2022年夏季西太平洋副热带高压异常强盛且稳定维持与长江中下游持续性极端高温事件

Anomalously strong and stable maintenance of Western Pacific Subtropical High in the boreal summer of 2022 and the persistent extreme high temperature events in the middle and lower reaches of the Yangtze River

中文关键词:  极端高温 西太平洋副热带高压 维持机制 长江中下游 2022年

英文关键词:Extreme high temperature event,Western Pacific Subtropical High, Maintenance mechanism, The middle and lower reaches of the Yangtze River, 2022

中文摘要:

      022年夏季长江中下游地区发生了1960年以来的最强的高温事件，其形成和维持与西太平洋副热带高压（WPSH）异常强盛有关。[资料和方法]利用站点观测资料和再分析资料，通过对不同变量的诊断分析，[目的]研究了高温时段WPSH异常强盛且稳定维持的机制，得到如下结论：[结果]（1）在高温时段，长江中下游地区盛行比一般高温年更强的下沉运动，扰动垂直动力加热是长江中下游地区高温维持的主要因素。短波辐射通量表现为向下的异常，可通过向上的感热通量将热量由地面传输至近地层空气并促使其增热。（2）与一般高温年不同，2022年WPSH与南亚高压（SAH）重叠于长江中下游地区，利于WPSH在大陆上空维持，为此次极端高温事件的出现提供了有利的环流条件。WPSH强度维持与局地负涡度的维持有关。一是扰动负涡度的垂直向下输送，二是相对涡度水平平流负异常。特别是，在长江中下游地区上空WPSH的维持，自上而下的负涡度的垂直输送起着极为重要的作用。（3）不同于一般高温年，WPSH在海洋上的主体部分的维持主要与180o附近赤道中太平洋海温异常偏冷有关。而WPSH在大陆上的部分的维持与菲律宾群岛附近对流关系密切，其有利于长江中下游地区上空负涡度的维持。[结论]研究结果将加深对WPSH变化成因的认识，为后续研究持续高温的成因提供理论基础。

英文摘要:

      The strongest high-temperature event since 1960 occurred in the middle and lower reaches of the Yangtze River in the summer of 2022, and its formation and maintenance are related to the anomalous strong Western Pacific Subtropical High (WPSH). By using station observational data, reanalysis data, and diagnostic analysis of different variables, the manuscript investigated the mechanism of the anomalously strong and stable maintenance of the WPSH during the high temperature period. The results are as follows. (1) During the high temperature period, stronger sinking movements are prevalent in the middle and lower reaches of the Yangtze River compared to typical high temperature years, and the perturbation vertical dynamic heating term is the main factor for maintaining high temperatures in this region. Anomalous downward shortwave radiation flux can lead to transfer heat from the ground to the lower atmosphere through upward sensible heat flux, promoting surface heating. (2) Unlike typical high temperature years, the overlap of WPSH and South Asian High (SAH) facilitate the maintenance of WPSH over the middle and lower reaches of the Yangtze River, providing favorable circulation conditions for this extreme high temperature event. The maintenance of WPSH intensity was related to the local negative vorticity. One is the vertical downward transport of disturbance negative vorticity, and the other is the negative anomaly of relative vorticity horizontal advection. Especially, the vertical transport of negative vorticity from top to bottom plays a crucial role on maintaining WPSH over the middle and lower reaches of the Yangtze River. (3) Unlike typical high temperature years, the maintenance of the WPSH oceanic core was mainly related to the anomalously cold sea surface temperature near 180° around the equatorial central Pacific. The maintenance of the continental part of WPSH was closely related to convection near the Philippine Islands, which is beneficial for maintaining negative vorticity over the middle and lower reaches of the Yangtze River. The research results will deepen the understanding of the causes of WPSH variability, providing a theoretical basis for subsequent studies on the causes of persistent high temperatures.