Vertical profile of raindrop size distribution by using 400MHz wind profiler in stratiform rainfall

To improve of the accuracy of rainfall intensity observed by weather radar and microwave radiometer carried on satellite, the information on the vertical profile of raindrop size distribution (DSD) is important. The purpose of this study is to make clear the vertical profile of DSD by using 400MHz-band Wind Profiler (400MHz WPR). Two distinct peaks of Doppler spectrum of air motion and precipitation are observed by 400MHz WPR. In the case of Doppler spectrum of air motion and precipitation can be divided from observed Doppler spectrum, DSD is derived using by the Kobayashi's algorithm. Kobayashi's algorithm estimate directly DSD from Doppler spectrum of precipitation. An observed Doppler spectrum is a convolution of Doppler spectrum of the air motion and precipitation.Doppler spectrum of air motion is assumed to have a Gaussian distribution. Spectral width and vertical air velocity of parameters of Gaussian distribution are determined by the least square method. In the case of observed Doppler spectrum of air motion is small vertical air velocity in and above melting layer in stratiform rainfall, Doppler spectrum of air motion and precipitation cannot be divided from observed Doppler spectrum. In this study, DSD is estimated by using new algorithm in and above melting layer in stratiform rainfall. First step, vertical air velocity and spectral width of parameters of Gaussian distribution are assumed to be zero. Namely, Doppler spectrum of precipitation equal to observed Doppler spectrum, and DSD is estimated from observed Doppler spectrum. Second step, radar reflectivity is calculated from DSD. Third step, comparing with radar reflectivity of COBRA and 400MHz WPR, vertical air velocity and spectral width of parameters of Gaussian distribution are determined by using the least square method that radar reflectivity of 400MHz WPR become equal with radar reflectivity of COBRA. Finale step, DSD is estimated from Doppler spectrum of air motion and precipitation. Vertical characteristics of raindrop size distribution will be presented.