Unprecedented East Asian warming in spring 2018 linked to the North Atlantic tripole SST mode

基于ERA-Interim再分析资料,本文研究了2018年春季东亚出现异常增暖的现象,东亚大部分地区比如华南、华北、和日本都在2018年春季观测到了史上最高的地表温度。本文指出,东亚春季异常高温的出现主要与北大西洋三极型海温模态有关,这种海温异常的分布会改变北大西洋上空的斜压不稳定并激发出异常的罗斯贝波列。北大西洋激发的罗斯贝波可以向东传播,随后在东亚上空诱导出异常的高压反气旋,这进一步使得太平洋副高向北移动。与之相对应的,东亚上空出现异常的下沉气流、降水减少和由云量减少引起的太阳辐射增多,同时伴随着从海洋到华南、华北和日本的异常暖平流。大尺度暖平流和局地土壤湿度-气温的反馈作用,都有利于东亚春季异常高温的出现。北大西洋三极型海温模态在前期冬季到后期春季有很强的记忆能力,这对提高东亚天气和气候的预报可能提供有益的启示。

An unusually warm East Asia in spring 2018,when exceptionally high surface air temperatures were recorded in large areas of Asia,such as northern China,southern China,and Japan,was investigated based on the ERA-Interim reanalysis.The East Asian warming anomalies were primarily attributed to a tripole mode of North Atlantic SST anomalies,which could have triggered anomalous Rossby wave trains over the North Atlantic and Eurasia through modulating the North Atlantic baroclinic instability.Atlantic-forced Rossby waves tend to propagate eastward and induce anomalously high pressure and anticyclonic activity over East Asia,leading to a northward displacement of the Pacific subtropical high.As a result,descending motion,reduced precipitation,and increased surface solar radiation due to less cloud cover appear over East Asia,accompanied by remarkably warm advection from the ocean to southern China,northern China,and Japan.The transportation of anomalously warm advection and the feedbacks between soil moisture and surface temperature were both favorable for the recordbreaking warmth in East Asia during spring 2018.The seasonal‘memory’of the North Atlantic tripole SST mode from the previous winter to the following spring may provide useful implications for the seasonal prediction of East Asian weather and climate.