2022年夏季中国高温的环流异常特征

基于美国国家海洋和大气管理局(National Oceanic and Atmospheric Administration,NOAA)全球范围扩展重建海面温度资料第5版本(Extended Reconstructed Sea Surface Temperature version 5,ERSSTv5),以及美国国家环境预报中心和国家大气研究中心NCEP(National Centers for Environmental Prediction)/NCAR(National Center for Atmospheric Research)逐月全球再分析资料,采用相关、回归、合成及物理量诊断等方法,对2022年夏季中国大范围高温相关环流异常的可能成因进行了分析。结果表明:(1)2022年夏季南亚高压偏强并分别向东、西方向扩展,西太平洋副热带高压(以下简称“副高”)异常偏强西伸。2022夏季为拉尼娜(La Niña)年,但热带大西洋垂直上升环流相对西太平洋更强,且热带印度洋到西太平洋热带垂直上升环流异常也偏强。(2)2022年热带大西洋、印度洋到西太平洋上空垂直环流异常和La Niña共同作用,使得夏季南亚高压和西太平洋副高极端异常。La Niña和印度洋到西太平洋垂直环流异常有利于南亚高压和西太平洋副高的偏强西伸;热带大西洋环流异常则既有利于南亚高压的加强及东扩,也有利于西太平洋副高偏强西伸。(3)印度洋到西太平洋垂直环流主要通过局地经向哈得来(Hadley)环流影响青藏高原到中国东部的环流异常,表现为青藏高原到中国东部中低层为显著的辐散异常;热带大西洋则通过引起纬向风异常(急流异常),激发遥相关波列并向下游传播,进而影响青藏高原到中国东部地区的环流异常。

Characteristics of circulation anomalies associated with the heat-wave events over China in summer 2022

Based on NOAA (National Oceanic and Atmospheric Administration) ERSSTv5 (Extended Reconstructed Sea Surface Temperature version 5) and monthly reanalysis data from NCEP(National Centers for Environmental Prediction)/NCAR(National Center for Atmospheric Research), the possible causes of the circulation anomalies related to the wide-range heat-wave events in summer (JJA, from June to August) 2022 over China are investigated by correlation, regression, composite analysis, and diagnosis of physical quantities. The results are shown below. (1) The SAH (South Asia high) in JJA 2022 is strong and extends eastward and westward, and the WPSH (western Pacific subtropical high) is also strong and extends westward. It is in phase of La Niña during summer 2022, but the vertical ascending circulations over the TA (tropical Atlantic) are stronger than those over the WP (western Pacific), and the vertical ascending circulations from the TIO (tropical Indian Ocean) to WP are also abnormally strong. (2) The combined effects of anomalous vertical circulations over TA, TIO, WP and La Niña result in the extreme abnormalities of SAH and WPSH in JJA 2022. La Niña and the abnormally strong vertical circulations from TIO to WP are helpful for the strengthening and westward expansion of SAH and WPSH. The abnormal vertical circulations over TA tend to help not only the strengthening and eastward expansion of SAH, but also the strengthening and westward expansion of WPSH. (3) The vertical circulations from TIO to WP mainly affect the circulation anomalies from the TP (Tibetan Plateau) to eastern China through local meridional Hadley circulation, characterized by the significant divergence anomaly from TP to eastern China in the mid- and low levels. However, the vertical circulations over TA can stimulate teleconnection wave train and then propagate downstream by causing zonal wind anomalies (jet stream anomalies), which then affect the circulation anomalies from TP to eastern China.