春季东亚副热带西风急流的变化特征及其与中国沙尘天气的关系

利用欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts, ECMWF)提供的ERA-Interim全球大气再分析资料及1980-2012年中国北方逐月沙尘暴发生日数资料, 研究了春季东亚副热带西风急流(70°-120°E)的变化特征及其与中国春季沙尘天气之间的关系。结果表明:1980-2012年春季中国上空急流轴存在北移的趋势, 急流中心略向东移, 急流相对强度随年份增强, 与春季沙尘暴发生总站日数的年际变化呈显著负相关。春季沙尘暴多发年, 东亚副热带西风急流有所减弱, 而在哈萨克斯坦东部、蒙古国、中国内蒙古大部分地区及南疆地区等沙尘源地, 200 hPa纬向风速增大; 500、850 hPa风速、位势高度差值场的分布都有利于中国沙尘源地地面风速增大。在中国沙尘源地, 高层西风风速增大, 动量下传, 引起地面大风, 从而容易产生沙尘暴。

Variation of the East Asian Subtropical Westerly Jet Stream in Spring and Its Relationship with Dust Weather in China

The variation characteristics of the East Asian Subtropical Westerly Jet Stream and its relationship with spring dust weather in China in 1980-2012 is analyzed by using ERA-Interim global atmospheric reanalysis data from the European Centre for Medium-range Weather Forecasts and the standstorm days data in northern China. The results show that the intensity of jet center and the influence scope of the East Asian Subtropical Westerly Jet Stream in winter are much stronger and broader than those in other season, and the center of jet is located in Xinjiang in summer, the position is the most north and west for the whole year, and the intensity is weakest. Overall, the jet axis trends to move northwards in 1980-2012, the center of jet is moving east slightly, the relative intensity of jet increases with years, and it has significantly negative correlation with the sandstorm days value in spring. In the year with more sandstorm days in spring, the East Asian Subtropical Westerly Jet is weaker, but in the source area of dust such as most parts of the eastern Kazakhstan, Mongolia and Inner Mongolia, southern Xinjiang of China, the latitudinal wind speed increases at 200 hPa, and the distribution of difference fields of the wind speed and geopotential height at 500 hPa and 850 hPa is conducive to increase the ground wind speed in the source area of dust. In the source area of dust, westerly wind speed of high-level increases, the momentum transfer to the low-level, which causes the strong wind on the ground, thus easy to produce sandstorm.