Numerical studies of the role of clouds in the present climate.

摘要

Until recently there has been lingering skepticism, in the general circulation modeling community, that the radiative effects of clouds significantly influence the atmospheric general circulation. Zonally uniform ''observed'' cloud amounts were, in some cases, prescribed by modelers who preferred to avoid confronting the complex physics of cloud formation. Ironically, GCMs have provided the proof that the radiative effects of clouds are important for the general circulation of the atmosphere. An important concept in analysis of the effects of clouds on climate is the cloud radiative forcing, which is defined as the difference between the radiative flux which actually occurs in the presence of clouds, and that which would occur if the clouds were removed but the atmospheric state were otherwise unchanged. We also use the term CRF to denote warming or cooling tendencies due to cloud-radiation interactions. Cloud feedback is the change in CRF that accompanies a climate change. It is useful to distinguish among three aspects of the CRF: the ''planetary CRF'' acting at the top of the atmosphere, the ''surface CRF'' at the Earth's surface, and the ''atmospheric CRF,'' which acts on the atmospheric itself and is the difference between the planetary and surface CRFs. This paper reviews the magnitudes, distribution causes, and consequences of the CRF, as they relate to climate modeling. A review of some earlier studies is combined with a brief presentation of new, previously unpublished results. 15 refs., 6 figs.