摘要
In late July and early August 2018,Northeast China suffered from extremely high temperatures,with the maxium temperature anomaly exceeding 6°C.In this study,the large-scale circulation features associated with this heat wave over Northeast China are analyzed using station temperature data and NCEP–NCAR reanalysis data.The results indicate that strong anomalous positive geopotential height centers existed from the lower to upper levels over Northeast China,and the related downward motions were directly responsible for the extreme high-temperature anomalies.The northwestward shift of the western Pacific subtropical high(WPSH)and the northeastward shift of the South Asian high concurrently reinforced the geopotential height anomalies and descending flow over Northeast China.In addition,an anomalous Pacific–Japan pattern in the lower troposphere led to the northwestward shift of the WPSH,jointly favoring the anomalous geopotential height over Northeast China.Two wave trains emanating from the Atlantic region propagated eastwards along high latitudes and midlatitudes,respectively,and converged over Northeast China,leading to the enhancement of the geopotential height anomalies.
本文利用2479个台站的日平均温度的观测资料,分析2018年7月底至8月初我国东北地区发生的极端高温事件的温度特征以及大尺度环流形势特征。此次高温期间东北地区温度距平超过6℃,日平均最高温度超过35℃。结果表明,东北地区上空的反气旋异常伴随的强下沉气流是此次高温的主要成因。西太副高的西伸北跳与南亚高压的东伸共同导致了东北地区上空的反气旋异常,从而加强了该地区的下沉气流;此外,对流层低层850 hPa存在异常的太平洋-日本遥相关(PJ)波列,进一步促进西太副高的西伸。分析对流层上层的波活动发现,北大西洋地区的波动分成两支向下游传播,一支沿中高纬经乌拉尔山地区向东南方向传播;另一支向南传播至地中海附近,而后沿低纬向东传播,最终两支波列汇聚在东北地区上空,加强了该地区的反气旋异常,有利于长波脊的发展。
基金
supported by the National Natural Science Foundation of China under Grant 41775073
