西北太平洋10~12月台风活动的年代际突变

Abstract

本文基于日本气象厅区域专业气象中心-东京台风中心(Regional Specialized Meteorological Center-Tokyo Typhoon Center, Japan Meteorological Agency)的热带气旋资料和欧洲中尺度天气预报中心(European Centre for Medium-Range Weather Forecasts)的再分析资料，在前人的研究基础上，对西北太平洋10~12月期间台风活动对大尺度环境因子年代际突变的响应进行了讨论，并且通过台风数量和相关大尺度环境因素的分析，对其影响机制进行了比较详细的阐述。分析西北太平洋1980~2013年10~12月生成的台风，与1980~1994年相比，10~12月的台风数量在1995~2013年期间显著减少。分析发现热带气旋最大潜在强度的年代际变化是导致1995~2013年西北太平洋热带气旋潜在生成指数(Genesis Potential Index, GPI)减少的最主要因素，1995年后西北太平洋SST异常场呈La Nina形态，导致热带气旋最大潜在强度(The Maximum Tropical Cyclone Potential Intensity, MPI)增大，但在热带气旋的发展过程中过早受到西边界的影响使得增强为台风的热带气旋减少。突变后垂直风切变增强造成西北太平洋东南部的动力条件不利于台风生成，这都是造成台风突变减少的原因。分析还发现垂直风切变主要对西北太平洋东南部的台风活动造成影响。 Based on the data sets of Regional Specialized Meteorological Center-Tokyo Typhoon Center, Japan Meteorological Agency and the reanalysis data of European Centre for Medium-Range Weather Forecasts, this paper demonstrated the decadal shift between October to December (OND) typhoon activity over the Western North Pacific (WNP) during 1980 to 2013, and discussed the response of the OND typhoon activity to decadal shift of the large-scale circulation. Meanwhile, by means of the analysis of typhoon activity and its relative large-scale environmental factors, it brought a detail exposition of its impact mechanisms. We analyzed that the WNP typhoon activity during October to December from 1980 to 2013, compared with that from 1980 to 1994, the typhoon activity during October to December among 1995 to 2013 decreased significantly. We discovered the main factor that led to the decrease of Tropical Cyclone Genesis Potential Index was the decadal shift of The Maximum Tropical Cyclone Potential Intensity. The anomalous SST patterns appear to be a La Nina pattern, leading to the increasing of MPI. However, it early affected by the western boundary during tropical cyclones development process so that fewer tropical cyclones enhanced to be typhoon. After 1995, the vertical wind shear and subtropical high to be strengthener, resulting in the southeastern Pacific Northwest dynamic conditions are not conducive to typhoon genesis; all these are the reasons for the decadal shift of typhoon activity. We also found the vertical wind shear mainly affects the eastern part of the Northwest Pacific typhoon activity.