Ka-band Cloud Radar Data Quality Control And Statistical Analysis Of Cloud Vertical Structure In Beijing Area

Cloud is a visible polymer suspended in the atmosphere by a moist air lifted and cooled to a saturation,and it plays an extremely important role in the water vapor transmission of the earth and regulation and indication of weather and climate change.The cloud can regulate the radiation energy balance of earth-atmosphere system.The value of cloud radiative forcing depends on the macro and micro structure of the cloud.The vertical resolution of atmospheric mode depends on information such as cloud thickness and spacing between clouds.With the development of detection technology,millimeter wave radar has become an indispensable method in cloud observation because of its long time continuous observation ability,narrow beam(strong anti-interference ability)and high spatial and temporal resolution.This paper carries out the following three aspects by using the base Ka band millimeter-wave radar data of the institute of atmospheric physics of Chinese academy of sciences:1.This paper uses the observation data of 2014 to statistics and analysis the distribution of non-cloud echo in Beijing area and put forward quality control method.The effect of this method was analyzed by using data of Ka band millimeter wave radar in Beijing from 2014 to 2016.The results show that the clutter has distinct seasons and highly distributed characteristics in cloudless weather.The altitude distribution of Z in Spring,summer and autumn are mainly distributed under 3km higher than winter,and the main distribution range of LDR is greater than-18 dB,the Z distribution of spring and summer is less than-15 dBZ.The main distribution of Z in autumn is less than-20 dBZ.In winter,the altitude distribution is within 2km,and the main distribution range of LDR is greater than-14 dB.In spring and summer,the distribution range of Z is less than-30 dBZ.In cloudless weather,the success rate of clutter suppression can reach 99%.In cloud weather,it can filter the influence of low air suspended clutter on cloud echo,while retaining cloud echo.2.The echo attenuation is serious of Ka-band millimeter-wave radar in precipitation,it not applicable to precipitation observation.This paper mainly analyzes the vertical structure of non-precipitation cloud and statistics of precipitation data in 2014 and determine the conditions of precipitation judgment and test it.The results show that the accuracy of precipitation judgment is greater than 95%,which can recognize the precipitation echo well.3.Calculating the vertical structure characteristics of cloud in Beijing area from 2014 to 2016 :(1)The incidence of cloud in Beijing has obvious distribution characteristics.The average incidence was 31.37% and the average incidence of precipitation cloud was 5.37%.The incidence rate was the highest(54.21%)in June,the lowest incidence rate(12%)in February,and the highest incidence(14.16%)of precipitation cloud in June.There was little precipitation in January and December,and the lowest incidence(0.78%)in December.The incidence rate of Monolayer cloud is 63.98%,the highest incidence(76.23%)in February,and the lowest incidence(42.53%)in September.In the multi-layer cloud,the average incidence is 26.86% of two-layer clouds with an average space thickness of 1.91 km.The occurrence rate of the three-layer cloud was the highest in September(16.93%).The mean space thickness between the middle layer and the upper layer was 1.62 km,while the average space thickness between the middle layer and the lower layer was 1.45 km.(2)According to the statistics of lowest cloud base and highest cloud top,the lowest height of average cloud base is 4.19 km,and the highest height of average cloud top is 6.95 km.Cloud thickness has no obvious monthly change and seasonal variation with an average thickness of 2.76 km.The overall distribution trend of the average Z in the cloud decreases with the increase of cloud height.(3)The seasonal distribution features of low,medium and high clouds in Beijing are consistent,with the medium and high clouds as the main,and the low clouds less than 10%.The highest number of clouds(74.51%)in summer and the highest in winter(53.01%).