Cloud radiative forcing of subtropical low level clouds in global models |
| |
Authors: | Johannes Karlsson Gunilla Svensson Henning Rodhe |
| |
Institution: | (1) Department of Meteorology, Stockholm University, Stockholm, Sweden |
| |
Abstract: | Simulations of subtropical marine low clouds and their radiative properties by nine coupled ocean-atmosphere climate models
participating in the fourth assesment report (AR4) of the intergovernmental panel on climate change (IPCC) are analyzed. Satellite
observations of cloudiness and radiative fluxes at the top of the atmosphere (TOA) are utilized for comparison. The analysis
is confined to the marine subtropics in an attempt to isolate low cloudiness from tropical convective systems. All analyzed
models have a negative bias in the low cloud fraction (model mean bias of −15%). On the other hand, the models show an excess
of cloud radiative cooling in the region (model mean excess of 13 W m−2). The latter bias is shown to mainly originate from too much shortwave reflection by the models clouds rather than biases
in the clear-sky fluxes. These results confirm earlier studies, thus no major progress in simulating the marine subtropical
clouds is noted. As a consequence of the combination of these two biases, this study suggests that all investigated models
are likely to overestimate the radiative response to changes in low level subtropical cloudiness. |
| |
Keywords: | Low clouds Cloud radiative forcing Global climate models Stratocumulus Cloud feedback ERBE ISCCP IPCC |
本文献已被 SpringerLink 等数据库收录! |