大尺度环流变化对华北地区夏季水汽输送的影响

Change of Large Scale Circulation and Its Impact on the Water Vapor over North China

利用我国华北地区25个气象站1951—2006年共56年的月降水资料及1948—2006年NCAR/NCEP再分析资料以及NOAA HYSPLIT_4水汽轨迹模型,分析了近50年华北地区夏季降水量、整层水汽输送通量及水汽输送轨迹的变化,并探讨了其影响成因。结果表明,华北夏季水汽输送通量及其轨迹有明显的年际和年代际变化特征;东亚夏季风的南风北界的年际变化对水汽输送有重要影响,南风北界的南撤导致了华北地区水汽输送通量的减少;通过对华北地区降水偏多年和偏少年的比较显示,降水偏多年水汽大部分来自南海,并且输送轨迹较长,水汽主要从西南方向输送到华北,并且偏多年华北上空存在明显的上升运动,偏干年反之。

Using the data of monthly precipitation at 25 stations form 1951 to 2006 in North China and NCAR/NCEP monthly reanalysis data from 1948 to 2006, and the HYSPLIT_4 Model, the variation features of precipitation and the water vapor transportation in North China in summer （JJA） on interdecadal and interannual time scales are investigated. The results show that the characteristic of water vapor transportation and it＇s path change are obvious. The interannual change of northern limit for south wind in summer（June^August） along 100°-125°E （East Asia） has very important influence on the water vapor transportation, the northern limit for south wind moved southward causing the decreasing of the water vapor. The D-value of wind field in more or less precipitation years shows that the southwest windstream of west Pacific subtropical high affects the water vapour transportation over North China in summer; its southwestern air flow from South China Sea carries abundant water vapor to the North China, which brings large quantity of rainfall, and it has obviously rised wind and meridional circulation in averaged along 100°-120° E in North China in typical wet years, which is different in typical dry years.