机载毫米波雷达反演降水性积层混合云暖区液态水含量及其与飞机观测的对比

Retrieval of liquid water content in warm precipitating stratiform-convective clouds from airborne millimeter-wavelength radar and comparison with aircraft observations

液态水含量(Liquid Water Content,LWC)是重要的云参数,对了解云微物理过程以及在人工影响天气效果检验等方面有重要的指导意义。针对已有研究的反射率因子(Z)与LWC经验公式适用范围有限的问题,利用2018—2020年飞机观测资料,在验证中国首部机载云雷达(Ka-band Precipitation Radar,KPR)探测能力和数据可靠性的基础上,采用分档平均方案,建立了适用于降水性积层混合云的Z-LWC经验公式(Z=2454.71×LWC^(1.614)),决定系数达0.995,均方根误差(RMSE)为0.2 g/m^(3)。验证表明,该经验公式反演的液态水含量与飞机实测的LWC吻合较好,且在大多数情况下都优于已有经验公式反演的结果。

Liquid Water Content(LWC)is a key variable of clouds and has great implication for understanding cloud microphysical processes and validating weather modification.However,the application of relationships between reflectivity(Z)and LWC proposed in previous studies is limited.In this study,the reliability of the airborne Ka-band millimeter wavelength cloud radar(Ka-band Precipitation Radar,KPR)and cloud particle detection instruments are validated first.Cloud data collected by the radar and the particle instrument onboard airplane during 2018—2020 are then processed and smoothed within different cloud diameter ranges and radar reflectivity ranges to build a new Z-LWC relationship suitable for precipitating stratiform-convective cloud.The new relationship is(Z=2454.71×LWC^(1.614)),with determination coefficient of 0.995 and root mean squared error(RMSE)is 0.2 g/m^(3).Verification shows that the retrieved LWC is consistent with the measurements by the cloud particle detection instruments,and the discrepancy between the retrieval and observations is smaller than that between retrievals by other Z-LWC relationships and observations.