2021/2022年冬季中国气候异常特征及南方降水异常偏多成因分析

Characteristics of Climate Anomalies over China in Winter 2021/2022 and Causes for Precipitation Anomalies over Southern China

2021/2022年冬季,东亚冬季风较常年同期偏强,西伯利亚高压偏强,我国平均气温较常年同期偏低,在空间型上整体表现为“北暖南冷”的异常分布,全国平均降水量较常年同期偏多,尤其是青藏高原、西南、华南等地偏多较为明显。冬季北极涛动长时间维持正位相,有利于乌拉尔山阻塞高压偏弱;而鄂霍次克海阻塞高压异常活跃,500 hPa高度场上正距平中心从鄂霍次克海向西延伸至贝加尔湖—巴尔喀什湖附近;此外,冬季北极涛动正位相还通过南欧亚遥相关型的间接途径影响东亚冬季气候,造成中东急流偏强,高原高度场持续偏低,与赤道中东太平洋的La Nina事件相配合,使得东亚地区500 hPa高度场整体呈现近似“北高南低”的距平分布,我国冬季平均气温在空间型上整体表现为“北暖南冷”的异常分布,南方地区降水异常偏多。在季节内变化方面,我国冬季气温呈现“前冬暖、后冬冷”的特点,主要与东亚冬季风“前冬偏弱、后冬偏强”的季节内变化特征密切相关。

The East Asian winter monsoon and the Siberian high were both stronger than normal during the 2021/2022 winter.Temperature over China was colder than normal in winter,and the overall spatial feature was“warmer in Northern China and colder in Southern China”.Precipitation over China was more than normal,especially in the Qinghai-Tibetan Plateau,Southwest China and South China.The Arctic Oscillation maintained a positive phase for a long time in winter,in favorable for the weak Ural Mountain blocking high.The Okhotsk blocking high was abnormally active,and the center of the positive anomaly at the 500 hPa height field extended westward from the Sea of Okhotsk to Lake Baikal-Lake Balkhash.In addition,the positive phase of the Arctic Oscillation in winter also affected East Asia by an indirect way of the southern Eurasian teleconnection,leading to a stronger Middle East jet stream and a persistently lower height field in Tibetan Plateau.Coordinated with the La Nina event,the 500 hPa height field over East Asia presented a“higher in the north and lower in the south”pattern,thus temperature over China showed an anomalous distribution of“warmer in the Northern China and colder in Southern China”,and precipitation over Southern China was more than normal.Temperature over China was“warmer in the earlier winter and colder in the later winter”,which was closely related to the intraseasonal variation of the East Asian winter monsoon,which was“weaker in the earlier winter and stronger in the later winter”.