西北太平洋变性热带气旋的若干特征  

Some characteristics on extratropical transition of tropical cyclones over the Western North Pacific

作　　者：宋金杰[1] 王元[1] 

机构地区：[1]南京大学大气科学学院中尺度灾害性天气教育部重点实验室,南京210093

出　　处：《南京大学学报（自然科学版）》2010年第3期328-336,共9页Journal of Nanjing University（Natural Science）

基　　金：国家自然科学基金(40830958;40730948;40775046;90715031);国家重点基础研究发展规划项目(2009CB421502);上海台风研究所基金(2008ST08)

摘　　要：本文利用JRA-25再分析资料,计算了1979-2007年西北太平洋热带气旋(TC)的3个气旋相空间参数.通过分析变性TC的相空间特征,发现变性TC具有热力结构的不对称性和高低层热力的冷异常,并将其作为识别TC变性的客观判据.对利用此判据修正后的1979-2007年《热带气旋年鉴》进行了统计分析,发现:变性TC的年频数和所有TC的年频数、变性TC的累年月频数与所有TC的累年月频数存在显著的正相关;变性TC所占的比例在春-夏和夏-秋季节转换时最高;强度越强的TC在其北上过程中越容易发生变性过程.When tropical cyclones（TCs） move over colder water and into stronger shear at higher latitudes,they often lose tropical characteristics and become more extratropical in nature,which is discribed as the extratropical transition（ET）.There have been many publications about the climatology and synoptic features related to TCs underwent ET.However,too little attention is paid to the quality of the data including TCs underwent ET.In this paper,the records of TCs underwent ET contained in the 1979-2007 tropical cyclone annual best-back data from the Shanghai Typhoon Institute is modified based on the cyclone phase space（CPS） method.There are three parameters（B,-VUL,and-VLT） coordinating the CPS,that are calculated from the JRA-25 global reanalysis data with the horizontal resolution of 1.25°×1.25°.TCs without ET hold the characteristics of symmetry and warm anomaly of thermal structure,while the thermal asymmetry and cold anomaly are the dominant features of TCs underwent ET.Since this,an objective discriminating method in the definition of ET is proposed,which reads ｜B｜10 m,-VUT0,and-VLT0.After the modification based on this criterion,some climatologic characteristics on TCs underwent ET in the period of 1979-2007 are obtained,which are concluded that： the annual（or monthly） number of TCs underwent ET is proportional to that of total TCs;the ratio of TCs underwent ET in total TCs is the highest in the transition periods of spring-summer and summer-autumn;TCs with higher intensities are more likely to complete ET in their northward moving.

关 键 词：热带气旋 变性 气旋相空间 

分 类 号：P443[天文地球—大气科学及气象学]