长江流域典型旱/涝夏季大气中的水汽输送

ANALYSES OF WATER VAPOR TRANSFER CHARACTERISTICS OVER CHINA IN TYPICAL DROUGHT/FLOOD SUMMER IN THE YANGTZE RIVER VALLEY

1980年夏季(6、7、8月),雨带在30-33°N间南北摆动,长江流域暴雨频繁,造成严重涝灾。1985年夏季长江流域以局部阵性降水为主,雨带不明显,是典型的夏旱年。本文在(20—45°N,100—125°E)范围内选取72个测站,利用每日00Z探空资料计算这两年6、7、8三个月从地面到100hPa各层和整层的水汽总输送、平均输送和涡旋输送,得出:80和85年夏季我国大气中水汽输送有明显不同的特征,大范围内水汽通量的分布与降水量的分布和降水特点相一致,与西太平洋副热带高压系统和西风带气流的强弱有密切的关系;80年夏季水汽输送量大,涡旋输送由南向北一直输送到黄河流域以北,850hPa上长江中下游有明显的水汽辐合,华南地区有明显的冰汽辐散;85年夏季水汽输送量小,经向输送弱,涡旋输送无明显一致的输送方向,850hPa上长江流域处于水汽辐散或弱辐合区中。分析100—115°E间一些测站水汽经向输送振荡的方差谱,得出在80年夏季长江流域地区对流层中下层有较明显的7—8天振荡,85年夏季则有很强的30天左右的振荡。

In this paper, the summers ( June-August ) of 1980 and 1985 are selected as typical flood and drought ones in the Yangtze Liver ValleyCYRV). The total, average and eddy fluxes of water va or transfer(WVT )in the months of the summers arc com uted by using the data from 72 stations. The results are as fo llows: ( 1 ) The char teristies of WVT over China were different between the summers of 1989 and 1935. The distributions of WVT matched well with the distributioas of the rainfall and the characteristics of the precipitations in the summer months of 1980 and 1985 and were related intimately to the subtropical Pacific High and the westerly current of westerlies: ( 2 )In the summer of 1980, the values of WVT were large and the eddy WVT were mainly from southern China to northern China. On the 850hPa , the convergence of WVT over the middle and lower reaches of VRV and the divergence of WVT in southern China were evident. The meridional WVT with 7-8-day oscillation was evident in the lower layer of troposphere over YRV; (3 )In the summer of 1985, the values of WVT were much smaller than that in 19SO. The directions of the eddy WVT were not in order. On the 850hPa, YRV was in the divergence or partly in weak convergence. The 30-day oscillation of meridional WVT was very significant over YRV.