East Asia and Western Pacific METEOROLOGY AND CLIMATE

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space. This effect is the green-house effect of clouds and is termed as the longwave
cloud forcing; clouds are also shown to reflect more shortwave radiation compared
to clear sky. This enhancement of reflection is referred to as the shortwave cloud
forcing. The net effect of cloud to earth-atmosphere system is the sum of longwave/shortwave
cloud forcing and is referred to as cloud radiative forcing. In
view of recent estimate of the cloud-radiative-effect as pointed out Ramanathan
et al. (1989), the global annual mean budget is further decomposed to identify
the cloud-radiative-effect in the model atmosphere. Fig. 4 indicates some budget
terms in the clear and cloudy atmosphere. Planetary albedo of 59.6% (16.6%)
in cloudy (clear) atmosphere is clearly shown, along with the surface shortwave
absorption of 28.3% (69.6%). The difference for the cloud/clear atmosphere for
the surface shortwave absorption is 41.3%, which is quite large. The atmospheric
absorption of shortwave radiation in cloud (clear) atmosphere is 12.1% (13.8%).
The outgoing surface longwave radiation in clear atmosphere is larger than the
cloudy atmosphere by 15.8% (the difference of 28.3% and 12.5%). So the cloudradiative-effect
to the earth-atmosphere system is mainly in the large reflection of
the shortwave fluxes and the modification of the outgoing longwave fluxes. The
change in absorption of shortwave is relatively small. Prom Ramanathan et al.
(1989), their estimate of the net cloud-radiative-effect is a cooling effect, on the
order of -14 to -21 w/ra 2 . In our estimate as illustrated in Figs. 1 and 4, this effect
realized by the present model is around .-35 w/ra 2 (10.9% of the total incoming
solar radiation). Although the quantity is larger that the observed estimate, the
simulated model cloud kept the consistent physical reasoning as observed.
Seasonal characteristics for the global mean is presented in Fig. 5. The
planetary albedo is larger in January than July. The atmospheric absorption of
shortwave radiation does not experience much seasonal variation.
3.2 Regional characteristics
The simulated global structure of the radiation budget indicated overestimation
of the planetary albedo, which may be due to the model's overestimation of
the cloudiness. The simulated atmospheric shortwave absorption and longwave
cooling were consequently reduced. Bear this characteristics in mind, the simulated
regional radiative balance will be presented here.
The whole globe is divided into five regions, those are 30*JV-30°S, 30°^-
60° JV, 30 0 5-60°5, 60°JV"-90°JV, 60*5-90*5. The radiative structure for the region
3Q 0 JV-3Q°S in January and July is presented in Fig. 6. The seasonal variation