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Global Climate Change Digest
A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999

FROM VOLUME 5, NUMBER 1, JANUARY 1992

PROFESSIONAL PUBLICATIONS...
EARTH RADIATION BUDGET

Item #d92jan38

"The Radiative Effects of Clouds and Their Impact on Climate," A. Arking (NASA-Goddard, Greenbelt MD 20771), Bull. Amer. Meteor. Soc., 71(6), 795-813, June 1991.

An overview prepared at the request of the Radiation Commission of IAMAP, examining key results published over the last 15-20 years, along with some unpublished model studies. The annual global mean effect of clouds is generally agreed to cool the climate system, but there is disagreement on magnitude. Observational data are insufficient to adequately determine cloud sensitivity (the differential response of top-of-the-atmosphere fluxes to changes in cloud cover parameters), a critical factor in cloud feedback. Climate simulations indicate clouds may have a strong influence on climate change, but we are far from knowing either the magnitude or the sign of the influence.

Item #d92jan39

"Reflectivities of Uniform and Broken Layered Clouds," J.A. Coakley Jr. (Dept. Atmos. Sci., Oregon State Univ., Corvallis OR 97331), Tellus, 43B(5), 420-433, Nov. 1991.

AVHRR 1 km imagery data from NOAA satellites, collected during the FIRE Marine Stratocumulus Intensive Field Observations, were used to compare reflectivities of the two types of clouds from the same layers. Reflectivities of broken clouds can be estimated by simply reducing the values obtained with plane-parallel theory.

Item #d92jan40

Two items from J. Geophys. Res., 96(D10), Oct. 20, 1991:

"Shortwave, Longwave and Net Cloud-Radiative Forcing as Determined from Nimbus 7 Observations," P.E. Ardanuy (Res.-Data Syst. Corp., Greenbelt MD 20770), L.L. Stowe et al., 18,537-18,549.

The total effect of clouds on the Earth's radiation budget components is evaluated using statistically generated models of cloud forcing that correlate simultaneous satellite observations of cloud properties and radiation budget parameters. Although there is a general compensation over much of the Earth between the warming and cooling effects of clouds, the net effect is cooling, primarily due to effects of clouds over the summer hemisphere oceans.

"Surface Albedo Derived from METEOSAT Imagery with an Application to Africa," G. Nacke (Inst. Meeresknd., Dusternbrooker Weg 20, D-2300 Kiel, Ger.), 18,581-18,601.

Presents a method based on radiative transfer simulations followed by a multivariate analysis. Comparison with in situ data from the Sahara shows good agreement in cases of large, homogeneous surfaces where point measurement represents larger areas.

Item #d92jan41

"A Theoretical and Observational Study of the Radiative Properties of Cirrus: Results from FIRE 1986," P.W. Stackhouse Jr. (Dept. Atmos. Sci., Colorado State Univ., Ft. Collins CO 80523), G.L. Stephens, J. Atmos. Sci., 48(18), 2044-2059, Sep. 15, 1991.

To investigate the sensitivity of cloud radiative properties to altitude, depth and particle size distribution, simulations from a two-stream radiative transfer model were compared with observations. One result is that it may not be possible to use Mie scattering to model the cloud albedo.

Item #d92jan42

"Further Analysis of the Global Outgoing Longwave Radiative Flux Observed by Nimbus," L.H. Auer (Earth-Atmos. Sci., Los Alamos Nat. Lab., Los Alamos NM 87545), C.-Y.J. Kao, J. Geophys. Res., 96(D9), 17,367-17,370, Sep. 20, 1991.

Presents further analysis of a decreasing trend in outgoing longwave radiation (OLR): to demonstrate that the decrease cannot possibly be attributed to a drift in instrument sensitivity; to ascertain that the relative changes in OLR between the two hemispheres are consistent with changes in hemispheric Ts; and to note that a decreasing trend is also found in the insolation data.

Item #d92jan43

"On the Cause of the Relative Greenhouse Strength of Gases such as the Halocarbons," K.P. Shine (Dept. Meteor., Univ. Reading, 2 Earley Gate, Whiteknights, POB 239, Reading RG6 2AU, UK), J. Atmos. Sci., 48(12), 1513-1518, June 15, 1991.

