Retrieval of raindrop size distributions from the L-band and VHF wind profilers during convective and stratiform rain

185-196 A new approach is proposed to retrieve the rain drop size distribution (RDSD) by the combined use of velocity spectra of L–band and VHF wind profilers by taking into account of updrafts/downdrafts. The corrected velocity spectra during rain are fitted with the lognormal functional form by using the Marquerdt-Levenberg algorithm. The corrected velocity spectrum of the L-band profiler is converted to RDSD spectrum. On 22-23 June 2000, for convective and stratiform rain, the retrieved rain integral parameters from the wind profilers are compared with Joss-Waldovegel Disdrometer (JWD) measurements. Reasonably good agreement is found between the observations from these two systems, when the updrafts/downdrafts corrections are applied. During the convective rain, for rain rate, the root mean square (rmse) and correlation coefficients are found to be 5.0 mm/h and 0.74, respectively and for mean rain drop diameter (Dm) the rmse and correlation coefficient are 0.66 mm and 0.58. Similarly during stratiform rain, rmse and correlation coefficients for rain rate are found to be 1.01 mm/h and 0.71. For Dm, the rmse and correlation coefficient are 0.67 mm and 0.65, respectively. An inverse relationship is observed between profiler derived total number of drops (Nt) and Dm.