Impact Of Snow Cover Anomaly Over The Mid-high Latitudes Of The Eurasian Continent On Summer Low Temperature In The Northeast China

Using the NSIDC (The National Snow and Ice Data Center) global monthly EASE (Equal-Area Scalable Earth)—Grid snow water equivalent data during the period1979—2007, NCEP/NCAR monthly reanalysis data and daily data observed at743stations in China, we explored the basic characteristics of summer low temperature in the Northeast China and the snowmelt over the Eurasian Continent. Moreover, the relationship between the snowmelt anomaly over the mid-high latitudes of the Eurasian continent and summer surface air temperature in the Northeast China and the possible physical mechanisms are also investigated. Conclusions are as follow:(1) Under the background of global warming, significant warming trend of averaged temperature over the Northeast China happens, and increased variability and instability of the climate are also detected in this region(2) In recent30years, the variations of the snowmelt in the Eurasian continent are featured as:more spring snowmelt takes place in west part of the continent than its east part. Significant summer snowmelt mainly locates in the northeast of the continent; There is an significant negative correlation between spring and summer snowmelt, i.e., less summer snowmelt is always accompanied by more spring snowmelt.(3) Summer temperature in the Northeast China bears close relationship with the anomalous snowmelt over the mid-high latitudes of the Eurasian continent. less (more) spring snowmelt as well as more (less) summer snowmelt in the mid-high latitudes of the western Eurasia usually result in cool (warm) summer in the Northeast China. (4) The possible physical mechanisms that the anomalous distribution of the spring snowmelt over the mid-high latitudes of the eastern Eurasia affects the summer temperature of the Northeast China could be summarized as following: Less(more) spring snowmelt tends to increase(decrease) the summer snow cover in the same areas. More(less) summer snowmelt and higher(lower) soil water content in the mid-high latitudes of the east Eurasia will lower(higher) the summer air temperature over these regions. As a results, the geopotential height is decreased(increased) and the long wave troughs at500hPa is deepened(shallower), which will strengthen(weaken) the northly wind behind the trough. Under such a situation, the cold air flow from the polar region is easy(hard) to invade in the mid-high latitude of eas Asia, resulting in cool (warm) summer in the Northeast China.