Characteristics of Coastal Low-Level Jets Over Beibu Gulf, China, During the Early Warm Season
Characteristics of Coastal Low-Level Jets Over Beibu Gulf, China, During the Early Warm Season
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暖季初期中国北部湾沿岸低空急流特征
DOI：
10.1029/2019jd031918
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发表时间：
2020
影响因子：
4.4
通讯作者：
Zhang Fan
中科院分区：
文献类型：
--
作者：
Kong Hoiio;Zhang Qinghong;Du Yu;Zhang Fan
我们调查了沿海低空急流（CLLJs），中国北部湾，在温暖的季节（5月至7月），使用逐小时模式模拟中尺度天气研究和预报模式与9公里的水平分辨率。在北部湾上空发现了两个CLLJ高发区：一个位于日落后盛行的安南山脉的背风侧，另一个位于海南岛西北海岸，午夜达到最大强度。由于印度支那陆面附近强烈的湍流混合，安纳米特山脉的上游风在白天太弱而无法通过该山脉;但由于日落后湍流混合的抑制，气流增强并越过安纳米特山脉，并进一步在下游形成水力跃射流。除了上游的平流作用外，海南岛的地形阻塞作用也对海南岛西北部近海的CLLJ有一定的贡献，该CLLJ在白天持续存在，但在午夜变得更加普遍。进一步的动量收支分析和敏感性实验表明，陆地湍流日变化引起的上游惯性振荡是海洋CLLJ的主要来源。这些发现揭示了北部湾CLLJ的主要机制，为其他沿海复杂山脉地区CLLJ的形成提供了见解。
We investigated coastal low-level jets (CLLJs) over Beibu Gulf, China, during the warm season (May to July) using hourly model simulations from a mesoscale weather research and forecasting model with a 9-km horizontal resolution. Two high-incidence CLLJ areas were identified over Beibu Gulf: one located on the leeward side of the Annamite Range that prevailed after sunset and the second off the northwestern coast of Hainan Island that reached its maximum intensity at midnight. The upstream wind of the Annamite Range was too weak to pass over the range during the daytime due to strong turbulent mixing near the land surface of Indochina; however, due to the suppression of the turbulent mixing after sunset, the flow intensified and crossed over the Annamite Range and further formed a hydraulic jump jet downstream. In addition to advection effect from upstream, topographic blocking effect of Hainan Island contributed to the CLLJ off the northwestern coast of Hainan Island, which persisted during the day but became more prevalent at midnight. Further momentum budget analysis and sensitivity experiments indicated that the upstream inertial oscillation due to the diurnal variation in turbulence over land was the primary source of the CLLJ over the ocean. These findings reveal the primary mechanism of CLLJs over Beibu Gulf, providing insight into CLLJ formation in other coastal regions with complex mountain ranges.