35GHz Millimeter Wave Cloud Radar Boundary Layer Precipitation Inversion Analysis

Cloud radar has high spatial and temporal resolution and mainly has been used in physics of rain and cloud research,such as retrieving height,thickness and type of cloud to get better understanding of cloud development.However there is a serious attenuation of cloud radar which makes it less used in precipitation research.The boundary layer is the layer close to the ground.It's very important to the initiation of weather events for the characters in this layer.Therefore,studying the characteristics of the atmospheric boundary layer is very important for analyzing the weather phenomena.In this paper,we make attenuation correction in 35GHz cloud radar and choose some representative data to analyze precipitation.We also evaluate the observation ability of stratiform cloud precipitation and convective cloud precipitation by cloud radar,retrieve cloud parameters,and analyze the characteristics of boundary height.The main contents of this study are as follows:(1)According to the relationship between the reflectivity factor and the attenuation coefficient k,the attenuation correction of the weather observed in the 35GHz cloud radar is carried out by the method of bin-by-bin correction.The stratiform cloud,the stratiform precipitation,the convective cloud,the convective precipitation and the cirrus cloud are mainly corrected.The results show that cloud cannot be revised more than 1dBZ,and the maximum correction for precipitation can be up to 6dBZ.(2)For the parameters,such as liquid water content,liquid water path and rainwater path,C band radar data corresponding to the location of Cloud Radar was selected to retrieve the parameters.The results show that the cloud liquid water path under precipitation is generally 0-3000g/m~2 but there exists error.Therefore,it is commonly used to retrieve stratiform cloud precipitation,but has large error about convective precipitation.(3)We select the reflectivity,velocity and spectral width of Cloud Radar to compare with the C band radar.Calculate the layer average reflectivity and standard deviation to distinguish stratiform precipitation and convective precipitation,in addition,analyze the precipitation performance.The results show that the cloud radar is more suitable for the stratiform precipitation,but not suitable for the convective precipitation.If the cloud radar can observe the obvious bright band,the precipitation is stratiform precipitation.If the reflectivity of the cloud radar has obvious echo columns and the average reflectivity is turbulence,it is convective precipitation.Sometimes,cloud radar can detect dark zone above the bright band,this is due to ice sublimation which make the ambient temperature rises,causing upward airflow,so the liquid particles upward,resulting in reflectivity reduce.Using cloud radar to retrieve CLWP should be used in stratiform precipitation,if in convective precipitation,it will cause big uncertainty.(4)There is a big variation about the atmospheric boundary layer,which usually change in 400m to 2000m.And the daytime height always higher than night.After 8:00pm,the boundary height decrease first and then gradually increase.It also affected by the precipitation.When precipitation occurs,the height will decrease.In non-precipitation situation,if there are cloud in the sky,the reflectivity above the boundary height always higher than the reflectivity under the boundary height.But if it rains,the reflectivity will be opposite.