Analysis Of The Sensitivity And Difference Based On GPM/DPR Spaceborne Dual Frequency Radar For Detecting Precipitation

Global Precipitation Measurement is the new generation of satellite precipitation products around the world. The GPM Microwave Imager (GMI) carried on the Core Observatory adds high-frequency channels which can detect light rain and snow. The Dual-Frequency Precipitation Radar (DPR) combining the data of Ku-band and Ka-band helps to obtain more information of cloud and precipitation particles.The article analyzes the sensitivity of two wavelengths used by the DPR respectively to the weak and heavy precipitation, and the difference of DPR ,CPR and PR. To detect the cloud and precipitation structure in the typhoon, precipitation distribution, vertical structure, rain top height and structure of stratus cloud and convective cloud of typhoon 'Mujigae' occurred in early October 2015 is analyzed,using 2A-Ku, 2A-Ka and 2A-DPR products of GPM. The detecting results of DPR and ground-based SA-band radar are very close which proves the reliability of DPR data. The mainconclusions of the article are as following:(1) The sensitivity to the precipitation of two wavelengths used by the DPR.In terms of precipitation intensity, ka-band high-precision mode is sensitive to the cloud particles and the weak intensity precipitation. The proportion of the precipitation less than 0.4 mm/h of is the largest.However, when encountering heavy rain,the Ka-band electromagnetic waveattenuation will be weakened which leads to the result that Ka-band can not accurately detect the strong rainfall intensity.The detection of Ka-band MS pattern also has heavy attenuation when encounter heavy rain, but it can hardly detect the rainfall less than 0.2 mm/h. The sensitivity of Ku band to weak intensity precipitation is poorer than ka-band HS pattern.However when detecting heavy rain the attenuation of Ku-band is small, the accuracyof the detecting result is highest. And relative to the Ka-band, Ku band is better at detecting the bright band. The dual-frequency mode can reflect both the condition of the weak precipitation and strong precipitation.In terms of rain top height, no matter which kind of precipitation, Ka-band MS pattern obtainsthe lowestrain top height. When detecting weak precipitation,Ka-band HS pattern detectshigher echo top than that of Ku band; When detecting heavy rain, both of the two bands are similar. This also proves that the rain top height of heavy rain is close to cloud top height, and weak precipitation rain top height is lower than the cloud top height.(2)DPR analyzes structure of typhoon 'Mujigae'.The results show that the Ku-band of DPR is better at detecting precipitation and bright band, however, Ka-band has better effects on detecting small particles of the cloud top. The near-surface precipitation rate centers upon values below 20mm/hr and partly focuses on 20-60mm/h. The maximum value of near-surface precipitation rate is 88.68mm/hr. The rain top height centers on values between 5km and 10km ,the maximum value of which exceeds 15km. The proportion of stratus cloud precipitation in the typhoon reaches 63.4%, but its average rainfall rate per unit area is lower than convective cloud precipitation by 37%.(3)The difference of DPR, CPR and PRAt present, three spaceborne radars havebeen launched. The three radars are PR on the TRMM, CPR on the Cloudsat and DPR on the GPM. PR using Ku band,can detect the heavy precipitation. DPR is the development of PR and uses Ka and Ku wavelength at the same time which can detects both weak precipitation and heavy precipitation. CPR using high frequency W band can detect the structure of the cloud accurately.The article analyzes the convection over the Atlantic on October 3, 2015 using the DPR, CPR data.The rain top height is about 7 km and the cloud top height is about 13 km. The rain top height is 6 km lower than cloud top height. At any height,the reflectivity factor measured by CPR is smaller than the DPR. The echo profiles also present different trends. DPR mainly detectsthe precipitation. CPR detects a wider range of structures, but cannot accurately detect the strong echo centerdue to attenuation.The article compares the convection detected by CPR and PR over the Indian Oceanon February 25, 2015.Detection results of DPR Ku-band and the PR are similar, which verifies the reliability of the DPR data.In addition, the article uses 2B - GEOPROF products from Cloudsat to analyze cloud system structure of typhoon .The cloud top height is about 15 to 17 kmon the whole. With the increase of the distance from the the eye of typhoon,the cloud top height is gradually lower.The rain top height is about 5 km, which is lower than the cloud top height.Ice particles size are mainly distributed in 0-200.Ice particles size is positively correlated with the echo intensity.The particles between 100?m and 200?m are mainly concentrated in 0.5-1 km.Particles above the height aremainly less than 100?m.