Improved Hydrometeor Detection Method: An Application to CloudSat
Improved Hydrometeor Detection Method: An Application to CloudSat
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DOI：
10.1029/2019ea000900
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发表时间：
2020-02
影响因子：
3.1
通讯作者：
Xiaoyu Hu;J. Ge;Yanrong Li;R. Marchand;Jianping Huang;Q. Fu
中科院分区：
文献类型：
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作者：
Xiaoyu Hu;J. Ge;Yanrong Li;R. Marchand;Jianping Huang;Q. Fu
云在气候系统中发挥着重要作用，也是气候预测不确定性的主要来源。 CloudSat为研究云的垂直结构提供了前所未有的机会，其观测结果正在广泛应用于科学研究。然而，有些云未被 CloudSat 检测到或仅微弱地检测到。在大多数研究中，最弱的检测，特别是通过所谓的沿轨积分方案检测到的检测，通常会被忽略，因为错误检测率很高，即检测到的云实际上很可能是测量噪声增加的区域，而不是真正的云信号。 CloudSat 云掩模产品的最新版本（版本 5 称为 R05）中的错误检测已减少，但代价是真实的弱信号显着丢失（即较高的错误遗漏率）。本研究对R05中使用的CloudSat水凝物检测算法进行了修改，添加了双边滤波方案，以改善对微弱信号的检测。通过与CALIPSO激光雷达垂直特征掩模的比较表明，新方案与R04版本相比大大降低了误检率，同时保留了R05版本中丢失的很大一部分真实的微弱信号。在未来的 CloudSat 数据处理中实施该方案预计将能够更好地检测薄云。
Clouds play an important role in the climate system and are a principal source of uncertainty in climate projections. CloudSat has provided an unprecedented opportunity to study the vertical structure of clouds, and its observations are being widely used in scientific studies. However, some clouds are not detected or are only weakly detected by CloudSat. In most studies, the weakest detections, specifically those detected by the so‐called along‐track integration scheme, are typically ignored due to the high rate of false detections, namely, a significant probability that a detected cloud is actually a region of increased measurement noise, rather than a true cloud signal. False detections have been reduced in the latest version (called R05 for release 5) of the CloudSat cloud mask product but at a cost of a significant loss in the true weak signals (i.e., a higher false omission rate). In this study, the CloudSat hydrometeor detection algorithm used in R05 is modified by adding a bilateral filter scheme to improve the detection of weak signals. By comparing with the CALIPSO lidar vertical feature mask, it is shown that the new scheme largely reduces the false detection rate compared to the R04 version, while retaining a large fraction of the true weak signals that have been lost in the R05 version. Implementing this scheme in future CloudSat data processing is expected to lead to a better detection of thin clouds.