Terrain‐Enhanced Precipitation Processes Above the Melting Layer: Results From OLYMPEX
Terrain‐Enhanced Precipitation Processes Above the Melting Layer: Results From OLYMPEX
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DOI：
10.1029/2018jd029161
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发表时间：
2018-11
期刊：
影响因子：
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通讯作者：
L. McMurdie;A. Rowe;R. Houze;R. Houze;S. Brodzik;Joseph P. Zagrodnik;T. M. Schuldt
中科院分区：
文献类型：
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作者：
L. McMurdie;A. Rowe;R. Houze;R. Houze;S. Brodzik;Joseph P. Zagrodnik;T. M. Schuldt
利用在奥林匹克山脉实验期间部署在华盛顿州西海岸的S波段扫描雷达的反射率数据，记录了复杂地形上高空降水过程的增强。从2015年11月到2016年1月中旬，NPOL获得了海洋上空和奥林匹克山脉迎风坡面上的高分辨率数据。雷达反射率的等高线频率图突出表明，与海洋相比，陆地上空2至8公里所有高度的反射率较大的频率更高，其中4至6公里范围内的差异最大，表明迎风斜坡上空的增强具有很强的特征。在所考虑的所有环境条件下，这种增强模式都在一定程度上被发现，但在高水汽输送、高融化高度、西南低层风和中性稳定期尤其明显。这些情况通常与中纬度气旋和大气河流的温暖部分有关。过去的研究假设，高空反射率的二次增强是大气河流类型系统的固有部分。然而，这些结果表明，当深水湿中性、高水汽含量的气流在遇到山脉时被抬升时，这种特征会进一步显著增强。全球降水测量卫星上的双降水雷达的反射率数据也记录了与邻近海洋相比，奥林匹克山脉上空的反射率增加，这表明全球降水测量有潜力对偏远山区的降水结构提供可靠的估计。
Enhancement of precipitation processes aloft over complex terrain is documented using reflectivity data from an S‐band scanning radar (NPOL) that was deployed on the west coast of Washington State during the Olympic Mountains Experiment (OLYMPEX). From November 2015 through mid‐January 2016, NPOL obtained high‐resolution data within sectors over the ocean and over the windward slopes of the Olympic Mountains. Contoured Frequency by Altitude Diagrams of radar reflectivity highlight a higher frequency of occurrence of larger reflectivities for all heights between 2 and 8 km over land compared to ocean, with the largest difference in the 4‐ to 6‐km range indicating a robust signature of enhancement aloft over the windward slopes. This enhancement pattern is found to some degree under all environmental conditions considered but is especially pronounced during periods of high vapor transport, high melting level height, southwest low‐level winds, and neutral stability. These conditions are generally associated with warm sectors of midlatitude cyclones and atmospheric rivers. Past studies have postulated that a secondary enhancement in reflectivity aloft was an intrinsic part of atmospheric river type systems. However, these results show that further significant enhancement of this signature occurs as deep moist‐neutral, high water vapor content flow is lifted when it encounters a mountain range. Reflectivity data from the dual‐precipitation radar aboard the Global Precipitation Measurement satellite also documents this reflectivity increase aloft over the Olympic Mountains compared to the adjacent ocean, showing the potential for Global Precipitation Measurement to provide reliable estimates of precipitation structure over remote mountainous regions.