Vertical Pointing Multi-parameter Radar Precipitation And Particle Spectral Profile Retrieval

Particle size distribution(PSD)is an important parameter in the research of precipitation system.Understanding the characteristics of the PSD's vertical profile has important guiding significance for the vertical development of precipitation systems,numerical model prediction,and artificial weather effects.The vertical pointing radar is used to continuously observe the precipitation system.According to the radar parameters such as the obtained echo intensity,the vertical movement speed of the particle and the velocity spectrum width,combined the diameter of the precipitation particle with the free fall velocity,the profile distribution of the PSD can be directly obtained.Then,the profile distribution of precipitation parameters can be retrieved.Precipitation particles have an obvious attenuation effect on short wavelength electromagnetic waves,and the attenuation degree is related to the radar's own wavelength,precipitation intensity and the length of the scattering path.During the study,it was found that the shorter the radar wavelength,the greater the precipitation intensity,and the longer the scattering path length,the greater the attenuation.Due to the fact that vertical airflows of varying degrees are often accompanied by precipitation,the vertical airflow will accelerate or hinder the free fall of precipitation particles,resulting in the measured particle falling speed not equal to the falling speed of particles of the same size in the stationary atmosphere,which makes the retrieval of the PSD error.Through numerical simulation analysis,it is found that subsidence airflow has a greater impact on PSD retrieval than updraft airflow.The low end method of velocity spectrum is used to detect layered cloud precipitation by MRR(micro rain radar).The average falling speed of particles in the area decreases and the rainfall rate increases.In this paper,the observation data about layered cloud precipitation on July 11,2018 in Beijing's Shunyi area of the MRR and the observation data about mixed cloud precipitation on June 11,2015 of the XPR(X-Band profile radar)which belong to the University of Alabama,USA.were read,retrieved and displayed.The results show that in the case of layered cloud precipitation study,the profile of the PSD is basically the same,and the tiny raindrop particles with a diameter of less than 2 mm contribute the most to the precipitation,and the effective particle diameter decreases as the raise of height,and the distribution of rain intensity and liquid water content is coincided with that of echo intensity.In the case study of mixed cloud precipitation,the top of the convective cloud is as high as 12 km,and then the weakened convection gradually evolves into layered cloud precipitation.PSD and precipitation parameters were retrieved for the layered cloud precipitation from 5:30 to 6:29.According to the average particle diameter time-height distribution,the average precipitation particle diameter below 3.5 km is in the range of 2 to 4.5 mm,and it is evenly distributed with the height,and the rainfall rate ranges from 1 to 7 mm/h and liquid water content ranges from 0.05 to 0.5 g/m3,and increase slowly as the raise of height.