Research On The Analysis And Potential Prediction Of Severe Convection Weather In Xinxiang Area

Strong convective weather is a weather phenomenon produced by small and medium-scale weather systems.Its duration is generally short,the affected areas are small and scattered,and they burst strongly.It often causes huge disasters in industrial and agricultural production and life.While the current forecasting and warning of such weather is not accurate enough,so it is vital to conduct strong convective weather prediction research.This thesis,in terms of statistical and synoptic meteorology,studied the cases of strong convective weather in Xinxiang area in the past 12 years,by using the conventional ground and upper-air observation data,the automatic station encryption observation data of Xinxiang area's period of strong convective weather?May to Sept.?in 2005-2016 and the NCEP reanalysis data with a resolution of 1.0°×1.0°.It also classified the weather of strong convective weather,studied the high and low altitude configuration and physical quantity allocation conditions of strong convective weather under different weather conditions,identified typical cases for each type of strong convective weather,conducted synoptic diagnosis analysis to generalize the characteristics of strong convective and the forecasted points towards strong convective weather.The results show that:1.According to high and low altitude conditions,the strong convective weather in Xinxiang area can be divided into four types:?I?Northwest flow type after trough,?II?The cold vortex in North China,?III?Southwest airflow pattern before trough,?IV?deputy High-edge southwest airflow type.2.The frequency of thunderstorms and winds in the Xinxiang area is relatively high.Due to the topographic factors in the northwestern mountainous regions,the frequencies of the three types of strong convective weather are high in the Xinxiang area;the spatial distribution of short-term heavy precipitation and hail presents are more in northwest than southeast.The thunderstorms have gradually decreased since2005,while the short-term heavy precipitation shows a slowly increasing trend;short-term heavy precipitation occurs most frequently during the main flood season?July-August?;thunderstorms are less in September and the other months were on average;hail weather mainly occurs in June and July.The moments when short-term heavy precipitation appeared every day exhibited obvious double-peak data structure characteristics.The peak appeared at 4 a.m.-8 a.m.and 4 p.m.-9 p.m.,and the most frequent occurrence was at 5 a.m..While the diurnal variations of thunderstorm winds and hailstorms showed distinct single-peak structural features,occurring most frequently around the dusk of the day.3.In the case of four types of severe convective weather,there are often rapid jets at 200hPa,Severe convective weather often occurs in the atmosphere where the upper layer of dry cold air is superimposed on the lower layer of warm,moist air.Low trough,Convergence lines and cold air on the ground are the main trigger mechanisms for strong convective weather.4.The four types of strong convective weather have a large value zone with potential pseudoequivalent in the near ground surface,the?_se mean values of type II and type IV are larger than those of other types of strong convection.In the form of distribution,strong convection frequent areas are generally located in large value areas of PW.Four types of strong convective weather mostly occur in the contour dense zone near the northwest of Xinxiang area.Strong convective weather often occurs in where the dry and wet air converge and is close to the path side of the cold air movement.The convergence center of water vapor flux is generally below 900hPa,the mean water vapor flux of type IV is 12 g.hPa^-1.cm^-1.s^-1,and the mean water vapor flux of type I is 5 g.hPa^-1.cm^-1.s^-1.Type I water vapor mainly concentrates below850hPa,while Type II and Type IV vapor belts extend to around 500hPa to 600hPa.Type II is stronger in the vertical transport of water vapor.5.Type I and Type IV convergent ascent centers are mainly located near the ground below 900hPa,while Type II and Type III ascent centers are above 800hPa.The vertical ascent of Type I is greater,and the convergence of Type III and Type IV is stronger.There are strong divergence centers near 200hPa towards the four types of strong convective weather and there are convergence centers in the middle and lower layers.This kind of low-level convergence and high-level divergence atmospheric circulation configuration can generate suction and make the ascending motion stronger,thus making strong convective weather developed rapidly.6.The existence of a positive center of vertical helicity in the middle and lower layers is one of the conditions for the occurrence of strong convective weather,and the positive vertical helicity center has a good correspondence relationship with the strong convection weather.The characteristics of the vertical helicity of type IV strong convective weather are not as obvious as those of the other three types.7.When the southwest wind blows near the ground in the northwestern part of the Xinxiang area,it is easy to generate topographic convergence in front of the windward slope,which is conducive to the development of the vertical upward movement.The warm southwesterly airflow is lifted by the terrain,and the vapor condensation releases latent heat and releases.The latent heat energy provides energy for the development of the ascending movement.The research results in this paper can provide reference for forecasting andearly warning of strong convective weather in the northern part of Henan,especially on the eastern side of the Taihang Mountains,and have practical significance for ensuring the safety of life and property of the people in the region and regional economic and social development.