Dynamic Linkages Between Heat Wave Events In Jianghuai Region And Arctic Summer Cold Anomaly

Summer high temperature events have been occurring with increasing frequency since 2000,which has disastrous consequence for human life and production.During this period,the Arctic sea ice shows a decreasing trend.The significant correlations between the East Asian summer atmospheric circulation,high temperature and high temperature events are proved.On the one hand,the causes and effects of high temperature events in East Asia have been focus of many research efforts.However,the relationship between the high temperature events in East Asia and the cold or warm anomalies in the Arctic during the same period,especially in the seasonal time scale,has received little attention.On the other hand,previous studies have focused on the effects of the SIC/SIE variability on the atmospheric circulation in winter and summer.However,the relationships between sea ice melting and summer atmospheric circulation and high temperature are still insufficient.Therefore,we get two aspects of conclusions:First,based on the reanalysis data of NCEP/NCAR,the main characteristics of atmospheric circulation anomalies and its possible dynamics of Arctic cold anomalies during the summer of 2010,2013 and 2016 were analyzed by using both composite analysis and correlation analysis.The result show that the frequency of occurrence of high temperature events in Jianghuai Region in 2010,2013 and 2016 is significantly higher.During the high temperature events in Jianghuai Region,accompanied by 500 hPa positive geopotential height anomalies,warm anomalies in the mid-and low-tropospheric and weaken westerly winds throughout the troposphere and stratosphere over mid-and low-latitude of East Asian,meanwhile,over most of the Arctic,500 hPa height negative anomalies are corresponded with cold anomalies in the mid-and low-tropospheric and strengthened westerlies throughout the troposphere and stratosphere.Simultaneously,correlation between high temperature events in Jianghuai Region and tropospheric zonal wind is significant positive anomalies,but significant negative anomalies over mid-and low-latitude of East Asian.Evidence suggests that weaken upper westerly winds over the mid-and low-latitude of East Asian suppress convection,thereby reducing cloud cover and enhancing the downwelling surface shortwave radiation,which favors high temperature and heat waves.In this paper,the possible causes of westerly winds anomalies over the Arctic and mid-and low-latitude of East Asian are discussed through the dynamic diagnosis.Then,based on the Arctic sea ice concentration date of Hardly Center,we analysis the temporal and spatial distribution of Arctic sea ice melting over the north of 50°N from May to July and June to September during1979-2016.And the relationships between sea ice melting and summer atmospheric circulation and high temperature are researched by SVD,regression and composite analysis.The result show that there are obvious differences in the Arctic sea ice melting over the north of 50°N in different periods,they both show steady upward trend during 1979 to 2016,however,it took place an obvious interdecadal turn in 2006/2007 from June to September.SVD1 accounts for 64% and 68%,and the correlation coefficients are 0.84 and 0.87 of two periods,respectively.The leading patterns display strong interannual variability superposed on an interdecadal shift.During the two periods,when the PC1 of sea ice melting is in positive phase,is corresponded with warm anomalies in the mid-and low-tropospheric,which is consistent with the variation of atmospheric thickness field under the background of global warming.The significantly correlations between the leading sea ice melting patterns and summer surface temperature anomalies are located in western Russia to Caspian Sea,Black Sea region,West Asia,and East Asia high latitude region.SVD2 accounts for 7% and 10%,and the correlation coefficients are-0.69 and-0.70 of two periods,respectively.The second patterns display strong interannual variability.During the two periods,Arctic sea ice melting is significantly correlated with the frequency of summer mean temperature anomalies and high temperatures in Northwest Europe and East Asia,but the impact on northern Russia was different.During May to July,when the PC2 of sea ice melting is in negative phase,it is dominated by positive anomalies and negative anomalies in a small part of the region,which is corresponded with positive thickness anomalies and a low mean temperature anomaly over the Arctic Ocean.While,the positive and negative atmospheric thickness anomalies alternate in the middle and high latitudes of Eurasia,which is corresponded with positive anomalies both of the frequency of high temperature and average summer temperature.During June to September,it is same as the other period,but the Arctic Ocean is surrounded by positive thickness anomalies.It is found that the Arctic sea ice melting in both two periods causes the northwest of Europe controlled by high pressure,the barotropic structure suppresses convection,thereby reducing cloud cover,which favors high temperature,leads warm anomalies in the mid-and low-tropospheric,while the impact on East Asia is relatively weak.