摘要:全球测雨卫星（GPM）携带首部Ka和Ku波段测雨雷达于2014年2月发射升空，继热带测雨卫星（TRMM）的单频测雨雷达探测后，实现双频测雨雷达（DPR）探测。本文基于DPR不同波段及不同方式探测反演给出的四种降水产品[Ka波段高精度探测（KaHS）、Ku波段探测（KuPR）、Ka匹配方式探测（KaMS）和Ka及Ku双频联合探测反演产品（DPR_MS）]，对2014年的四个降水个例的降水结构特征进行了分析，并就DPR探测波段、扫描方式及反演算法所引起的降水产品中降水结构特征差异进行了比较与讨论。结果表明，所选四个个例分别位于中国东部、西北太平洋区域、风暴轴区域以及美国本土，四者发生背景及降水特征差异显著，但表现出了较为一致的产品差异特征。KaHS的回波顶高度最高，比KuPR高约0.1 km，其对弱降水（小于0.5 mm h-1）的观测性能好，但对10 mm h-1以上的强降水存在严重低估。KuPR继承了TRMM测雨雷达（PR）对强降水的观测性能，但受频率限制对0.5 mm h-1以下的弱降水观测能力有限。KaMS的整体降水强度分布与KaHS类似，但受高回波阈值限制，KaMS漏掉了大量弱降水样本，对强弱降水的观测性能均有限，且其平均回波顶高度比KuPR可低约1 km，常将融化层误判为回波顶高度，故不适宜单独使用。DPR_MS的降水反演算法具有独立性，对强降水和弱降水的反演能力都较强，而其回波顶高度主要继承于KuPR的回波顶高度。此外，DPR_MS双频反演的粒子谱最为合理，揭示了西北太平洋区域台风个例两侧眼壁粒子谱的不均匀性。
关键词:GPM卫星/
双波段探测/
降水结构/
粒子谱分布
Abstract:The GPM (Global Precipitation Measurement) satellite carrying the first Ka-and Ku-band precipitation radar was launched in February 2014.GPM realized the DPR (Dual-frequency Precipitation Radar) detection following TRMM's (Tropical Rainfall Measurement Mission) PR (Precipitation Radar).Based on the four precipitation products provided by DPR including KaHS (Ka-band high-sensitivity product), KuPR (Ku-band product), KaMS (Ka-band matched product), and DPR_MS (dual-frequency product), structural features of four selected precipitation cases occurred in 2014 are analyzed.The structural differences caused by detecting frequencies, scan modes, and retrieval methods are then compared and discussed.The results show that the four selected precipitation cases occurred in East China, the northwestern Pacific, the storm track area, and the United States, respectively.Although the background environment and precipitation characteristics of the four cases are significantly different, some consistent differences among these products are revealed by the study of these cases.KaHS presents the highest storm top height, which is 0.1 km higher than that from KuPR.KaHS shows great advantages in observing precipitations weaker than 0.5 mm h-1.However, KaHS underestimates precipitation intensities larger than 10 mm h-1.KuPR inherits the good performance of TRMM PR for intense precipitation observations, and presents the largest proportion of precipitation higher than 10 mm h-1.But KuPR is not suitable for observing precipitations weaker than 0.5 mm h-1 due to its operating frequency.KaMS's near surface rain rate is similar to that of KaMS except that KaMS omits large number of weak precipitation (limited by the minimum echo threshold).Thus KaMS is not good at observing both intense and weak precipitation and not appropriate to be used independently.The precipitation retrieval algorithm of DPR_MS is highly self-governed and performs well in retrieving both weak and intense precipitations, while DPR_MS's storm top height strongly relies on KuPR's with the correlation coefficient close to 1.In addition, the droplet size distribution retrieved by DPR_MS is most reasonable and can well reveal the nonuniformity on the two sides of the typhoon eye wall.
Key words:GPM (Global Precipitation Measurement) satellite/
Dual-frequency observation/
Precipitation structure/
Droplet size distribution
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