北极海冰年际变化对东亚中纬度夏季陆面热力异常的指示作用及其可能原因

本文分析了夏季东亚中纬度近地面温度和春、夏北极海冰时空变化特征,探讨了格陵兰海、巴伦支海海冰异常变化与夏季东亚中纬度陆面热力异常在年际上的可能联系。结果表明:(1)1950—2014年,东亚中纬度夏季近地面温度明显增暖,并伴有明显的年际变化,年际变率最大值的区域主要位于40°N以北至贝加尔湖地区;春、夏格陵兰海和巴伦支海的海冰也呈现明显的减少趋势,同时表现出较强的年际变化特征。(2)春、夏格陵兰海、巴伦支海海冰异常对东亚中纬度夏季陆面热力异常具有一定的指示作用:春、夏格陵兰海、巴伦支海海冰异常偏多,通常对应夏季东亚中纬度近地面的东亚中纬度夏季增暖现象;反之亦然。(3)春、季格陵兰海、巴伦支海北极海冰指数(Arctic Sea Ice Index,ASII)高值年(海冰异常偏多年份),贝加尔湖及西南的蒙古高原地区通常为大范围的异常高压控制,有利于近地面温度升高;同时由于乌拉尔山阻塞高压减弱,极地南下的冷空气减弱,有利于东亚中纬度区域的温度升高。而ASII低值年的情形则相反,贝加尔湖以南地区受异常低压控制,乌拉尔山阻塞高压增强,冷空气易向南侵袭,不利于东亚中纬度近地面升温。

Indicative role of interannual variations of Arctic sea ice on summer land surface thermal anomalies in the mid-latitude of East Asia and its possible cause

This paper first analyzes the temporal and spatial variation characteristics of the summer near-surface temperature in the mid-latitude of East Asia and the sea ice in the Arctic in spring and summer, and further discusses the possible interannual relationship between the sea ice anomaly changes in the Greenland Sea and Barents Sea and the summer land surface thermal anomaly in the mid-latitude of East Asia. Then the possible linkages between the interannual variations of spring and summer Arctic sea ice and summer land surface thermal anomalies have been explored. Results suggest that the land surface in the middle latitude of East Asia has experienced significant warming during 1950 to 2014, which was also accompanied by strong interannual variability especially in the south of the Lake Baikal. Meanwhile, both spring and summer Arctic sea ice decreased evidently and exhibits evident interannual difference, especially in the Greenland Sea and the Barents Sea. The spring and summer sea ice over those regions shows close relationship with the summer land surface thermal anomalies over East Asia. More (less) sea ice usually corresponds evident summer warming (cooling) in the middle latitude of the East Asia. Further analysis shows that more (less) sea ice tends to cause positive (negative) geopotential height anomalies in the south of the Lake Baikal and weakened (strengthened) blocking high near the Ural Mountain and weaker (stronger) cold air activity, which benefits the warming (cooling) of the middle latitude of the East Asia.