Abstract:

In this paper, monthly NCEP/NCAR reanalysis data from 1961 to 2016 and daily precipitation observation data obtained from 20 meteorology stations in Ningxia were used to analyze the anomalous characteristics of East Asian subtropical jet(EASJ) in the spring precipitation anomalies years in Ningxia. The possible causes were analyzed briefly. The results show that at the same period and in the previous period of spring precipitation anomalies years, there was spatial structure anomaly for the subtropical zonal wind and the anti-phase features were more significant in the range of 110°E-160°E. EASJ enhanced in the same and previous period of the year with precipitation abnormally less, and weakened when it was abnormally more in both the horizontal and vertical directions. But the out-of-phase relation in the previous period was not as significant as that in the same period. A subtropical jet stream index in spring was established. When the subtropical jet stream index was negative anomaly, the East Asian major trough was deepened more than normal and not conducive to the northward shift of the subtropical high. The wind field on 850 hPa was also affected by the north wind anomalies, which was not conducive to the formation of precipitation.

Key words: Ningxia, spring precipitation, East Asia subtropical jet

摘要：

利用1961—2016年NCEP/NCAR逐月再分析资料和宁夏20个气象台站逐日降水观测资料，分析宁夏春季降水异常年东亚副热带急流异常特征，并简要分析可能影响原因。结果表明：春季降水异常年同期及前期，副热带纬向风均存在空间结构异常，且在110°E—160°E异常年反位相特征表现更显著。在降水异常偏少（多）年同期及前期，水平及垂直方向上均存在东亚副热带急流区西风增强（减弱），但前期反位相对应关系不如同期明显；建立的春季东亚副热带急流指数与宁夏春季降水呈显著正相关，春季东亚副热带急流指数为负（正）异常时，东亚大槽较常年加深（略浅），宁夏地区受西北（南支）气流影响，850 hPa风场也表现为偏北风（偏南风）距平，不利于（有利于）形成降水。

关键词: 宁夏, 春季降水, 东亚副热带急流