Uses a detailed model of radiative transfer in the thermal infrared to examine some of the reasons for the relative greenhouse strength of gases such as CFCs, which (unlike CO₂) are at relatively low concentrations and therefore close to their optically thin limit. The latter fact implies a relatively large impact as their concentrations increase.

Item #d92jan44

"Global Monitoring of Net Solar Irradiance at the Ocean Surface: Climatological Variability and the 1982-1983 El Niño," B. Chertock (ERL, NOAA, 325 Broadway, Boulder CO 80303), R. Frouin et al., J. Clim., 4(6), 639-650, June 1991.

A new method has been used to generate the first satellite-based long-term climatology of surface solar irradiance over the world oceans, resulting in the first large-scale observation-based examination of cloud solar forcing at the ocean surface. Seasonal and interannual variations are examined.

Item #d92jan45

Two items from J. Geophys. Res., 96(D5), May 20, 1991.

"Scene Identification and Its Effect on Cloud Radiative Forcing in the Arctic," Z. Li (Dept. Meteor., McGill Univ., Montréal, Qué. H3A 2K6, Can.), H.G. Leighton, 9175-9188.

Measurements of cloud radiative forcing in polar regions are less reliable because of difficulty in distinguishing between clouds and ice- or snow-covered surfaces. Comparison of scenes identified by the ERBE algorithm with those deduced from AVHRR radiances showed that they differed both in geotype and cloud cover.

"Differences in Global Data Sets of Atmospheric and Surface Parameters and Their Impact on Outgoing Longwave Radiation and Surface Downward Flux Calculations," M.L.C. Wu (Lab. Atmos., NASA-Goddard, Greenbelt MD 20771), L.A. Chang, 9227-9262.

Studied the effect of clouds on the computation of longwave radiation budget parameters using two sets of cloud fields obtained from two different satellite systems with different retrieval schemes (HIRS2/MSU and ISCCP). Despite differences in global mean coverage, outgoing longwave radiation estimates are very close, but surface downward fluxes differ greatly. Examined the effects of different temperature-humidity fields on budget calculations by using five alternative data sets produced by agencies in the U.S. and Europe.

Item #d92jan46

"Consistency of Earth Radiation Budget Experiment Bidirectional Models and the Observed Anisotropy of Reflected Sunlight," D.G. Baldwin (Dept. Aerospace Eng., Univ. Colorado, Boulder CO 80309), J.A. Coakley Jr., J. Geophys. Res., 96(D3), 5195-5207, Mar. 20, 1991. Assesses the validity of bidirectional models used to estimate radiative fluxes in the Earth Radiation Budget Experiment (ERBE), by comparing model results with the anisotropy directly observed by the ERBE scanner on the Earth Radiation Budget Satellite.

Item #d92jan47

"A Parameterization of Broad Band Radiative Transfer Properties of Water, Ice and Mixed Clouds," B. Rockel (GKSS Forschungszentrum, Inst. Phys., Postfach 1160, D-2054 Geesthacht, Ger.), E. Raschke, B. Weyres, Beitr. Phys. Atmos., 64(1), 1-12, Feb. 1991.

Presents a broad band radiative transfer scheme based on approximate relations derived from exact calculations using Mie theory. For water clouds, 32 different drop size distributions are considered; for ice clouds, a spherical parameterization is compared with one assuming randomly oriented hexagonal ice crystals.

Item #d92jan48

"Deep Optically Thin Cirrus Clouds in the Polar Regions. Part I: Infrared Extinction Characteristics," C. Prabhakara (Code 613, NASA-Goddard, Greenbelt MD 20771), J.-M. Yoo et al., J. Appl. Meteor., 29(12), 1313-1329, Dec. 1990.

Spectral data obtained by the Nimbus satellite in 1970 indicated the existence of optically thin ice clouds in the upper troposphere that probably extended into the lower stratosphere in the polar regions during winter and early spring. Theoretical simulations of infrared spectra in the 8-25 micro m region indicate they have a vertical stratification in particle size.