亚洲地区云量参数化的对比试验及云的影响

COMPARISON TESTS OF PARAMETERIZATION SCHEMES FOR CLOUD COVER OVER ASIA AND THE EFFECT OF CLOUD COVER

本文首先分析了亚洲地区气候云量及相对湿度的分布事实。然后,利用一有限区域模式,1979年FGGE资料和我们综合的实测云量资料等,对选用或修改了的6种云量诊断方案,就1979年冬、春及夏季的4次个例进行了对比试验。最后还针对四川‘81.7’特大暴雨个例,按有无云两种方案,作了48小时预报试验。结果表明,在6种云量诊断方案中,以考虑了亚洲地区特点的ECMWF修正方案和气候云量修正方案对云区及云量的诊断效果最好。另外,云的影响对大范围短期预报虽不重要;但可对局部地区的短期天气变化有一定影响。即模式云量增加后对流层中低层温度升高,抑制陆上对流发展,预报的降水量减少。

In this paper, first, the facts of the temporal and space distributions for climatic cloud cover and the vertical profiles of relative humidity over Asia were analysed. Then, the comparison tests of six sets of diagnostic schemes for cloud amount were carried out for four cases in 1979 covering Winter, Spring, and Summer, utilizing a six-level limited area model with complex terrain and model physics processes, the FGGE data of 1979, and the observed cloud cover data combined by ourselves. Finally, a sensitive test of effect of cloud amount on short range weather prediction was conducted.The results show:1) there are obvious temporal-and space-variations of cloud cover over Asia. The characteristics of cloud cover and relative humidity over Asia are something different from those over Atlantic.2) Among above six schemes both the modified ECMWF and modified climate cloud ones taken cloud characteristics of Asia into account have the best performance for the diagnoses of high-and lower-cloud areas and cover, especially for high-cloud.3) The changes in cloud amount have no significant influence on the short range prediction over large area, but may have a certain influences on the prediction over a particular local region, i. e., with the increase in cloud amount, the temperature in mid-and lower-troposphere gets warmer, the precipitation light.