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Evaluation of the ECHAM family radiation codes performance in the representation of the solar signal

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Publication date 2014
Author Sukhodolov T., Rozanov E., Shapiro A. I., Anet J., Cagnazzo C., Peter T., Schmutz W.,
Project Future and Past Solar Influence on the Terrestrial Climate II
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Original article (peer-reviewed)

Journal GEOSCIENTIFIC MODEL DEVELOPMENT
Volume (Issue) 7(6)
Page(s) 2859 - 2866
Title of proceedings GEOSCIENTIFIC MODEL DEVELOPMENT
DOI 10.5194/gmd-7-2859-2014

Open Access

URL http://www.geosci-model-dev.net/7/2859/2014/
Type of Open Access Website

Abstract

Solar radiation is the main source of energy for 1 Introduction the Earth’s atmosphere and in many respects defines its com- position, photochemistry, temperature profile and dynamics. The magnitude of the solar irradiance variability strongly depends on the wavelength, making difficult its representation in climate models. Due to some deficiencies in the applied radiation codes, several models fail to show a clear response in middle stratospheric heating rates to solar spectral irradi- ance variability; therefore, it is important to evaluate model performance in this respect before doing multiple runs. In this work we evaluate the performance of three generations of ECHAM (4, 5 and 6) solar radiation schemes by a com- parison with the reference high-resolution libRadtran code. We found that all original ECHAM radiation codes miss al- most all solar signals in the heating rates in the mesosphere. In the stratosphere the two-band ECHAM4 code (E4) has an almost negligible radiative response to solar irradiance changes and the six-band ECHAM5 code (E5c) reproduces only about half of the reference signal, while representation in the ECHAM6 code (E6) is better – it misses a maximum of about 15 % in the upper stratosphere. On the basis of the comparison results we suggest necessary improvements to the ECHAM family codes by the inclusion of available pa- rameterizations of the heating rate due to absorption by oxy- gen (O2) and ozone (O3). Improvement is presented for E5c and E6, and both codes, with the introduced parameteriza- tions, represent the heating rate response to the spectral solar irradiance variability simulated with libRadtran much better without a substantial increase in computer time. The sug- gested parameterizations are recommended to be applied in the middle-atmosphere version of the ECHAM-5 and 6 mod- els for the study of the solar irradiance influence on climate.
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