Retrieval of Vertical Profiles of Liquid Water and Ice Content in Mixed Clouds from Doppler Radar and Microwave Radiometer Measurements

摘要

A new method to retrieve vertical profiles of liquid water content M_w (z). ice water content M_i (r). and ice panicle size distribution N_i (D, z) (where D is the ice particle size and z the vertical coordinate) in mixed nonprecipitating clouds usingthe observations of a zenith-viewing Doppler radar and of a microwave radiometer is proposed. In this method, the profile of the vertical air velocity deduced from Doppler radar measurements is used to describe the rate of production by the updrafts ofwater vapor in excess of saturation with respect to ice. Using a Z_i-M_i power-law relation with an unknown linear parameter (let a, be this parameter) and initially assuming that Z_i is negligible with respect to Z_i (where Z_w and Z_i are the radar reflectivity factors of liquid water and ice particles, respectively), the measured radar reflectivity factor profile Z_m (approx = Z_i) is inverted to estimate N_i (D, z). From N_i (D, z). the profile of the rate of water vapor that can be consumed by puredeposition on ice particles is calculated. The difference between the rate of production of the excess water vapor and the rate of deposited water vapor is an expression of the rate of liquid water generation at each level. By writing that the integralof the liquid water along the profile has to be equal to the total liquid water deduced from the microwave radiometer measurement, an estimation of the a, parameter is obtained. From α_i an estimation of the profiles M-w (z), M_i (z), Z_w (z), Z_i (z) (= Z_m - Z_w), and N_i(D, z) is calculated. If Z_w is effectively negligible with respect to Z_i the computation of the retrieved profiles is ended. If not, Z_i (z) is corrected and a new estimation of the profiles is computed. The results of the numerical simulation of the algorithm are presented.