秦岭南北区域夏季极端降水与西太平洋副热带高压的关系

利用1960—2016年秦岭南北地区47个站点的逐日降水数据与同期西太平洋副热带高压的面积指数、强度指数、西伸脊点、脊线位置数据,统计分析了秦岭南北地区夏季极端降水指数与副高指数的相关关系。结果表明:①从整体上看,各极端降水指数与面积指数、强度指数总体成正相关;与西伸脊点总体上成负相关,但会出现一些异常年份和负相关年份;而各极端降水指数与脊线位置的关系呈现正负相关交替的现象。年代际分析和M-K检验表明,副高指数、极端降水指数在20世纪80年代发生了增强、增大的突变。②把秦岭南北划分为4个区域后,无论时间上还是空间上,当面积指数、强度指数偏大,脊线位置偏南,西伸脊点偏西,秦岭以北、秦岭以南和汉水流域中部趋于干旱,汉水流域东西部和巴巫谷地极端降水偏多;反之,相反。这样的极端降水格局应是秦岭等山脉对副高在气候上的响应结果。③秦岭南北地区夏季极端降水偏多年与面积指数偏大、强度指数偏强、脊线位置偏南、西伸脊点偏西相联系,反之,相反。副高西伸可能是秦岭南北地区极端降水增大的重要原因之一。

Relationship between the Summer Extreme Precipitation in the South and North of the Qinling Mountains and the Western Pacific Subtropical High

The relationship between the summer extreme precipitation in the north and south of the Qinling Mountains and the western pacific subtropical high was analyzed based on the daily precipitation data from 47 stations in the north and south of the Qinling Mountains and the data of area, intensity, west ridge point and ridge line index of western pacific subtropical high from 1960 to 2016. The results showed that: ①On the whole, the extreme precipitation indices were positively correlated with the area and intensity of western pacific subtropical high; they were negatively correlated with the west ridge point, but some abnormal years and negatively-correlated years appeared. The positive and negative correlations between the extreme precipitation indices and the ridge line occurred alternatively. Decadal analysis and M-K test revealed that a mutation increase of the western subtropical high indices and the extreme precipitation indices occurred in the 1980s; ②After the north and south of the Qinling Mountains were divided into four regions, no matter temporally or spatially, drought occurred in the regions to the north and to the south of the Qinling Mountains and the central Hanshui River Basin, but the frequency of extreme precipitation increased in the east and west parts of the Hanshui River Basin and the Bawu Valley when the area and intensity indices were larger, the ridge line index was more southward, and the west ridge point index was more westward. On the contrary, it was opposite. Such extreme precipitation patterns should be the result of response of the Qinling Mountains to the subtropical high; ③The increase of summer extreme precipitation in the north and south of the Qinling Mountains in some years was related to the higher area index, intensity index, southward ridge line and westward ridge point. On the contrary, it was opposite. The westward pacific subtropical high may be one of the important reasons for the increase of extreme precipitation in the north and south of the Qinling Mountains.