| 两类季风槽特征及海南岛的强降水机制 |
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| 引用本文： | 陈红,郭冬艳,吴俞,李勋.两类季风槽特征及海南岛的强降水机制[J].热带生物学报,2022,13(4):348-357. |
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| 作者姓名： | 陈红 郭冬艳 吴俞 李勋 |
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| 作者单位： | 海南省气象台，海口 570203 |
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| 基金项目： | 海南省科学技术厅省自然科学基金项目（20154183） |
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| 摘 要： | 为了提高海南季风槽暴雨预报水平，深入了解南海季风槽天气气候特征及其对强降水形成的影响，提高海南季风槽暴雨预报水平，利用NCEP再分析资料(1°×1°)及海南岛降水资料，统计分析了2001—2020年的5—9月205次南海季风槽活动及海南岛强降水（3站以上暴雨）过程的时空分布特征，季风槽位置按分为两类（Ⅰ、Ⅱ类），分别对其强降水过程的高低空环流形势场和物理量场进行多样本合成对比分析。结果表明:(1)影响海南的季风槽过程年均出现10.3次，年均58.4 d，一次过程平均5.7 d,其中强降水占7.1%,主要发生在8月和9月,Ⅰ类季风槽在8月最活跃，9月最易产生强降水，Ⅱ类季风槽最活跃和强降水占比最高的月份均为9月，两类强降水的暴雨高频区分布差异较大，Ⅱ类更容易出现极端降水。（2）高层南亚高压的辐散作用、中低层强盛的季风和季风槽是发生强降水的前提，但季风槽位置不同导致影响降水的系统配置有区别。Ⅰ类强降水的发生与季风槽切变线位置、结构密切相关，季风将水汽和能量向槽区输送，季风槽低层辐合、高层辐散的配置特征使低层的对流和上升运动得以建立和加强从而产生降水，暴雨高频区与切变线南侧、气旋式环流右侧辐合条件最强的区域对应；Ⅱ类则与季风槽北侧低空急流有关，低层水汽和能量通过低空急流向位于急流左前方的海南岛输送，并在海南岛产生强烈的辐合上升运动，导致强降水发生。（3）降水强弱分布与海南岛钟状特殊地形结构也有紧密联系，两类季风槽暴雨高频区均与地形强作用区有很好的对应，但由于低层背景风不同，二者存在明显差别。
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| 关 键 词： | 季风槽 强降水 环流特征 低空急流 |
| 收稿时间： | 2021-09-15 |
Analysis of the characteristics of two different types of monsoon trough and mechanisms of heavy rainfall over Hainan Island |
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| Institution: | Hainan Meteorological Station, Haikou 570203 |
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| Abstract: | The spatial and temporal distribution characteristics for South China Sea monsoon trough activities and heavy rainfall between May to September from 2001 to 2020 Hainan Island were statistically analyzed by using NCEP reanalysis and land-based observations in Hainan Island. Monsoon trough that generates heavy rainfall events were grouped into two types according to its position. The composite analysis of high- and low-level circulations and their element fields were performed. The results show that the monsoon trough affecting Hainan occurred about 10.3 times per year on average, 58.4 days per year, and 5.7 days per event on average. The heavy rainfall events accounted for 7.1%, mainly occurring in August and September. The first type of monsoon trough was mostly active in August, and was the easiest to bring heavy rainfall in September. The second type of monsoon trough was mostly active in September and brought heavy rainfall most frequently in September as well. The high frequency heavy rainfall zones generated from the first and second types of monsoon trough were different, and the second type of monsoon trough tended to bring heavy rainfall more easily. The divergence of the high-level South Asia high, and strong monsoon and monsoon trough on moderately low level were a prerequisite for the occurrence of heavy rainfall, but establishment of monsoon trough at different locations led to different system configurations of rainfall. The occurrence of heavy rainfall in the first type of monsoon trough was highly related to the structure and shear line location of monsoon trough. The monsoon transferred the water vapor and energy to the trough zone, and the convergence on the low level and the divergence on the high level of monsoon trough generated and enhanced the convection and ascending motion on low level, which led to heavy rainfall. The high frequency heavy rainfall area in the first type of monsoon trough corresponded to the strongest convergence area on the south of the trough and the right side of cyclone circulation. The occurrence of heavy rainfall in the second type of monsoon trough was related to the low-level jetstream on the north side of monsoon trough and the water vapor and energy on low level were transferred by low-level jet to Hainan Island and resulted in the intense convergence upward motion over the island, which led to the occurrence of heavy rainfall. The intensity distribution of rainfall was also highly related with the special bell-shaped terrain of Hainan Island. The high frequency heavy rainfall areas in the two types of monsoon trough were both well corresponding to the strong terrain effect area, but were obviously different due to the different low wind background on low level. |
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