Linkages Among Soil Moisture,Cyclone Activity And Summer Anomalous Warming Of The Land Surface In The Mid Latitudes Of East Asia

Based on the reanalysis data of the ERA-Interim during 1979-2015,the spatial and temporal distribution characteristics of the land surface thermal over the mid latitude of East Asia in summer are analyzed and the number of East Asian cyclone tracks in summer are identified by utilizing the objective identification and tracking method.Furthermore,the relationship between cyclone activity and anomaly warming in mid latitude of East Asia is discussed,and the possible mechanism of cyclones activity affecting the land surface is analyzed from the perspective of atmospheric circulation,cloud cover and precipitation.Finally,the relationship between the early spring soil moisture and the anomaly warming in the mid latitude of East Asia in summer and its possible influence are also briefly analyzed.The main conclusions are as follows:(1)Summer surface temperature of soil is uniformly warming in the whole mid latitude of East Asia region during 1979-2015 and the most warming area is in the Lake Baikal area,so we choose this area as the land surface thermal key area(45-55°N,85-115°E)over the mid latitude of East Asia.There is an interdecadal change of temperature from low to high over key area.(2)The most frequent cyclone activity in spring and summer in East Asia are located in the central part of Mongolia to the northern part of Northeast China(mainly located in the latitudinal zone of 45 to 55 degrees north latitude).Meanwhile,the cyclone activity in this area is also the most variable.The spatial distribution of the cyclone intensity in spring and summer is very similar to the cyclonic frequency,but the variation rate of the cyclone intensity is small.Therefore,the central Mongolia to the north of Northeast China as a key area of spring and summer cyclone activity(40-55°N,80-140°E),the statistics of cyclone tracks number in the area,found that the summer cyclone activity was significantly less trend,there is a characteristic of interdecadal change from high to low.(3)There is a significant negative correlation between the summer cyclone activity and the soil surface temperature in the Lake Baikal area.Namely,the large value area of the regression coefficient of soil surface temperature is selected as the key area(45-55°N,85-115°E),and the surface temperature in the key area decreases when the cyclone activity is strong,otherwise,the temperature increases.There is more cloud in the key area when the cyclone activity is strong in summer,thus reducing the downward solar radiation that the surface receives,and simultaneously the precipitation rises which results in the increase of soil humidity and latent heat release and the enhancement of evaporative cooling.Finally,the soil temperature will be lower.The atmospheric Circulation is characterized by the strong cyclonic circulation in the Lake Baikal area and the anticyelonic circulation in the east of Ural,and this kind of spatial configuration is conducive to the enhancement of the northerly airflow in the rear of the cyclone and the front of the anticyclone,guiding the cold air to the key areas.Meanwhile,the westerly wind in the southern side of the cyclonic circulation strengthens the westerly wind in the 40°N,and the heat exchange between the north and the South is weakened significantly,which is unfavorable for the south of warm air to enter the key area.Moreover,abnormal circulation makes the low level horizontal temperature advection in the key area shows a significant negative anomaly,further triggering the decrease of the surface temperature of the soil in the key areas.(4)There is a significant positive correlation between the spring soil moisture in West Siberia to Lake Baikal area(55-70°N,65-100°E)and the summer soil surface temperature in the Lake Baikal area,also the soi1 moisture has a good memory which can sustain to summer.The surface of soil temperature in the key area rise in the summer and the positive geopotential height anomaly and anticyclonic circulation over Lake Baikal area when the soil moisture is high,otherwise the temperature decreases and cyclonic circulation over Lake Baikal area.There is less Cloudiness in the key area and high soil moisture in summer over West Siberia to Lake Baikal area when the soil moisture is high in spring over Lake Baikal area,resulting the surface temperature of soil increase.