Interannual Variation of the Late Fall Rainfall in Central Vietnam
Interannual Variation of the Late Fall Rainfall in Central Vietnam
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DOI：
10.1175/jcli-d-11-00068.1
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发表时间：
2012-01-01
影响因子：
4.9
通讯作者：
Matsumoto, Jun
中科院分区：
文献类型：
--
作者：
Chen, Tsing-Chang;Tsay, Jenq-Dar;Matsumoto, Jun
越南中部的暴雨/洪涝(HRF)事件通常发生在10-11月，也就是降雨最多的季节。这一最大降雨量经历了明显的年际变化，与NOAA Nino-3.4区-Delta SST(Nino-3.4)平均海表面温度(SST)的年际变化相反，但与北纬15度的低层东风和北纬5度的西风的加强(减弱)相一致。低层纬向风的变化反映了热带南亚/东南亚热带气旋切变流对热带太平洋SST异常的加强(减弱)。由于越南中部的最大降雨量主要由HRF气旋产生，因此该地区降水的年际变化应归因于HRF气旋活动--降水气候变化的一个新视角。平均而言，每个寒冷的晚秋都会出现一个HRF气旋。HRF气旋的数量可能不是造成越南中部降水年际变化的重要因素。在寒冷的深秋期间，个别HRF气旋的降水效率在统计上几乎是温暖和正常深秋期间的两倍，是导致越南中部降水年际变化的最关键因素。进一步的水文分析表明，HRF气旋的增(减)雨效率是由区域水汽通量辐合增强(减弱)的大尺度环境气流决定的。
The heavy rainfall/flood (HRF) event in central Vietnam usually occurs in October-November, the maximum rainfall season. This rainfall maximum undergoes a distinct interannual variation, opposite the interannual variation of sea surface temperature (SST) anomalies averaged over the NOAA Nino-3.4 area-Delta SST(Nino-3.4)-but coincident with the intensification (weakening) of the low-level easterlies at 15 degrees N and westerlies at 5 degrees N. The changes of low-level zonal winds reflect the strengthening (weakening) of the tropical cyclonic shear flow in tropical South/Southeast Asia in response to the tropical Pacific SST anomalies. Because the rainfall maximum in central Vietnam is primarily produced by the HRF cyclone, the interannual rainfall variation in this region should be attributed to the HRF cyclone activity-a new perspective of the climate change in precipitation. On average, one HRF cyclone occurs in each cold late fall. The population of the HRF cyclone may not be an important factor causing the interannual rainfall variation in central Vietnam. During the cold late fall, the rain-producing efficiency of the individual HRF cyclone is statistically almost twice those during warm and normal late falls and the most crucial factor leading to the interannual rainfall variation in central Vietnam. It is shown by further hydrological analysis that the increase (decrease) of the HRF cyclone's rain-producing efficiency is determined by the large-scale environmental flow through the enhancement (weakening) of the regional convergence of water vapor flux.