An assessment of data products for studies of clouds and radiation

(INVITED)

Ehrhard RaschkeUniversity of Hamburg, Germany

William R. Rossow, Yuan-Chong ZhangNASA, GISS & Columbia University, New York NY

Paul W. StackhouseNASA, LaRC Hampton VA

(With contributions by B. Carlson, M. Giorgetta, S. Kinne, M. Wild, R. Cess, G. Potter)

5th GEWEX Science Conference, 20 – 24 June 2005

Orange County, California

IPCC 2001

Clouds: -50 to +35 Wm-2

ABC !

See also GCOS papers

CLOUDS

Surface Observations,

RAWIN-Sondes,

(Neph-Analyses, photographic averages)

TOVS, ISCCP, HIRS/2, SAGE, POLDER, and many others

To contrast clouds against background of passive measurements: Correlative data sets on state of atmosphere and ground are needed.

Stubenrauch (2005)

Cloud amount 69/46

Cloud top pressure 588/596

Top minus surface temperature –26/-27

ISCCP vs. TOVS

Summary for clouds:

1. There are now several data sets available for geometric and radiometric cloud field properties and for occurrence of clouds covering more than 15 years with largest uncertainties over Polar Regions.

2. There are further numerous results available for microphysical cloud field properties covering shorter periods.

CONCLUSIONS:

1. The cloud products are not necessarily compatible due to different techniques of measurements and analyses and sampling.

2. GEWEX must develop and accept an appropriate terminology on cloud characteristics.

3. Significant improvements expected when “A-Train data” is included.

RADIATION PRODUCTS

Studies of Earth’s Radiation Climatology began in late 19th century.

-.-.-.-.-

At Top of Atmosphere (TOA) with satellite data since ~1960

Now: ERBE, CERES, ScaRaB, GERB (and ISCCP, SRB, others)

At Ground with satellite information since ~1975;

Now: ISCCP, GEWEX-SRB, + various shorter time series over regions.

Radiation product

 

Primarily sensitive to … (in some order of priority)

Insolation at TOA TSI, Astro-mechanics, spectrum, cut-off angle

Planetary albedo Clouds, surface albedo, aerosols, scene identification, angular models

Outgoing longwave radiation at TOA

Temperature of atmosphere and surface, water vapor, clouds, scene, angular models

Downward longwave at surface Atmospheric temperature and water vapor, clouds

Upward longwaveat surface

Surface skin temperature and effective emittance

Downward solar radiation at surface Clouds, aerosols, moisture; insolation at TOA

Upward solar radiation at surface Downward solar, surface albedo (and spectrum)

Longwave budgets at TOA and surface; integral divergence

(Temperatures at surface and in the atmosphere; clouds)

Solar budgets at TOA and surface; integral divergence

(Clouds, aerosols, surface albedo)

1991 - 1995

Planetary radiation budget

1991 to 1995

Validation:

Solar (left) and terrestrial (right)

at TOA:

CERES vs. ISCCP

(B.Carlson, GISS)

0,94

0,96

0,98

1

1,02

1,04

1,06

1,08

1,1

1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

75-90S 60-75S 30-60S 00-30S 00-30N 30-60N 60-75N 75-90N

OLR - Ratio: ISCCP/SRB

-5

5

15

25

35

1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

75-90S 60-75S 30-60S 00-30S 00-30N 30-60N 60-75N 75-90N

Incident solar radiation at TOA (ISCCP

minus SRB) Wm-2

> 45

AMIP-2, mean incoming solar radiation at TOA in May and November (1985-1988)(with R. Cess, S. Kinne, M. Giorgetta, M. Wild)

DJF

TSI PMOD-composite 2005

AMIP-2: Deviations monthly (1985-88) insolation at TOA from their zonally averages

BSRN vs. ISCCPMartin Wild, ETHZ

Downward solar Downward atmospheric

1991 - 1995

Total radiative flux divergence

1991 to 1995

Summary for Radiation Products(from models, satellite data and computations with climate data)

1. At TOA: ALL (!!) radiation climatologies must use “same solar forcing”. Upward fluxes and CE-s need thorough validation vs. CERES and other space-based measurements.

2. At surface: Atmospheric transmittance and emittance: ISCCP > SRB; surface albedo and emission seasonally different; cloud effects: need comparison between measured and computed ! Use network data !

3. Radiative flux divergence: Uncertainties are dominated by errors in the net budgets at both boundaries.

-.-.-.-.-

There is an urgent need to establish and accept scale dependent uncertainty and stability criteria for cloud and radiation products and data sets must be characterized accordingly. The next workshop should develop mechanisms for a steady quality control (also for correlative data).

Thanks to all contributors to

the data sets

E.R. enjoyed excellent hospitability in Sapporo, and at CCSR and at NIPR in Tokyo.

GEWEX: develop and apply quality control procedures