Cirrus cloud horizontal and vertical inhomogeneity effects in a GCM |
| |
Authors: | Yu Gu K N Liou |
| |
Institution: | (1) Department of Atmospheric Sciences, University of California, Los Angeles, CA, USA |
| |
Abstract: | Summary A set of the inhomogeneity factor for high-level clouds derived from the ISCCP D1 dataset averaged over a five-year period
has been incorporated in the UCLA atmospheric GCM to investigate the effect of cirrus cloud inhomogeneity on climate simulation.
The inclusion of this inhomogeneous factor improves the global mean planetary albedo by about 4% simulated from the model.
It also produces changes in solar fluxes and OLRs associated with changes in cloud fields, revealing that the cloud inhomogeneity
not only affects cloud albedo directly, but also modifies cloud and radiation fields. The corresponding difference in the
geographic distribution of precipitation is as large as 7 mm day−1. Using the climatology cloud inhomogeneity factor also produces a warmer troposphere related to changes in the cloudiness
and the corresponding radiative heating, which, to some extent, corrects the cold bias in the UCLA AGCM. The region around
14 km, however, is cooler associated with increase in the reflected solar flux that leads to a warmer region above. An interactive
parameterization for mean effective ice crystal size based on ice water content and temperature has also been developed and
incorporated in the UCLA AGCM. The inclusion of the new parameterization produces substantial differences in the zonal mean
temperature and the geographic distribution of precipitation, radiative fluxes, and cloud cover with respect to the control
run. The vertical distribution of ice crystal size appears to be an important factor controlling the radiative heating rate
and the consequence of circulation patterns, and hence must be included in the cloud-radiation parameterization in climate
models to account for realistic cloud processes in the atmosphere. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|