The Effect of Cloud Type on Earth's Energy Balance: Results for Selected Regions

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  • 1 Department of Atmospheric Sciences, University of Washington, Seattle, Washington
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Abstract

International Satellite Cloud Climatology Project (ISCCP) Cl cloud information is compared with planetary albedo, outgoing longwave radiation (OLR), and net radiation measured at the top of the atmosphere by the Earth Radiation Budget Experiment (ERBE). Principal component analysis indicates that the day-to-day variations of the abundances of the 35 cloud types of the Cl data are correlated with each other, so that for many purposes the dataset can be well represented by about five cloud types. Using stepwise multiple regression, the ISCCP Cl data can be used to predict the day-to-day variations of the energy balance measured by ERBE for 2.5° regions. Total fractional area coverage of cloudiness is a relatively poor predictor of radiation budget quantities, except in those regions where the cloudiness is dominated by clouds of a single radiative type. If the total fractional area coverage by clouds is divided into contributions from several distinct cloud types, the fractional coverages by these several cloud types will together form a much better prediction of radiation budget quantities than the single variable of total fractional-area cloud coverage. The regression equations can be used to estimate the net effect of clouds on the radiation balance and the contributions from particular types of clouds to albedo, OLR, and net radiation.

Abstract

International Satellite Cloud Climatology Project (ISCCP) Cl cloud information is compared with planetary albedo, outgoing longwave radiation (OLR), and net radiation measured at the top of the atmosphere by the Earth Radiation Budget Experiment (ERBE). Principal component analysis indicates that the day-to-day variations of the abundances of the 35 cloud types of the Cl data are correlated with each other, so that for many purposes the dataset can be well represented by about five cloud types. Using stepwise multiple regression, the ISCCP Cl data can be used to predict the day-to-day variations of the energy balance measured by ERBE for 2.5° regions. Total fractional area coverage of cloudiness is a relatively poor predictor of radiation budget quantities, except in those regions where the cloudiness is dominated by clouds of a single radiative type. If the total fractional area coverage by clouds is divided into contributions from several distinct cloud types, the fractional coverages by these several cloud types will together form a much better prediction of radiation budget quantities than the single variable of total fractional-area cloud coverage. The regression equations can be used to estimate the net effect of clouds on the radiation balance and the contributions from particular types of clouds to albedo, OLR, and net radiation.

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