宁夏春季降水及其典型年份水汽通量特征分析

Character of Spring Precipitation and Water Vapor Flux in Spring-rainy Year and Drought Year in Ningxia

选用1961—2006年宁夏19个主要站降水量分析宁夏春季降水的气候特征,得出其存在16a左右的长周期和8a左右的短周期,但年际、年代际变化特征不明显。宁夏春季降水量与春季首场透雨出现日期存在显著的负相关关系,春季如果出现首场透雨,其降水量对整个春季降水量贡献很大。研究春季降水典型旱涝年850—700hPa水汽通量场的分布,发现影响宁夏春季降水的水汽有两支,一支是来自于孟加拉湾洋面上向东北方向输送的水汽,一支是从里海沿我国新疆地区向东输送的水汽,典型涝年这两支水汽带汇合区域明显向北抬,且汇合区域大,中心值大;典型旱年这两支水汽带汇合区偏西、偏小,中心值也较平均年减小。典型旱涝年水汽通量在u方向差别不大,但在v方向上呈反位向分布,典型涝年宁夏为正距平控制,典型旱年为负距平控制。

According to the precipitation data from 1961 to 2006 of the 19 main stations in Ningxia, the character of the precipitation in spring was analyzed. There were the 16-year long period and the 8-year short period, but the inter-year and the inter-decade changes were not obvious. There was a closely negative correlation between the date of first soaking rainfall and the precipitation in spring, and the possible first soa- king rainfall would make great contribution to the precipitation in whole spring. Research on the water vapor transportation between 850 hPa and 700 hPa in spring-rainy year and drought year shows that there are two vapor inflow corridors to Ningxia. The one comes from the Bengal gulf and the other comes from the Caspian Sea. In the typical spring-rainy year, these two water vapor belts converge in obviously north-oriented region, with large convergence area and big central value. In the typical spring-drought year, these two water vapor belts converge in west-oriented region, with small convergence area and less central value than the normal. The water vapor flux at u direction is not different between the rainy year and the drought year, but adversely different at v direction. The Ningxia area is controlled by positive anomaly in rainy year and controlled by negative anomaly in drought year.