江南雨季降水与前期西太平洋暖池热含量异常的关系及其可能机制
投稿时间: 2016-03-10  最后修改时间: 2016-07-29  点此下载全文
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作者单位E-mail
任倩 中国气象局成都高原气象研究所高原与盆地暴雨旱涝灾害四川省重点实验室 renqiannxd@163.com 
祁莉 南京信息工程大学大气科学学院 qili@nuist.edu.cn 
詹丰兴 江西省气象局  
何金海 南京信息工程大学大气科学学院  
基金项目:国家重点基础研究发展计划(973计划);国家自然科学基金项目(面上项目,重点项目,重大项目)
中文摘要:利用日本气象厅提供的历史海温资料、Hadley环流中心逐月海表温度资料、美国NCEP/NCAR再分析资料以及江南地区逐旬降水资料,探讨了江南地区4-6月(江南雨季,亦泛称为华南前汛期)降水与前期暖池热含量异常的关系,并对可能的影响机制进行了分析。研究结果表明,前期暖池热含量与江南雨季降水有密切的负相关关系,前期7-8月暖池关键区(3.5°N -11.5°N,130.5°E -150.5°E)热含量高(低)可以作为预报江南雨季旱(涝)的一个很好的指标。前期暖池热含量异常对4-6月环流和降水有重要的影响。冷水年,菲律宾异常反气旋导致副高西伸加强,显著加强了其西侧暖湿气流向江南地区输送,高层辐散抽吸作用导致江南地区对流上升运动增强,暖水年相反,表明冷(暖)水年江南雨季降水偏多(少)。就影响机制而言,在前期夏季,关键区南侧存在异常强西风,导致在秋末形成了菲律宾异常反气旋,以及关键区附近(东侧)有冷(暖)海表温度异常发展,在当年春季和夏初该反气旋移到菲律宾以北。直到4月,次表层冷水团上传导致冷SSTA维持并加强了该异常反气旋,其西侧西南暖湿气流将水汽从南海和菲律宾海地区源源不断地向江南地区输送。同时,西印度洋暖海温和赤道印度洋东风异常也逐渐发展增强,在热带印度洋形成东西向异常垂直环流,其下沉支始终在西太平洋维持,导致了菲律宾异常反气旋的维持,并进一步引起江南地区的水汽辐合和上升运动。同时,副热带西风急流轴南压引起的高空强辐散也有利于上升运动和对流活动在江南地区发展。正是上述过程和机制,导致了前期热含量异常偏低(高)时,我国江南雨季降水偏多(少)。
中文关键词:西太平洋暖池  热含量  江南雨季  菲律宾反气旋  对流上升运动
 
Relationship between Precipitation in Jiangnan Rainy Season and Preceding Heat Content Anomaly over Western Pacific Warm Pool and Its Possible Mechanism
Abstract:By using the historical SST data provided by Japan Meteorological Agency and Hadley center, NCEP / NCAR reanalysis data, and the ten day precipitation in Jiangnan, the relationship between Jiangnan precipitation from April to June (Jiangnan rainy season, which is also called the first flood period in South China) and the preceding heat content anomalies over western Pacific warm pool and its possible mechanism are studied. The results show that precipitation in Jiangnan rainy season is negatively related to the heat content anomalies over the warm pool. The heat content over the key area (3.5 ° N-11.5 ° N, 130.5 ° E-150.5 °E) in July and August could be regarded as a good precursor of the winter rainfall. The preceding heat content has an important influence on precipitation and circulation from April to June. In cold years, the anomalous Philippines anticyclone intensifies the western extension of Subtropical High, strengthening the transportation of warm and wet flow from west side of anticyclone to Jiangnan, and with divergence in upper troposphere, the anomalous convective rising motion enhances in Jiangnan and vice versa. It indicates that the precipitation in Jiangnan rainy season is more (less) in cold (warm) years. When it comes to the mechanism. the strong westerly anomalies to the south of key area in previous summer results in the development of an anomalous Philippines anticyclone in late autumn and cold (warm) SST to the west (east) of key area. Until April, the upwelling of subsurface cold water sustains cold SSTA and enhances the anticyclone, which continuously transports water vapor to Jiangnan. Meanwhile, the anomalous zonal vertical circulation enhances in the tropic Indian with the development of warm SST in the western Indian and easterly anomalies in the equator. Its sinking branch in the western Pacific sustains the anomalous anticyclone, which further induces the water vapor convergence and rising motion in Jiangnan. Moreover, upper strong divergence induced by southward moving of the subtropical westerly jet also favors the increasing convective rising motion in Jiangnan. It is the above processes that lead to more (less) rainfall in Jiangnan rainy season with the preceding negative (positive) heat content anomalies over the key area.
keywords:Western Pacific warm pool  Heat content  Jiangnan rainy season  Philippines anticyclone  Convective rising motion
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