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投稿时间：2015-06-15 修订日期：2016-08-17
投稿时间：2015-06-15 修订日期：2016-08-17
中文摘要: 利用常规气象观测资料、NCEP/NCAR 1°×1°的月平均再分析资料、NOAA卫星观测的OLR资料和中国气象局台风年鉴资料，对2014年8月西北太平洋和南海无TC生成的原因进行了诊断分析，结果表明：极地冷空气南侵，造成8月上中旬副热带高压偏东偏南，下旬冷空气减弱，副热带高压偏西偏南，致使副热带高压南侧偏东信风与赤道西风的汇合区位置异常偏南;马斯克林高压偏弱，导致索马里急流和东印度洋越赤道气流也弱，印度半岛中低层季风低压或季风槽极其不活跃。澳大利亚高压路径偏东或偏西和势力偏弱，则南海南部越赤道气流亦弱。8月上中旬台风主要源地的海表温度明显偏低，不能酿成低层高温高湿的大气；月内西北太平洋和南海大气的对流活动很弱，层结较稳定、风速垂直切变大，均不利于TC发生发展。在南海到菲律宾以东洋面低层为弱的正涡度区和负散度区，有辐合上升运动，但垂直速度很小，不能满足TC尺度的环流发生和发展；南亚高压和副高南侧东风扰动造成对流层高层为弱上升区，不能形成高空辐散机制，不利于上升气流维持和加强。故此，8月在异常偏南的ITCZ中生成的4个热带扰动最终均未能发展成台风。
中文关键词: TC，环流形势特征，季风低压，OLR，ITCZ
Abstract:Based on the conventional meteorological observation data, NCEP/NCAR 1°×1° monthly mean reanalysis data, the outgoing long wave radiation (OLR) data observed by the NOAA satellite and the data from the Typhoon Yearbook of China Meteorological Administration, this paper analyzed the causes for the no generation of tropical cyclones (TCs) in the northwestern Pacific and South China Sea (SCS) in August 2014. The results show that the invading of the polar cold air led to the further eastward and southward movement of the subtropical high in northwestern Pacific during the first twenty days in August. In the last ten days the cold air became weaker, then the subtropical high moved westward and southward, driving the convergence zone between the easterly trade wind in the south side of the subtropical high and the equatorial westerly to be located abnormally further southward than normal. The weaker Miscarene high caused the Somali jet and the cross equatorial flow over the eastern Indian Ocean to get weakened, and the low and mid level monsoon depression or monsoon trough over the Indian Peninsula to be extremely inactive. Additionally, along with the weaker Australian high and its position deviation, the cross equatorial flow over the southern SCS became weaker too. The SST of the tropical cyclone genesis was much lower than normal during the first dekad of August, so the warm and moist air in the area with lower SST could not form. In addition, the weak convection in the northwestern Pacific and SCS, the stable atmosphere and large vertical wind shear were unfavorable for the generation and development of tropical cyclone. In the lower level over the ocean between SCS and the east of Philippines, there was positive vorticity and negative divergence, but the convergence was not strong enough for the formation or development of TC. The weak updraft at the high level troposphere caused by the South Asia high and the easterly disturbance south to the subtropical high could not accomplish the upper level divergence process, being difficult to support the maintenance and intensification of the upward flow. Hence, the four tropical disturbances in the abnormally southward ITCZ did not develop into tropical cyclones.
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基金项目:国家自然科学基金面上项目（41575104）资助
| 作者 | 单位 |
| 李靓 | 南京信息工程大学公共管理学院，南京 210044 中国气象局公共气象服务中心，北京 100081 |
| 胡啸 | 中国气象局公共气象服务中心，北京 100081 |
| 王小光 | 中国气象局公共气象服务中心，北京 100081 |
| 康志明 | 国家气象中心，北京 100081 |
引用文本：
李靓,胡啸,王小光,康志明,2016.2014年8月西北太平洋和南海无TC生成之原因分析[J].气象,42(11):1325-1334.
LI Liang,HU Xiao,WANG Xiaoguang,KANG Zhiming,2016.Cause Analysis on the Lack of Tropical Cyclone’s Generation in the Northwest Pacific and South China Sea in August 2014[J].Meteor Mon,42(11):1325-1334.
李靓,胡啸,王小光,康志明,2016.2014年8月西北太平洋和南海无TC生成之原因分析[J].气象,42(11):1325-1334.
LI Liang,HU Xiao,WANG Xiaoguang,KANG Zhiming,2016.Cause Analysis on the Lack of Tropical Cyclone’s Generation in the Northwest Pacific and South China Sea in August 2014[J].Meteor Mon,42(11):1325-1334.