The Relationship Between Heatwaves And Soil Moisture In North China

This paper aimed at a climate sensitive area, land air interaction region and high heat wave region in north China, the relationship between the soil moisture and heat number is analyzed.Using soil moisture observation data from1981to2001yrs in north China, the spatial distribution of soil moisture in east China area is analyzed, the seasonal and interannual decadal changes are compared by using two sets of reanalysis data including common ERA-40reanalysis data and NCEP-1the applicability in eastern China. On this basis, ERA-40soil moisture data is used for analysis of the relationship between the number of soil moisture and heat wave in north China, and the mechanism of heat waves in north China is discussed as follows:(1) In north China, heat heat numbers on the spatial distribution and temporal change have shown consistent interannual and interdecadal variation characteristics. In the1960s and from90s to the2010, the number of heat waves is high, the number of heat waves in the70s and80s is low, the number of heat waves of heat waves is obviously increased in the1990s.(2) Multi-scale of soil moisture in north China in summer (June-July) is inversly with heat wave number, and the correlation in the early stage is better than the same period. Soil humidity in late May has the most significant influence for summer heat wave frequency; The occurrence peak in June of the average soil moisture significantly associated with the heat number in June. mean soil moisture in July are related to heat number in July.(3) By comparing circulation anomaly characteristics in the low soil moisture years in north China using diagnostic analysis, it is found that:when soil moisture in negative anomaly, in order to maintain the surface heat balance, make the earth’s surface as heat source heat released into the atmosphere, which on the one handleads to surface temperature rising; on the other hand, increasing of sensible heat flux lead to lifting of atmospheric boundary layer thickness. They are all favor for positive anomaly of potential height, which is helpful toincreasing of the western Pacific subtropical high. Under the background of western Pacific subtropical high, air temperature is high due to warming by descending draft.