ENSO事件对西北太平洋热带气旋影响的分级研究

采用1951-2006年联合台风警报中心(JTWC)最佳路径数据集和气候预测中心(CPC) ENSO资料,分析了西北太平洋不同等级热带气旋累积能量(accumulated cyclone energy,ACE)与ENSO指数之间的关系.结果表明；ACE与ENSO指数间存在正相关关系；分级热带气旋中,ENSO事件主要通过超强台风(Super TY)的活动与ACE指数联系起来的,超强台风频数在El Ni(n)o期间多于La Ni(n)a 期间,同时持续时间也更长；ENSO指数和热带气旋活跃季超强台风ACE指数的滞后相关(ENSO指数滞后5个月内)与它们的同时相关大小相当.此外,还研究了分级热带气旋持续时间、强度和频数分别对ACE指数的贡献,结果显示超强台风频数的贡献最大.接下来,利用1951-2006年不同ENSO位相情况下NCEP再分析资料,分析了ENSO影响超强台风发生发展的物理机制.主要结论为:西北太平洋存在一些SuperTY频数与源地分布在ENSO年与平常年相比有明显差异的关键区；ENSO事件改变关键区低层相对涡度以及海表温度是其影响SuperTY源地及频数变化的重要途径.

Research on the effects of the ENSO on Tropical Cyclone Activity of different grades over the western North Pacific

Based on the 1951-2006 best tropical cyclone (TC) track dataset of the Joint Typhoon Warning Center (JJWC) and ENSO-related variables from the Climate Prediction Center (CPC). The relationship between northwestern Pacific accumulated cyclone energy (ACE) of different grades and ENSO are investigated. Results show that: ACE is positively correlated with ENSO indices. Among TC grades, Super-typhoon (SuperTY) contribute most to the relation between ENSO and ACE, the SuperTY amount is more and their lifetime are longer during El Niño episodes than those of La Niña ones. During the peak season of TC, the five-month lag correlation coefficient is almost as large as simultaneous correlation coefficient between the SuperTY ACE and ENSO indices. In addition, the contributions among annual mean TC lifetime, intensity, and amount of different TC grades related to the ENSO signal in ACE are compared, which suggest that the amount of SuperTY is the most important. Following, on the basis of the NCEP reanalysis data on different ENSO phases, the physical mechanism of the effect of ENSO on tropical cyclones of different degrees(especially the high intensity tropical cyclones), were also analyzed.It was concluded that there are some key zones in the Northwestern Pacific Ocean, where the number of the SuperTY in ENSO years is different from that in ordinary years. And ENSO events affect the genesis location and number of SuperTY mainly by changing the low-level relative vorticity and the sea surface temperature in some key zones.