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Comparison of the tropical radiative flux and cloud radiative effect profiles...

Su, W., A. Bodas-Salcedo, K. Xu, and T. Charlock (2010), Comparison of the tropical radiative flux and cloud radiative effect profiles in a climate model with Clouds and the Earth’s Radiant Energy System (CERES) data, J. Geophys. Res., 115, D01105, doi:10.1029/2009JD012490.

An insightful link of model performance to the physical assumptions in general circulation models (GCMs) can be explored if assessment of radiative fluxes and cloud radiative effects go beyond those at the top of the atmosphere (TOA). In this study, we compare the radiative flux profiles (at surface, 500 hPa, 200 hPa, 70 hPa, and TOA) and cloud effect profiles (500 hPa, 200 hPa, and TOA) from HadGAM1, using Surface and Atmospheric Radiation Budget (SARB) data from Clouds and the Earth’s Radiant Energy System (CERES) on the TRMM satellite over the tropics (30°S–30°N). Comparison at TOA reveals that HadGAM1 agrees well with CERES for mean cloud height but lacks in cloudiness. Comparing to its predecessor, HadAM3, HadGAM1 agrees better with observations in TOA LW cloud effects, net cloud effects, and the ratio of SW to LW cloud effects. Extending the comparison to multiple levels, we gain additional insight into the vertical differences in clouds: for clouds at heights below 500 hPa, HadGAM1 and CERES are in good agreement in terms of cloudiness, but HadGAM1 underestimates the average cloud height; for clouds between 500 and 200 hPa, HadGAM1 underestimates the cloudiness but overestimates the average cloud height; for clouds at heights above 200 hPa, HadGAM1 produces more clouds than in CERES. Stratifying the cloud effects by dynamic regimes, we find that HadGAM1 underestimates cloudiness and overestimates averaged cloud height in the convective regimes, but the opposite is true in the strong subsidence regimes.

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Modeling Analysis and Prediction Program (MAP)