尺度相互作用对西北太平洋热带气旋生成频数的影响分析

Influence of Scale Interaction on Tropical Cyclone Genesis Number over the Western North Pacific

根据日本气象厅区域专业气象中心–东京台风中心(Regional Specialized Meteorological Center,RSMC)提供的热带气旋(Tropical cyclone, TC)最佳路径数据集,对盛期(7~10月)生成于西北太平洋的TC进行了统计,探究了其在年际上的差异及其产生原因。研究发现在TC生成频数异常偏高年,南海–菲律宾(10?N^20?N,110?E^130?E)和西北太平洋中东部(15?N^25?N,140?E^170?E) TC生成频数显著增多的主要原因是大尺度背景低频环流,季节内振荡(Intra-seasonal Oscillation, ISO)和天气尺度涡(Synoptic Scale Eddy, SSE)三者之间的正压能转换造成的。在南海–菲律宾地区,大尺度背景环境因子占主导作用,大尺度背景低频环流与SSE间的正压能转换导致SSE动能加强。该区对流层低层相对涡度和中层异常上升运动,为TC和SSE的生成发展提供了有利动力条件。而在西北太平洋中东部地区,季节内振荡(Intra-seasonal Oscillation, ISO)活动加强,伴随有利的动力条件,如低层较大的相对涡度和较小的垂直风切变,使得SSE从大尺度低频环流中获得正压能,导致该区SSE生成发展,TC生成频数增多。

Based on the best-track data of tropical cyclone(TC)provided by Regional Specialized Meteorologi-cal Center-Tokyo Typhoon Center of Japan Meteorological Agency(RSMC),a statistical analysis of TC genesis number was made and the reason for its difference on interannual scale was discussed.Results indicated that,during extreme high years of TC genesis number,the barotropic energy converted between large-scale low-frequency circulation,intra-seasonal oscillation(ISO)and syn-optic scale eddy(SSE)increased more TC over South China Sea-Philippines and eastern part of the Western North Pacific.As for the region of South China Sea-Philippines,large-scale background environmental factors played a dominant role.The barotropic energy conversion between large-scale background low-frequency circulation and SSE leads to the enhancement of SSE kinetic energy.The relative vorticity in the lower troposphere and the anomalous ascending motion in the middle troposphere provided favorable dynamic conditions for the generation and development of TC and SSE.As for the region of eastern part of the Western North Pacific,with the strengthened ISO activi-ty and favorable dynamic conditions,such as increased relative vorticity,anomalous ascending motion and decreased vertical wind shear,SSE obtained more barotropic energy from large-scale low-frequency circulation,which benefited the generation and development of SSE,and further led to more TC generate over this region.