Research On The Analysis And Identification Method Of The Biological Echo Of The New Generation Weather Radar

In order to study the physical characteristics of biological echoes through China new generation weather radar?CINRAD?and the occurrence and development rules of the biological echo by the weather radar in the middle and lower reaches of the Yangtze River,the data observed based on the WSR-88D double polarization weather radar in Shanghai,Nanhui from March to November 2018 were identified and analyzed.The difference between radar parameters and meteorological echo had been discussed based on the electromagnetic scattering theory by reflectivity factor Z of biological echo,large biological equivalent reflectivity Ze,double difference phase?_DP,zero delay correlation coefficients?_HV.The Classification of Echoes by Fuzzy logic Algorithm was compiled based on Python language,the reflectivity texture SD?Z?,differential phase SD(?_DP)reactions such as radar echo small scale numerical change of parameters was obtained by the root mean square method to identify and retain the biological echo information from the weather radar data.In order to study the seasonal occurrence and development of the biological echo detected by weather radar,the dynamic curve changing with the observation time of the biological echo sampling point numbers from the identification results was analyzed.The influence of meteorological conditions such as precipitation,wind and temperature on the migration of organisms were also been discussed in this paper.The results showed that there was no obvious change of biological echo collection quantity in the early March over Shanghai,where was mainly local activity of birds.At night,the insect?s layer first appeared in the middle of March with weak insect activity.The night creatures echo intensity was significantly enhanced in the middle of April to the end of May in Shanghai.The biological echoes was thriving at night without rainfall,or under the sunny weather,with the temperature higher than 16?,and low altitude southern wind with wind force about level 3 or 4 in spring over Shanghai.From early June to the end of August the radar echo of recognition results was given priority to with precipitation.When the stratiform cloud precipitation appeared at night,the biological echo recognition rate was very low.There had shown local activity phenomenon when the accumulated precipitation cloud moved with flying creatures,showed more negative values of the reflectivity factor.During the maximum annual precipitation in the middle and lower reaches of the Yangtze River from the middle of June to late July,the diurnal variation of the biological echoes number was not obvious.Due to the higher temperature about 23?in the night of summer,this was not conducive to the formation and development of the low insect layer and caused a lower weather radar echo recognition rate.At the beginning of September,the recognition rate of biological echo gradually increased.In the sunny nights of September and October,the stratified directional migration of insects was particularly significant.Different from spring,the second peak of biological echo occurred in autumn.When the low-altitude wind direction was northward at night in September and October with wind force less than level 4,the directional migration of insects was significant.For further study,the differences between biological echoes and other non-meteorological echoes with the radar echo parameters during the obvious biological migration period were generated into the normalized frequency histogram.Combining the biological theory,the biological echoes characteristics of radar parameters had been analyzed in different seasons during 2018.The maximum reflectivity factor could reach the light rain magnitude,and mainly appear in the evening or after sunset in the spring and autumn.The proportion of biological echo reflectivity factor with negative value in summer was significantly higher than that in spring and autumn.The polarization parameter of biological echo did not change obviously with the seasons,which was mainly due to the depolarization effect of the radar echo caused by the irregularity of biological scattering monomer,and this had no relationship to the density number of migrating organisms in the radar resolution volume.On the whole,the correlation coefficient of biological echo was generally lower,and the differential reflectivity and two-range differential phase values was higher than meteorological echo.Due to the poor spatial resolution of s-band weather radar,its minimum range resolution was0.25km,which could not observe the monomers of biological echoes such as birds and insects.However,in the spring and autumn of the Yangtze River basin,there had a period of large-scale aerial migration,which could make an effectively identify the phenomenon of stratified directional migration of insects.