Study On Remote Sensing Monitoring And Early Warning Method Of Disastrous Convective Weather Over Qinghai Plateau

Qinghai Plateau(hereinafter referred to as "plateau")has high altitude and complex topography,and frequent disastrous convection.However,there are few studies on severe convection over the plateau,and the application level of satellite and radar is limited,especially on the occurrence and development of severe convection and the characteristics of cloud cluster parameters.In order to do a good job in disaster prevention and mitigation on the plateau and improve the application and research level of remote sensing data,in this paper,conventional meteorological data,ground observation and disaster bulletin data,first-level data of geostationary meteorological satellite and volum scanning data of weather radar from 2005 to 2018 were used.The disastrous convective weather processes were selected,Research on plateau convection mechanism model,characteristic identification and early warning methods had been carried out.The main results are as follows:(1)In view of the data quality problem,this paper improved the data positioning accuracy of FY satellite and Himawari-8 satellite on the plateau by referring to terrain elevation correction and geometric correction methods.And the quality control and echo attenuation correction of radar volume scanning base data were carried out.On this basis,a feasible method of radar echo composite image over the plateau was proposed,and several new composite products were developed.In addition,the parcel method has been used to revise the sounding data in a large amount,and a good correction effect has been obtained.(2)In view of the insufficiency of the study on the convective mechanism over the plateau,the disastrous convective weather was classified in this paper,and the statistical characteristics of the space-time distribution,atmospheric flow field,sounding,development law and organizational structure characteristics of the classified convective weather were obtained over the plateau.On the basis of a large number of sounding and mesoscale analysis and summary of the disastrous convection process,T-log P structure models for classifying severe convection were proposed,and the characteristics of sounding environment parameters of severe convection were obtained.Combined with small and medium scale topography,a mesoscale conceptual model of classified severe convection for various atmospheric flow fields was proposed.Based on the comparative analysis of the observed data of Plateau and plain radiation stations and sounding stations,the mechanism model of convection occurring more easily in plateau than in plain was proposed.The basic principle was that the high altitude of the plateau,the stronger solar radiation and surface long-wave radiation,and the greater temperature rise,all caused the higher vertical decline rate of atmospheric temperature in the plateau,and resulted in the more unstable atmospheric stratification.The characteristics of convective parameters and echo spatial structure of classified severe convective cloud clusters and storm cells at different stages of evolution over the plateau were obtained,and compared with the severe convective structure in the plain.(3)In order to improve the automation and accuracy of the severe convection forecasting over the Qinghai Plateau,The new algorithms for identifying severe convection over the Qinghai Plateau were proposed in this paper,i.e.,the automatic recognition method of radar multi-elevation(calculating the characteristics of velocity convergence,intensity and spectral width at each elevation simultaneously),and the dynamic threshold method of satellite multi-channel(the method of automatic acquisition of initial recognition threshold of severe convective cloud clusters from real-time data is proposed,Extraction of severe convective clouds by reference to multi-channel method for removing cirrus clouds and identifying severe convective Clouds,and the method for further removing cirrus clouds and stratiform clouds by using the edge gradient of cloud clusters was proposed).The strong convective clouds were tracked and identified.The automatic recognition effect was remarkable in the process of severe convective weather.Multiple convective parameters of the identified severe convective cloud clusters and echoes were calculated,and the parameter characteristics for distinguishing different types of severe convection were obtained.(4)In view of the deficiency of the application potential of the new generation meteorological satellite observation data over the plateau,the new generation meteorological satellites(Himawari-8 satellite and FY-4A satellite)to monitor and identify the severe convective cloud clusters were used in this paper.By comparing and analyzing the convective parameters of different types of severe convective clouds,it was found that the plateau convective clouds were mainly cold and deep convection on Himawari-8 satellite and FY-4A satellite cloud images,and FY-4A satellite may also monitor and identify warm and shallow convection.The main shape and position of the severe convective cloud clusters monitored by the two satellites were the same,and the change trend of cloud top brightness temperature was the same.However,the cloud top brightness temperature monitored by FY-4A satellite over the plateau was higher.The reason for the difference between the two satellite observations of cloud top brightness temperature over the plateau was explained by the principle model established.(5)In order to strengthen the scientific support for the severe convection nowcasting system on the plateau,the radar early warning characteristics of hail and non-hail units are studied,and radar early warning algorithms of multiple severe convection types were proposed.The satellite and radar observations data were matched in time and space,and the convective outlines of sever convective clouds and echoes were extracted.The precipitation nature and early warning statistical characteristics of multiple convective parameters in the overlapping range of convective outlines were studied.An early warning method for the severe convective potential(including multiple types of severe convection)observed by satellite and radar was proposed,which was suitable for the complex terrain of the plateau.And the satellite prediction equation of precipitation level was established.The early warning method was tested in the short-time nowcasting operation of severe convective processes,the practice showed that the operational application of the early warning method was feasible.