A RADIATION SCHEME FOR CIRCULATION AND CLIMATE MODELS

Abstract

A versatile radiation scheme is developed to calculate radiative fluxes and heating rates for the solar and infrared emission spectrum to be employed in circulation and climate models. This scheme incorporates the effects of atmospheric water vapor, carbon dioxide, ozone, pollution gases, aerosol particles and multi-layered clouds of arbitrary cloud cover. Multiple scattering is handled with an improved flux method in the solar spectrum and the atmospheric window region. An extended emissivity method is used to treat the remaining infrared spectrum taking account of all overlapping effects and of grey clouds. The method is tested with success on the basis of measurements in the solar and infrared emission spectrum. It is found that in the lower 10 km of a tropical cloudless atmosphere both calculated and measured infrared cooling rates vary from -3.5 to -1.5 K/d as function of height. In the upper part of a midlatitude low cloud the measured infrared cooling rate of -5 K/h was duplicated with high precision by the model. Solar heating rates in the polluted midlatitude urban atmosphere may exceed 13 K/d verifying recent measurements under similar conditions.