Radiative Transfer Within the Earth's Troposphere and Stratosphere: A Simplified Radiative-Convective Model

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  • 1 NASA Langley Research Center, Hampton, Va. 23665
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Abstract

A simplified radiative transfer model for the earth's atmosphere is presented. The simplification is achieved by a combination of band absorptance and emissivity formulation for treating radiative transfer due to H2O, CO2 and O3. The model incorporates the major and minor radiative transfer processes due to H2O, CO2 and O3. The radiative model is used to develop an efficient and accurate radiative-convective model. Results for the global surface temperature, stratospheric thermal structure, and the net outgoing longwave flux are presented.

The computed thermal structure of the stratosphere and the stratospheric cooling rates are in excellent agreement with previous studies. The amplitude of the diurnal temperature difference in the upper stratosphere obtained from the present model is larger by about 50% than Leovy's (1964) results. This difference is due to the inclusion of Doppler broadening effects and CO2 hot and minor isotopic bands in the present model.

The flux calculations indicate that the relatively minor bands like the CO2 hot and minor isotopic bands and the e-type absorption by the H2O continuum band have to be included in order to compute the outgoing flux F to within 1% accuracy. Results are also presented for the sensitivity of F to surface temperature. It is shown that the H2O e-type absorption has a substantial influence on the sensitivity parameter dF/dTs.

Abstract

A simplified radiative transfer model for the earth's atmosphere is presented. The simplification is achieved by a combination of band absorptance and emissivity formulation for treating radiative transfer due to H2O, CO2 and O3. The model incorporates the major and minor radiative transfer processes due to H2O, CO2 and O3. The radiative model is used to develop an efficient and accurate radiative-convective model. Results for the global surface temperature, stratospheric thermal structure, and the net outgoing longwave flux are presented.

The computed thermal structure of the stratosphere and the stratospheric cooling rates are in excellent agreement with previous studies. The amplitude of the diurnal temperature difference in the upper stratosphere obtained from the present model is larger by about 50% than Leovy's (1964) results. This difference is due to the inclusion of Doppler broadening effects and CO2 hot and minor isotopic bands in the present model.

The flux calculations indicate that the relatively minor bands like the CO2 hot and minor isotopic bands and the e-type absorption by the H2O continuum band have to be included in order to compute the outgoing flux F to within 1% accuracy. Results are also presented for the sensitivity of F to surface temperature. It is shown that the H2O e-type absorption has a substantial influence on the sensitivity parameter dF/dTs.

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