Study On The Characteristic Evolution And Influence Mechanism Of Jianghuai Cyclones Responding To The Regional Temperature Change Of Cooling And Warming Stages In The Flood Season

In this paper, the influence of temperature stage change on the characteristics of the cyclone in Jianghuai area and its mechanism are analyzed by means of statistical analysis, synthetic analysis and numerical simulation. Firstly, according to the characteristics of temperature changes in the temperature of 1948-2014, this long series can be divided into threen temperature change stages objectively which include the stage that temperature trend is declining(1948-1970),the stage that temperature trend is rising(1971-1994),and the stage that temperature trend is slowly rising(1995-2014). Their characteristics of the temperature stages can be expressed quantitatively with specific temperature indices,which is -2.5,1.15 and 0.42.Secondly,the statistical characteristics of Jianghuai cyclone are compared with temperature trend of each stage,these characteristics include the frequency, life history, extension height and path of the Jianghuai cyclone in three stages. The focus is on the relationship between the evolution of statistical characteristics and the trend of temperature. Jianghuai cyclone is divided into three categories: deep type, shallow type and the bottom type according to extension height. And the typical cyclones of three types were synthesized and analyzed,the structural characteristics of various types of synthetic cyclones were compared and the effect of temperature change on the structure characteristics of syngas was discussed further. Finally, the sensitivity experiment of background temperature of typical Jianghuai cyclone process by WRF numerical model was used to further explore the influence mechanism of background temperature on the characteristics of Jianghuai cyclone. The results are as follows :(1) The statistical results of the three stages of Jianghuai cyclone show that the frequency of cyclone is higher and the life history is longer in the temperature rising stage ,and the development of shallow cyclone is consistent with the change of the temperature in the three stages. Deep and bottom type cyclones are also significantly increased during the temperature risring stage.The cyclone's path is also advancing northward in the stage in the temperature rising stage. These features are well responsive to the trend of changes in the temperature of these stages. The cooling of the stage temperature suppresses the activity of the jianghuai cyclone, and the warming of the temperature promotes the cyclone Development, maintenance and active, and guide the cyclone position northward.(2)The synthesis of cyclone structure shows that the cyclone center strength, temperature gradient, cyclone jet maximum wind speed, the strength, length, position of the cyclone water vapor flux channel and, as well as the strength thickness and position of the two forces: the cyclone's warm and cool air mass, which characterize the cyclonic baroclinic, also the vorticity, divergence, vertical velocity and convective instability of the cyclone center are all related to the cooling, warming and warming slowly of the ambient temperature in the stage. (3) The numerical simulation results show that the influence of the background air temperature characteristics on the cyclone activity is:the temperature changes significantly affect the Jianghuai cyclone's path, the temperature warming, the cyclone to the north while the temperature cooler, cyclone south back. For meridional tracking cyclones, the temperature is warmer and the cyclone that enhance in movement moves slower. The same intensity, the more warm air tend to guide the cyclone position more north. When the background temperature is high,the cyclone intensity is stronger,the maximum wind speed value of the jet area is bigger. The positive heat flux and latent heat flux delivered by the underlying surface will provide more heat for the cyclone and maintain the development of cyclones. And the higher the temperature, the greater the value of the sensible heat flux and the latent heat flux, the more favorable the cyclones' development. When the background temperature is high,the water vapor flux corresponding to the cyclone is larger,the range of the large value area increases,and the water vapor in the cyclone is more abundant.