一个海气耦合模式模拟的云辐射过程

CLOUD AND RADIATION PROCESSES SIMULATED BY A COUPLED ATMOSPHERE-OCEAN MODEL

利用NCC/IAP T63海气耦合模式进行了20 a积分,详细分析了模式对云量及其辐射影响的模拟能力。结果表明,模式能够模拟出云量分布的基本特征,但同ISCCP卫星观测资料及ERA再分析资料相比还存在较大的差距,总体表现为模拟的云量偏小,尤其是海洋上部分地区出现了异常的低值区。通过对云量方案的改进,明显改善了两大洋东岸、夏半球副热带到中纬度海洋上空低云的模拟。但模式对热带印度洋到西太平洋地区云量的模拟仍然存在明显的偏差,这主要是由于模式对该地区强对流云模拟能力差,造成该地区高云模拟存在较大的误差。对辐射及其云辐射强迫的分析表明,模式对长波及其云辐射强迫的模拟要明显好于短波。短波辐射模拟的偏差主要是由于短波云辐射强迫模拟过小、耦合模式对积雪和海冰模拟较差、以及未考虑气溶胶的影响等原因共同引起的;而长波辐射模拟的差距主要是云量以及下垫面温度模拟不足造成的。相应于云量方案的改进,两大洋东岸、夏半球副热带到中纬度海洋上辐射(尤其是短波辐射)的模拟有了明显的改善,这也明显改进了这些地区的净辐射模拟。

Using NCC/IAP T63 atmosphere-ocean coupled model, a 20 years＇ integration was processed, and its capability to simulating cloud and radiation was also analyzed in detail, The results show that the model can simulate the basic distribution of cloud cover, however obvious differences still exist compared to ISCCP satellite data and ERA reanalysis data. The simulated cloud cover is less in general, especially the abnormal low values in some regions of ocean. By improving the cloud cover scheme, simulated cloud cover in eastern ocean, summer hemisphere＇s ocean from subtropical to mid-latitude is considerably improved. But in tropical Indian Ocean and west Pacific the cloud cover difference is still evident, which is mainly caused by the deficiency of high cloud simulation in these regions caused by deep cumulus convection. In terms of the analysis to radiation and cloud radiative forcing, it was found that simulation on long wave radiation is better than short wave. The simulation error of short wave radiation is caused mostly by the simulation difference in short wave radiative forcing, sea ice and snow cover, and also by not involving aerosol＇s effect. The simulation error of long wave radiation is mainly resulted from deficiency in simulating cloud cover and underlying surface temperature. Corresponding to improvement of cloud cover, simulated radiation（especially short waye radiation） in eastern ocean, summer hemisphere＇s ocean from subtropical to mid-latitude is remarkably improved. This also brings obvious improvement to net radiation in these regions.