Relationship Between Mid-latitude Land Surface Thermal Anomalies In Summer Over East Asia And Arctic Sea Ice And Pacific Sea Surface Temperature Anomalies

Based on the data of the sea ice concentration from Hadley Center and the near surface temperature from CRU during 1950-2014,this paper analyzes the variable characteristics of the near surface temperature in summer in the middle latitude of East Asia with the methods of empirical orthogonal function(EOF),linear trend and standard deviation.Some methods are used to reveal the potential mechanism how the Arctic sea ice anomalies affect the near surface thermal anomalies in summer in the middle latitude of East Asia.We also find that both the near surface temperature in the middle latitude of East Asia and the sea surface temperature in northwestern Pacific have the similar variation characteristics,so possible influence of Pacific sea surface temperature anomalies is briefly analyzed.The main conclusions are as follows:(1)Summer near surface temperature in the middle latitude of East Asia shows a consistent warming trend,with the biggest warming variation region located in the region from 40°N to the Lake Baikal.There is a decadal turning point from 1990 to 1996,and significantly warming after the later 1990s.In spring and summer,there is the biggest annual variation in the Greenland Sea and Barents Sea,and both spring and summer ASII have the similar trend.(2)There is a positive correlation between ASII(Arctic Sea Ice Index)and the near surface temperature in the middle latitude of East Asia.More sea ice usually corresponds to obvious summer warming in the middle latitude of East Asia.In the high ASII years,the middle latitude region of East Asia is mainly controlled by the anticyclonic circulation and positive geopotential height anomaly.At the same time,western Siberia is under the control of the cyclonic circulation and negative geopotential height anomaly.So the blocking high in Siberia weakens and the lower troposphere thickness and temperature gradient between the Arctic and middle latitude region enhance.The westly wind enhances and meridional heat transportation weakens between middle and high latitude.The weakening of the blocking high in Siberia and southerly anomalous airflow also lead to the weakening of the flow from the polar region to the middle latitude region and the anomalous warming in the southwest of Lake Baikal.(3)There is a positive correlation between the time series of the near surface temperature over East Asia and sea surface temperature over northwestern Pacific.Significant warming phenomenon occurs in the region of the Lake Baikal while the sea surface temperature increases.The atmospheric circulation over northwestern Pacific shows that obvious positive geopotential height anomaly,anticyclonic circulation and anomalous updraft over northwestern Pacific.Due to the continuity of quality,the lower troposphere shows divergence anomalies over the Lake Baikal and the anticyclonic circulation strengthens.