2012年盛夏我国多台风特征及环流背景初步分析

Tentative analysis on multi-typhoon characteristics and atmospheric circulation background in the midsummer of 2012

利用西太平洋编号台风资料、NOAA卫星观测的地球向外长波辐射(OLR)资料、全球海表温度(SST)资料以及NCEP/NCAR逐日再分析资料,对2012年7—8月西太平洋地区生成并登陆或影响我国的台风特征及大尺度环流背景进行了初步分析。结果表明:7月中旬至8月底是当年台风生成和登陆的高度集中期,登陆比例之高、对我国影响范围之大等特征实属罕见;南亚高压偏强,中高纬"两脊一槽"环流型,东北地区为高压脊区,副热带高压稳定、强度增强且偏西偏北是这一时期的大气环流特征;副热带高压脊线位置在30°N以北有利台风初生,其南界位置偏北时,有利于部分台风生成于较高纬度,西伸指数持续偏高有利于台风集中登陆;夏季风明显增强和季风槽(ITCZ)位置变化、7—8月西太平洋SST正异常和OLR负异常可能是造成台风多发的原因,异常区域北界偏北也许是造成台风生成纬度偏北的原因。

Tentative analysis on multi-typhoon characteristics and atmospheric circulation background in China between July and August in 2012 is performed with the data of serially numbered typhoons in northwestern Pacific,outgoing long-wave radiation（OLR） data from NOAA,sea surfer temperature（SST） data and NCEP/NCAR reanalysis dataset.Conclusions are drawn that the typhoons originated and landed mainly in the period from mid-July to the end of August in China,and it is unusual that the percentage of typhoon landing is high and the area affected by typhoon is large.Atmospheric circulation characteristics in the period mainly show the stronger South Asian High,the two ridges and one trough pattern with a ridge in the Northeast China over the mid-and high-latitudes and the western Pacific subtropical high（WPSH） stabilized with increased intensity and more westward and more northward location.The ridge of WPSH locating in the north of 30°N is in favor of the genesis of typhoon and its south border moving northerly is in favor of formation of some typhoons in the higher latitudes,and more typhoons make landfall easily when the western extension index is continuously higher.The strengthen of East Asian summer monsoon,position changes of ITCZ,positive anomalies of SST over western Pacific and negative anomalies of OLR may be the reason to lead to the frequent occurrence of typhoon.And the extending northerly of north border of anomaly regions results in the origination of typhoons at the northerly latitudes probably.