知识与财富的链接
利用历史天气图和NCEP再分析资料,普查了1980～2002年出现在华北平原地区的回流天气过程.依据500 hPa环流形势,对华北平原的回流天气形势分为两种:两槽一脊型和高纬低压带型.针对不同的天气分型对产生回流天气的动力条件、水汽来源进行了合成诊断分析.结果表明:涡度和散度的垂直分布与一般的降水过程不同,低层存在辐散和反气旋环流;自东北南下经渤海回流到华北平原的空气是比较干的.该文分析结果有助于预报业务人员了解回流天气,提高华北回流天气的预报准确率.
By using the NCEP/NCAR monthly mean reanalysis data from 1948 to 1999,the characteristic indexes are defined to describe the Mascarene High (MH), based on the evolution characteristics of the climatological geopotential height and streamline fields at 850 hPa. By calculating the indexes, the features of the MH variations on different time scales are examined. The results show that the seasonal variations of MH were remarkable: it was the strongest and the location is more westward and northward in southern winter, and vice versa in southern summer. The anomaly variations of MH are also studied. It is shown that MH had the obvious interannual and interdecadal variations. On the interdecadal time scale, the area and center intensity of MH increased gradually, and the center location moved eastward and southward slowly in 52 years.
