Observation of cirrus clouds with GLORIA during the WISE campaign: detection methods and cirrus characterization
Observation of cirrus clouds with GLORIA during the WISE campaign: detection methods and cirrus characterization
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DOI：
10.5194/amt-14-3153-2021
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发表时间：
2021-04
影响因子：
3.8
通讯作者：
Irene Bartolome Garcia;R. Spang;J. Ungermann;S. Griessbach;M. Krämer;M. Höpfner;M. Riese
中科院分区：
文献类型：
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作者：
Irene Bartolome Garcia;R. Spang;J. Ungermann;S. Griessbach;M. Krämer;M. Höpfner;M. Riese
抽象。卷云对地球的总辐射收支有贡献，在气候预测中发挥重要作用。特别令人感兴趣的是靠近对流层顶的光学薄卷云，因为它们的影响还没有得到很好的理解。测量这些云是具有挑战性的，因为需要高空间分辨率以及非常高的检测灵敏度。满足这些标准的是红外临边探测格洛丽亚（用于大气辐射成像的万向架临边观测器）。这项研究使用格洛丽亚在2017年9月和10月的WISE（波浪驱动等熵交换）活动期间在德国研究飞机HALO上获得的数据对观测到的卷云进行了表征。我们开发了一种基于云指数和在微窗832.4-834.4 cm−1处检索的消光系数的优化云检测方法。我们推导出探测到的卷云的宏观物理特征，如云顶高度，云底高度，垂直范围和云顶相对于对流层顶的位置。在对流层顶上方探测到的卷云的比例约为13%至27%。在一般情况下，良好的协议与ERA 5再分析数据集预测的云。然而，在靠近对流层顶和对流层顶以上的地区的观测中，云的出现率要高出约50%。对流层顶上方的云底高度也被探测到。然而，考虑到不确定性，我们不能确认对流层顶上方形成独立的卷云层。
Abstract. Cirrus clouds contribute to the general radiation budget of the Earth and play an important role in climate projections. Of special interest are optically thin cirrus clouds close to the tropopause due to the fact that their impact is not yet well understood. Measuring these clouds is challenging as both high spatial resolution as well as a very high detection sensitivity are needed. These criteria are fulfilled by the infrared limb sounder GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere). This study presents a characterization of observed cirrus clouds using the data obtained by GLORIA aboard the German research aircraft HALO during the WISE (Wave-driven ISentropic Exchange) campaign in September and October 2017. We developed an optimized cloud detection method based on the cloud index and the extinction coefficient retrieved at the microwindow 832.4–834.4 cm−1 . We derived macro-physical characteristics of the detected cirrus clouds such as cloud top height, cloud bottom height, vertical extent and cloud top position with respect to the tropopause. The fraction of cirrus clouds detected above the tropopause is on the order of 13 % to 27 %. In general, good agreement with the clouds predicted by the ERA5 reanalysis dataset is obtained. However, cloud occurrence is ≈ 50 % higher in the observations for the region close to and above the tropopause. Cloud bottom heights are also detected above the tropopause. However, considering the uncertainties, we cannot confirm the formation of unattached cirrus layers above the tropopause.