Analysis Of Dual-Polarization Radar Echoes And The Atmospheric Wind,Temperature And Humidity Structure

Dual-linear polarimetric Doppler radar is the development trend of new generation weather radar.In addition to conventional parameters,polarization parameters can be obtained by dual-polarization radar.By analyzing and retrieving these parameters,the shape,size,phase distribution,spatial orientation and type of precipitation particles can be judged,and micro-physical information of clouds and precipitation can be obtained too.The atmosphere is an integrated system containing various forms of energy.Reaearch on three-dimensional space,especially the atmospheric dynamics,thermal and water vapor conditions and their evolution in the vertical direction and understanding the atmospheric energy structure before strong convective weather can help to extract the precursor information before the strong convective weather and make up for the deficiency of the three-dimensional structure analysis of the small scale weather in conventional weather analysis method.Therefore,this paper focused on the characteristics of the vertical structure of the atmosphere,sounding data,satellite images,etc.were uesd to analyze echoes of dual-polarization radar under different weather conditions.These echoes can be divided into precipitation echoes and non-precipitation echoes according to their characteristics.In the part of non-precipitation echoes,the characteristics of clear air echo and sea clutter were summarized,and we tried to analyze its mechanism.In the precipitation echo part,heavy rain and heavy snows cases were selected,and this paper analyze the cause of weather process and the phase evolution of water condensate in different angles:from PPI to RHl scan data,from conventional parameters to polarization parameters.The main conclusions are as follows:(1)The uneven distribution of refractive index caused by the T,P,e gradient and the turbulence enhancement induced by the background wind field can cause the clear air echo,the echo mechanism is turbulent scattering;the differential reflectivity factor is affected by the Doppler effect.The ZDR of clear air echo has different characteristics in different wind and air turbulence characteristics;the polarization parameter characteristics of sea clutter are:ρHV<0.8,ZDR and ΦDP data are uneven,and the sea clutter is easy to recognize in the precipitation echo with the help of the characteristic of polarization parameters;(2)Polarization parameters can be used to distinguish the phase of the particles and estimate the size of the precipitation,each of which makes contributions:ZDR has a good corresponding relationship with precipitation intensity,ρHV is sensitive to the identification of the melting layer,KDP has a good distinction of heavy rain,but each parameter has its limitations,these parameters can be combined to be used in the actual forecast.(3)Radar data can help to analyze the wind field and dynamic conditions at different stages of heavy snow,and discriminate particle phase in different stages the of snow according to polarization parameters:in the initial stage is mainly wet snow,layered clouds appear layered structure;from the initial stage to the mature stage,snow turns from wet snow to dry snow,the liquid particles are transformed into the ice phase particles,and the dissipation phase changes from dry snow to wet snow.The results not only help to understand the structure and evolution of the atmosphere,but also help to deepen the understanding of the formation mechanism of different echoes,and are of great significance to the quality control of radar echoes and the disastrous weather forecast.