A comparison study of atmospheric circulations and potential vorticity anomaly between the two rapid-intensified typhoons

对两次快速增强台风‘彩虹(2015)’和‘韦森特(2012)’的大气环流条件和高空位涡异常进行了比较。虽然两个台风的快速增强速率相似,但它们的大气环流条件差别很大。通过涡动量通量收敛方法,计算高空倒槽与台风环流的相互作用,发现高空倒槽为台风快速增强的发生提供了十分重要的线索。研究发现:一个孤立的正位涡柱在‘彩虹’台风开始快速增强前垂直发展,不受天气尺度位涡平流的影响。而对于‘韦森特’台风,来自高纬度位涡池沿高空倒槽方向,持续不断为台风环流输送位涡,有利于‘韦森特’台风快速增强。本文的工作为今后研究倒槽对台风快速增强的作用提供了理论依据。

For two rapid-intensification typhoons-Mujigae(2015)and Vicente(2012)-the atmospheric circulation conditions and potential vorticity(PV)anomaly are compared.Although similar in their rapid-intensification(RI)rate,their atmospheric circulation conditions differ considerably,with the absence or presence of an upper-tropospheric inverted trough(IT)being their main difference.The IT provides useful clues for the onset of RI,by estimating the interaction between the environmental upper-tropospheric IT and the typhoon based on eddy momentum flux convergence calculation.The trough–typhoon interaction is examined by comparing the PV transport process for the two cases.An isolated positive PV column develops vertically near Mujigae’s onset of RI,which is not influenced by synoptic-scale PV advection.However,for Vicente,another source-advection from a high-latitude PV reservoir along the upper-tropospheric IT-joins the built-up high-PV anomaly in favor of RI.