江淮地区夏季高温事件与北极冷异常的动力联系

利用NCEP/NCAR再分析资料，通过合成分析和相关分析，研究了2010年、2013年及2016年夏季江淮地区高温事件发生时，大气环流异常的主要特征及其与北极冷异常的可能联系。结果表明:这3年江淮地区夏季高温事件发生频次明显偏高，期间江淮地区500 hPa位势高度为正异常，对流层中低层平均温度为暖异常，整个对流层和平流层纬向风减弱；而北极500 hPa高度为负异常，对流层中低层平均温度异常偏冷，纬向风明显加强。因此，江淮地区高温事件与对流层纬向风存在密切联系，在东亚中低纬度地区呈负相关，而在北极呈正相关。东亚中低纬度地区对流层西风减弱抑制对流活动，地面吸收太阳短波辐射增加，进而有利于高温事件发生。

Dynamic Linkages Between Heat Wave Events in Jianghuai Region and Arctic Summer Cold Anomaly

Summer high temperature events have been occurring with increasing frequency since 2000, which have disastrous consequence for society, economy and human production and life. During recent years, causes and effects of high temperature events in East Asia have been focused in many research efforts. However, relationships between high temperature events in East Asia summer and cold or warm anomalies in the Arctic during the same period, especially in the seasonal time scale, attract little attention.
Based on reanalysis data of NCEP/NCAR, main characteristics of atmospheric circulation anomalies and its possible dynamics of Arctic cold anomalies during the summer of 2010, 2013 and 2016, are analyzed by using both composite analysis and correlation analysis. Results show that the frequency of high temperature events in East Asia is complex. High temperature events occurred in Jianghuai Region accompanied by 500 hPa positive geopotential height anomalies, warm anomalies in the middle and low tropospheric, weakened westerly winds throughout the troposphere and stratosphere over middle and low latitudes of East Asian. And meanwhile, over most of the Arctic, 500 hPa height negative anomalies are corresponded with 500-1000 hPa negative thickness anomalies, cold anomalies in the middle and low tropospheric and strengthened westerlies throughout the troposphere and stratosphere. Results show that the high temperature events in Jianghuai Region of 2010, 2013 and 2016 are closely related to the tropospheric zonal wind. It shows that high temperature events in Jianghuai Region is negatively correlated with the tropospheric zonal wind in middle and low latitudes of East Asia, while positively correlated with that over Arctic areas. It''s also found that this correlation is not limited to 200 hPa, which occurs through the troposphere and stratosphere. Evidence suggests that during the high temperature events in Jianghuai Region of 2010, 2013 and 2016, weakened upper westerly winds over the middle and low latitudes of East Asian enhance barotropy and decrease baroclinity in this area, which suppress convection and have great contributions to the generation and maintenance of anticyclone. Thereby resulting in reduced cloud cover and enhancing the downwelling surface shortwave radiation, which contributes to increase heat waves. Possible causes of westerly winds anomalies over the Arctic and mid-and low-latitudes of East Asia during high temperature events in Jianghuai Region are also discussed through dynamic diagnosis.