The choice of ice particle model is critical for microwave remote sensing of ice clouds. Using a model-observation closure method, the global applicability of a series of single crystal and aggregate ice particle models is evaluated based on satellite-based microwave measurements from the CloudSat Cloud Profiling Radar (CPR) and the Global Precipitation Mission (GPM) Microwave Imager (GMI) high-frequency channels. The results indicate that the ice water path (IWP) retrievals from radar observations are highly dependent on the ice particle model, with the maximum difference between models exceeding a factor of 13. Although aggregate models generally perform better than single crystals, none of them can be well adapted to retrievals for all types of ice clouds on the global scale. A columnar single crystal works better for low IWP clouds, while a small block aggregate for high IWP. Consequently, a mixing scheme combining both with weighting by IWP is then proposed for global ice cloud measurements. By using this double-model mixing scheme, the simulations can well reproduce simultaneous active and passive microwave observations, regardless of the IWP. Specifically, the differences between CPR radar reflectivity simulations and observations do not exceed 0.1 dBZ, while the mean biases of brightness temperatures on all high-frequency channels of GMI are <1.5 K. This is expected to improve the retrieval accuracy of global ice clouds.

中文翻译：

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用于全球冰云测量的冰粒子模型混合方案


冰粒子模型的选择对于冰云微波遥感至关重要。使用模型观测闭合方法，根据 CloudSat 云剖面雷达 (CPR) 和全球降水任务 (GPM) 微波成像仪的卫星微波测量来评估一系列单晶和聚集冰粒模型的全球适用性（GMI）高频频道。结果表明，雷达观测的冰水路径（IWP）反演高度依赖于冰粒子模型，模型之间的最大差异超过13倍。虽然聚合模型通常比单晶模型表现更好，但它们都不能能够很好地适应全球范围内所有类型冰云的反演。柱状单晶对于低 IWP 云效果更好，而小块聚集体对于高 IWP 云效果更好。因此，提出了一种将两者与 IWP 加权相结合的混合方案，用于全球冰云测量。通过使用这种双模型混合方案，无论 IWP 如何，模拟都可以很好地重现同步主动和被动微波观测。具体来说，CPR雷达反射率模拟与观测的差异不超过0.1 dBZ，而GMI所有高频通道的亮温平均偏差为<1.5 K。这有望提高全球冰的反演精度云。