机载W波段测云雷达回波强度衰减订正仿真研究

Simulation Study on the Attenuation Correction to Reflectivity Factor Observed with an Air-Borne W-Band Cloud Radar

考虑到大气和云对W波段雷达波的衰减,数值仿真4种非降水云的机载W波段雷达(94GHz,3.2 mm)回波强度;基于雷达回波强度Z与云衰减系数k之间的经验关系,进行雷达回波衰减订正。结果表明,在云厚、云滴粒子浓度和含水量参数的一般取值情况下,可以获得比较好(相对误差<15%)的订正效果。随着云体加厚、云中大滴增多和含水量增加,云体对雷达回波的衰减增强,透过率降低,雷达测量值偏离真实值的程度增大,云下部衰减订正难度加大。雷达测量误差会对衰减订正效果造成一定影响。与常规测雨天气雷达回波的雨区衰减订正相比,定性来说是一致的。

Radar reflectivity factors observed with an air-borne W-band cloud radar（94 GHz,3.2 mm） numerically simulated for four typical non-precipitating clouds with different thicknesses,liquid water content and cloud-drop particle density and echo intensity correction for attenuation caused by cloud droplets and atmospheric gases have been studied,based on the generalized relationship of cloud attenuation coefficient and radar reflectivity factor.The results show that the algorithm for attenuation correction works quite well（relative error less than 15%） for typical cases determined by cloud thickness,liquid water content and cloud-drop particle density.As either of parameters such as the cloud thickness,the number of larger droplets and liquid water content increases,the transmittance decreases and the difference between the observed echo intensity and true reflectivity factor increases,leading to the increase of the difficulty in the attenuation correction for the deeper part of the cloud.Besides,the random measurement errors in radar observations also have certain influences on attenuation correction results.