云滴/冰晶谱和垂直气流是研究云在生消演变中微物理和动力过程的重要参量。目前探测手段不多,垂直指向的毫米波雷达Doppler功率谱是一个新的反演云滴/冰晶谱和垂直风速的有效途径。云滴下落末速小,因此受垂直气流的影响远大于雨滴,如何去除径向风的影响一直是反演的难点。本课题拟借鉴国际上已有的反演方法，联合雷达的偏振参量，建立一个新的适用于Rayleigh近似条件下各种尺度的云滴、毛毛雨滴、特定形状冰晶的谱分布以及垂直气流的反演方法。与国内外已有方法相比，该方法不受粒子谱谱型和粒子相态的限制，无需对垂直气流作先验的假设，具有更为广泛的适用范围和更好的拓展性。由于充分考虑了垂直气流的影响，该方法更加适合反演下落末速较小的云滴。为保证反演速度和精度，拟采用申请者已建立的一套快速优化反演算法进行求解。通过数值模拟试验以及对实测功率谱的反演，评估方法的精度和适用范围。

Cloud droplet/ice crystal size distribution and vertical air velocity are the key parameters to describe the microphysical and dynamic process during the evolution of clouds. Currently, detection methods for such parameters are quite limited, while the Doppler power spectrum of vertically pointed millimeter-wavelength radar is an effective way. Due to the small terminal velocity of cloud droplets, the influence of vertical air motion upon cloud droplets is much greater than raindrops. How to remove the effect of radial wind on Doppler power spectrum becomes a main difficulty in retrieval. Referring to the previous studies and combining the polarimetric parameters of radar, this research project will develop a new retrieval technique which is suitable to retrieve the particle size distribution of cloud droplet, drizzle droplet, ice crystal with certain shapes and vertical air motion. In this technique, there is no need to make any apriori assumption of the types of particle size distribution, the phase of particles or vertical air velocity. Thus this technique has much wider application scope and better expansibility as compared with the existing international and domestic methods. Since the effect of vertical air motion has been fully considered, this technique is more suitable for cloud droplet with small terminal velocity. A fast inverse algorithm developed by this applicant will be used to solve this nonlinear inverse problem to ensure the retrieval accuracy and speed. The retrieval accuracy and the extent of application of this technique will be estimated by numerical simulations and field tests.