| Through long-time integrations, the ability of NCC/IAP T63 AOGCM to simulate cloud radiative process is analysed in detail. Results show that original model has obvious defects in simulating cloud cover, that is, simulated low cloud cover in eastern ocean and summer hemisphere's ocean from subtropical to mid-latitude is lower remarkably, resulting in too little shortwave radiation absorbed and reflected by atmosphere and excessive outgoing longwave radiation in TOA. Therefore we first modified the cloud cover scheme; because original radiation parameterization scheme is very simple, Fu_Liou radiation parameterization scheme is introduced; aiming at the deficiency in simulating cloud water content, a new diagnostic cloud water scheme is introduced to improve simulation of cloud radiative properties; finally, considering the important role of ice cloud in radiative transfer, we discriminate ice water and liquid water in terms of temperature, and also discuss the model's sensitivity to cloud droplet effective radius. Above modifications make the model's cloud radiative parameterization scheme more reasonable, improve the simulation of cloud radiative process markedly, and also obtain obvious improvement in many aspects of climate simulation. Main results are as follows:(1) The original model shows some ability to simulate distribution of total cloud cover, but simulated low cloud cover in eastern ocean and summer hemisphere's ocean from subtropical to mid-latitude(from latitude 30° to 60°) is lower remarkably. Through modification on cloud cover scheme, simulation of cloud cover in these regions is improved remarkably. Corresponding to improvement on low cloud cover, simulation of cloud radiative forcing is improved markedly, so is net radiation. Modification of cloud cover scheme brings more obvious change to longwave radiation cooling rate than shortwave heating rate. Simulation of atmospheric mean state is improved obviously in many aspects, especially temperature, geopotential, vertical velocity in tropic, and specific humidity etc. simulation error in SST is obvious: except some coastal regions and between 30°S and 60°, SST's simulation is generally lower. Modification of cloud cover scheme doesn't bring consistent improvement on SST. Ocean current's change is characterized by enhancement of equatorial current and equatorial counter current, therein the latter results in SST's rising in eastern equatorial ocean where SST is lower originally. Furthermore, cloud cover's change makes SST's seasonal cycle more reasonable in eastern equatorial ocean.(2) In original radiation parameterization scheme(Morcrette scheme), treatment of cloud cover in radiation calculation is very simple, and division of radiative bands is too coarse. Therefore Fu_Liou scheme is introduced which adopts binary cloud, finer bands division and more accurate four-stream approximation.Comparing two schemes we find: Fu_Liou scheme has more reasonable treatment of TO A incoming shortwave radiation than Morcrette scheme; Fu_Liou scheme brings obvious improvement to convective motion in tropic region, which leads to improvement on high cloud simulation; due to adoption of binary cloud, cloud shortwave absorption simulated by Fu_Liou scheme enhances compared to Morcrette scheme,even though simulated total cloud cover decreases. In middle and low latitudes, planetary albedo simulated by Fu_Liou scheme is closer to ERBE observation.(3) Origional cloud water scheme uses saturated specific humidity to diagnose cloud water content, which results in obvious simulation error in middle and high latitudes. So we introduce a new diagnostic scheme using precipitable water to parameterize cloud water content. Results show that introduction of new scheme improves simulation of cloud water content in the vicinity of latitude 60° remarkably, but there is still obvious error in middle and low latitudes compared to ERA data. New scheme enhances cloud shortwave absorption in middle and high latitudes of summer hemisphere, and also enhances reflection of shortwave rad...
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