夏季西太平洋暖池热含量对华西秋雨的影响及可能的物理机制

Impacts of the summertime warm pool in the West Pacific on Huaxi autumn rain and its possible physical mechanism

中文关键词:  华西秋雨  暖池  热含量

英文关键词:Huaxi autumn rainfall  Warm pool  Heat content

中文摘要:

      利用1971—2012年气象台站逐日资料，综合考虑降水量、降水日数及日照时数计算华西秋雨强度，结合不同深度海温资料，研究了华西秋雨强度与夏季西太平洋暖池热含量年际变化的联系，并讨论了其可能的物理机制。结果表明，前期夏季西太平洋暖池关键区（5°S—5°N，130°—160°E）热含量变化与华西秋雨强度有显著正相关关系，当前期关键区热含量偏高（低）时，华西秋雨强度较强（弱）。分析发现，当前期关键区热含量偏高时，其相对大气是一个异常热源，由于大气对其的响应，在热含量关键区西北侧中国南海—中南半岛附近生成了异常气旋式环流，其偏东偏南气流有利于向华西地区输送中低纬度洋面上大量暖湿水汽，并与北方的干冷空气在此交汇，同时，高层西风急流异常西伸，华西地区恰好位于急流入口区右侧的辐散区，这种高、低层有利的耦合形势使得秋雨偏强，反之亦然。

英文摘要:

      Stations daily observations including precipitation, rainfall days and sunshine time are combined with sea surface temperature (SST) at different depths to study the relationship between Huaxi autumn rain intensity and summertime heat content in the western Pacific warm pool. The possible physical mechanism is also discussed. Results show that in summer, the variation of heat content in the western Pacific warm pool key area (5°S-5°N, 130°-160°E) is significantly positively correlated with the intensity of Huaxi autumn rain. When the heat content is high (low) over the key area, the intensity of Huaxi autumn rain is strong (weak). Further analysis reveals that when the heat content in the key area is high, it is like an abnormal heat source that leads to abnormal cyclonic circulation near the South China Sea-Indo-China Peninsula to the northwest of the key area. The southerly and easterly flows associated with the cyclonic anomaly are favorable for moisture transport to Huaxi, where the warm, moist airmass converges with dry, cold airmass from the north. Meanwhile, the upper-level westerly jet extends westward abnormally, leading to divergence above Huaxi, which is located to the right of the westerly jet entrance. The coupling between upper and lower circulations results in strong rain in Huaxi, and vice versa.