资源环境科技发展态势分析平台

Four years (April 2014 to March 2018) of Global Precipitation Measurement (GPM) Precipitation Features data along with colocated the Modern Era Retrospective-Analysis for Research and Applications-2 model data are used to identify Freezing Rain Features (FRFs). A Precipitation Feature with presence of both melting layer (maximum temperature of the vertical column > 4 degrees C) and a layer of subfreezing air (2-m temperature < 0 degrees C) adjacent to the surface is considered an FRF. During 4 years of observations, GPM and Modern Era Retrospective-Analysis for Research and Applications-2 identify approximately 3,096 FRFs globally (65 degrees S-65 degrees N). Most of them are observed over Northern Hemispheric land in the winter season. The majority of FRFs originates through the "melting process," whereas only 35 features are associated with "warm rain" process. The locations and seasonal and diurnal distribution patterns of the FRFs over the United States are well matched with the ground-based observations. The ground-based observations verify approximately 70% of the FRFs over the United States. Ku-band radar properties show that FRFs are found shallower (2-5 km) and less intense (<27 dBZ) than precipitation features in general but deeper and more intense than Snow Features. Passive microwave properties show that FRFs Tbs and Polarization-Corrected Temperature are warmer than Snow Features at all GPM Microwave Imager channels with the largest differences in 166 GHz. The enhancement in Tbs are more distinct with warm rain FRFs. FRF Tb tends to decrease as echo top height increases at all GPM Microwave Imager channels except for 183 GHz, where Tbs have lack of dependence on echo top height.