Observed Screen (Air) and GCM Surface/Screen Temperatures: Implications for Outgoing Longwave Fluxes at the Surface

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Abstract
There is direct evidence that excess net radiation calculated in general circulation models at continental surfaces [of about 11–17 W m−2 (20%–27%) on an annual basis is not only due to overestimates in annual incoming shortwave fluxes [of 9–18 W m−2 (6%–9%)], but also to underestimates in outgoing longwave fluxes. The bias in the outgoing longwave flux is deduced from a comparison of screen-air temperature observations, available as a global climatology of mean monthly values, and model-calculated surface and screen-air temperatures. An underestimate in the screen temperature computed in general circulation models over continents, of about 3 K on an annual basis, implies an underestimate in the outgoing longwave flux, averaged in six models under study, of 11–15 W m−2 (3%–4%). For a set of 22 inland stations studied previously, the residual bias on an annual basis (the residual is the net radiation minus incoming shortwave plus outgoing longwave) varies between 18 and −23 W m−2 for the models co... Abstract There is direct evidence that excess net radiation calculated in general circulation models at continental surfaces [of about 11–17 W m−2 (20%–27%) on an annual basis is not only due to overestimates in annual incoming shortwave fluxes [of 9–18 W m−2 (6%–9%)], but also to underestimates in outgoing longwave fluxes. The bias in the outgoing longwave flux is deduced from a comparison of screen-air temperature observations, available as a global climatology of mean monthly values, and model-calculated surface and screen-air temperatures. An underestimate in the screen temperature computed in general circulation models over continents, of about 3 K on an annual basis, implies an underestimate in the outgoing longwave flux, averaged in six models under study, of 11–15 W m−2 (3%–4%). For a set of 22 inland stations studied previously, the residual bias on an annual basis (the residual is the net radiation minus incoming shortwave plus outgoing longwave) varies between 18 and −23 W m−2 for the models co...

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