitation(N=00; E=06; S=12; W=18)
• Spatial pattern of amplitude in association with land / sea contrasts
• CFSR represent minimum amplitude over ocean along coast lines
• Phase in general agreement with observations
Applications [3]Applications [3] Precipitation Diurnal Cycle over MaritimePrecipitation Diurnal Cycle over Maritime
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• Peak in the reanalyses comes earlier
• Amplitude in the reanalyses is larger / smaller over tropical land / ocean
Applications [4]Applications [4] Diurnal Cycle over Four Selected RegionsDiurnal Cycle over Four Selected Regions
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• Longitude section (X-axis) of diurnal evolution (Y-axis) along 40oN over CONUS
• Diurnal cycle (Y-axis) repeated twice
• Precipitation starts from the eastern Rocky around early afternoon (20GMT), traveling eastward and reaching 90oW late afternoon the next day
• Diurnal cycle over land east of 90oW presents fixed phase, opposite to that of precipitation over nearby ocean
• Neither CFSR nor MERRA captures this diurnal variation patterns very well
Applications [5]Applications [5] Diurnal Cycle over CONUSDiurnal Cycle over CONUS
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Comparisons between instantaneous SSS from Aquarius with precipitation averaged over different periods ending at the SSS observation times
Data collected over central Pacific [10oS-10oN; 180o-160oW] In general, SSS decreases with P Better agreement between SSS and P averaged over a longer period
Applications [6]Applications [6] Precipitation and SSS over Central PacificPrecipitation and SSS over Central Pacific
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Applications [7]Applications [7] Driving Hydrological ModelsDriving Hydrological Models
Courtesy of Y.Zhang et al. of OU
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Data Sets AvailableData Sets AvailablePrecipitationPrecipitation
CPC Merged Analysis of Precipitation (CMAP) Monthly / pentad from 1979 to the present 2.5olat/lon over the entire globe
Monthly global gauge analysis (PREC/L) monthly from 1948 to the present 0.5olat/lon over the global land
Daily global gauge analysis (CPC Unified) global land: 0.5olat/lon from 1979 CONUS: 0.125olat/lon from 1948
CMORPH satellite estimates
8km x 8km over the globe from 60oS-60oN 30-min interval from Jan.1, 1998 to the present Satellite-only and bias-corrected versions
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Thanks !Thanks !