The Spatial And Temporal Distribution Of Chinese Tornado And Its Characteristic Analysis Of Environmental Parameters

Tornado is one of the important weather disasters in our country. Along with deep convection weather, with strong local, sudden eruptible and small scale characteristics, tornado is extremely hard to monitor and predict. So analyzing the spatial and temporal distribution and interaction with environmental field has a practical application value to deepen the understanding of the tornado genesis and development and exploring its mechanism. Using data of Chinese meteorological disasters yearbook from 2004 to 2012 and CFSR reanalysis, according to the method of statistics and synthetic analysis, this paper systematically analyzes the spatial and temporal distribution characteristic of tornadoes in China, environmental background field and the characteristics of environmental parameters in three tornado-prone region for the frequency. The main conclusions are as follows:First of all, in the matter of spatial and temporal distribution, In the 9 years from 2004 to 2012,the tornado days and tornadoes in China decrease first, then increase from 2004 to 2012 generally. They occurred most frequently in spring and summer, in the afternoon and at dust. And they occurred most frequently over plains of Eastern China, Central China and southern China especially in Jiangsu and Guangdong province in recent 10 years.Secondly, in the matter of background situation, there are certain circulation background differences in three tornado-prone region for the frequency, the upper level trough at 500 hPa,shear line and low level southwest jet at 850 hPa provide a favorable environmental background field for " Jiangsu and its adjacent region"; Before the tornado events in "Guangdong and its adjacent region", they are controlled by southwester at 850 hPa, and then straight west wind at 500 hPa; While tornadoes in "Northeast region" stay unstable, they are controlled by the deep Northeast cold vortex mainly.Thirdly, in the matter of the thermodynamical structure,tornado-prone regions for the frequency in " Jiangsu and its adjacent region" and "Guangdong and its adjacent region" are located at the junction of CAPE and SRH value centers. And before the tornado events, the surface specific humidity advection increases the low-level humidity, leading to a unstable stratification. The mean CAPE and SLI values of "Northeast region" are very low, the mean specific humidity is far lower than those of "Jiangsu and its adjacent region" and "Guangdong and its adjacent region", but with higher upper and lower-level lapse rate and larger middle and lower-level vertical wind shear, there is also possibility for tornado occurrence because of strong dynamical trigger condition.Lastly, in the matter of occurred conditions, the distribution of EHI and STP has a high concordance with positions of three tornado-prone region for the frequency. The high value centers of EHI and STP in " Jiangsu and its adjacent region" are distributed in central and southern Jiangsu province. The high value centers of EHI and STP in "Northeast region" are distributed at the junction of Liaoning, Jilin and Inner Mongolia. The high value centers of EHI and STP in " Guangdong and its adjacent region" are distributed at the junction of Guangdong and Guangxi, by southwest direction of the tornado-prone region. So even in different regions, there are some regional differences in environmental background, but severe weather index especially helicity, vertical wind shear and STP have certain application value and indicative meaning for tornado occurrence forecast and warming.