天津地区雨季降水异常的前期强影响信号研究

Investigations on the Precedent Strong Influence Signal for the Anomalous Precipitation in Rainy Season over Tianjin Area

利用1958—2007年天津地区4站月降水资料以及NCEP/NCAR月平均再分析数据资料集,采用相关分析和合成分析,研究了天津地区雨季降水异常的前期强影响信号。结果表明:天津地区雨季降水量在很大程度上决定了全年的降水量,雨季降水存在显著的年际变化和一定的年代际变化。天津地区雨季降水与前期冬季2月NAO存在显著的反相关关系,前期冬季2月异常的NAO可能是天津地区雨季降水异常的前期强影响信号。NAO偏弱年,天津地区上游有强低值系统发展,南亚高压、高空副热带西风急流和热带东风急流位置偏北,阿拉伯海到孟加拉湾一带有季风低压和季风槽发展。上述系统的配置有利于天津地区雨季降水偏多。NAO偏强年上述情况则相反。

Based on the 1958-2007 monthly precipitation data at 4 stations over Tianjin area and the NCEP/NCAR reanalysis data set,the precedent strong influence signal for the anomalous precipitation in rainy season over Tianjin area is investigated by employing the simple correlation and composite analysis. The results show that the annual precipitation over Tianjin area is mainly concentrated in the rainy season. There exists pronounced interannual variability and certain interdecadal variations about the rainfall in rainy season.Additionally,there is a significant negative correlation between the precipitation and NAO in the preceding February.The anomalous NAO in the preceding February has a good potential to be the precedent strong influence signal for the abnormal precipitation over Tianjin area.In the years of weak NAO.the low value systems develop on Tianjin upstream,the South Asia high,the subtropical upper westerly jet and the tropical upper easterly jet lie more northward,and the developments of monsoon depression and trough are noticeable from the Arabian Sea to the Bay of Bengal.The rainfall is likely to be more than normal due to the distribution of the above mentioned synoptic systems.The situations are just opposite in the years of strong NAO.