春季塔里木河流域浮尘天气与副热带西风急流的联系

Relations of the Float Dust over the Tarim River Basin and the Subtropical Westerly Jet Stream in Spring

摘要:

利用NCEP(National Centers for Environmental Prediction)大气再分析资料和1988-2021年塔里木河流域气象站浮尘逐月发生日数资料，研究了春季副热带西风急流（20°～40°N，70°～95°E）的变化特征与该流域浮尘天气之间的关系。结果表明:春季该急流轴存在北移的趋势，急流强度随年份增加而减弱，春季急流轴南北移动与流域浮尘频数的年际变化呈显著负相关。与少发年相比较，春季该流域浮尘多发年西风急流向南移动，200 hPa西风急流北侧的纬向风速增大较多，尤其在塔河流域上空，风速增大较明显， 500 hPa和850 hPa风速和位势高度的分布都有利于该流域地面风速增大。对流层高层西风风速增大，动量下传，引起塔里木河流域地面风速增大，导致容易发生浮尘天气。

Abstract:

Using NCEP (National Centers for Environmental Prediction) atmospheric reanalysis data and the monthly occurrence records of floating dust days in the Tarim River Basin from 1988 to 2021, this research investigates the variation characteristics of the subtropical westerly jet stream (20°-40°N, 70°-95°E) and its relationship with the floating dust weather in the basin during spring. The results show that, there has been a northward shift in the axis of the subtropical westerly jet stream during spring, with a weakening trend in the strength of the jet over these years. The interannual zonal position of the jet stream axis was significantly negatively correlated with the interannual days of the floating dust in the basin. In the years with the more floating dust events in the basin during spring, compared with the less floating dust year, the subtropical westerly jet stream shifts southward, and the zonal wind speed at 200 hPa on the northern side of the jet is relatively high, particularly over the Tarim River Basin, where the wind speed increase is more obvious， the distribution of wind speed field and geopotential height fields at 500 hPa and 850 hPa is also conducive to an increase in surface wind speeds in the basin. As the upper-level westerly wind speed increases, momentum is transferred downward, causing strong surface winds in the Tarim River Basin, which lead to the frequent occurrence of floating dust weather.