Satellite Observations of Reflectivity Maxima above the Freezing Level Induced by Terrain
Satellite Observations of Reflectivity Maxima above the Freezing Level Induced by Terrain
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DOI：
10.1007/s00376-020-0221-5
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发表时间：
2021-02
影响因子：
5.8
通讯作者：
A. Zhang;Weibiao Li;Shumin Chen;Yilun Chen;Yunfei Fu
中科院分区：
文献类型：
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作者：
A. Zhang;Weibiao Li;Shumin Chen;Yilun Chen;Yunfei Fu
以前的研究已经认识到山坡上层状降水的最大反射率高于冰冻水平(RMAF)，然而，由于缺乏足够的识别标准，定量研究有限。在这里，我们建立了一种识别RMAF降水的方法，并将其应用于热带降雨测量任务(TRMM)降水雷达(PR)的观测。使用1998-2013年的TRMM 2A25产品，我们表明可以有效地识别反射率分布中的RMAF结构。RMAF不仅存在于层状降水中，也存在于对流降水中。RMAF频率与海拔高度呈正相关，这被认为是由于层状降水的中层或山区对流性降水的中低层的上升气流增强所致。层状降水和对流降水的平均RMAF高度分别在冰冻高度上方1.35和2.01公里，低于前人的结果。此外，我们的结果表明，RMAF结构增加了回波顶高度，增强了RMAF高度以上的降水过程，但抑制了冰粒的向下传播和近地面降雨率。今后对地形降水的研究应考虑到RMAF结构及其相关动力触发因素的影响。
Previous studies have recognized reflectivity maxima above the freezing level (RMAF) within stratiform precipitation over mountain slopes, however, quantitative studies are limited due to the lack of adequate identification criteria. Here, we establish an identification method for RMAF precipitation and apply it to the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) observations. Using the TRMM 2A25 product from 1998 to 2013, we show that the RMAF structure in reflectivity profiles can be effectively identified. RMAF exists not only in stratiform precipitation but also in convective precipitation. RMAF frequency is positively correlated with elevation, which is thought to be caused by enhanced updrafts in the middle layers of stratiform precipitation, or in the low to middle layers of convective precipitation over mountains. The average RMAF heights in stratiform and convective precipitation were 1.35 and 2.01 km above the freezing level, respectively, which is lower than previous results. In addition, our results indicate that the RMAF structure increased the echo top height and enhanced precipitation processes above the RMAF height, but it suppressed the downward propagation of ice particles and the near-surface rain rate. Future studies of orographic precipitation should take into account the impact of the RMAF structure and its relevant dynamic triggers.