复旦大学占瑞芬课题组近日取得一项新成果。他们报道了有利于北太平洋西部多热带气旋形成的环境条件。这一研究成果于近日发表在国际顶尖学术期刊《大气科学进展》上。

人们对多热带气旋(MTCs)的形成认识有限。本研究通过客观确定北太平洋西部上空有利于MTC形成的大气环流模式，探索有利于MTC形成的环境条件。研究人员根据1980至2020年6-10月发生的199次MTC事件，确定了四种不同的环流模式：季风槽(MT)模式占出现次数的40.3%，汇流带(CON)模式占26.2%，东风波(EW)模式占17.8%，季风环流(MG)模式占15.7%。

MT模式主要产生于副热带高压与季风槽的相互作用，MTCs沿季风槽及其侧翼形成。CON模式受副热带高压、南亚高压和季风槽的影响，MTCs出现在盛行西南气流和东南气流交汇的合流区。EW模式以偏东气流为主，MTCs沿偏东风波列发展。MG模式中的MTCs出现在以强烈的西南气流为特征的季风涡旋内。

定量分析进一步表明，在MT模式中，MTCs的形成主要受中层垂直速度和低层涡度的控制，而在其他模式中，中层湿度和垂直速度的影响显著。纬向风的经向切变和辐合是将正压能量从基本气流转化为扰动动能的重要过程，是涡旋动能增长的主要来源。

附：英文原文

Title: Environmental conditions conducive to the formation of Multiple Tropical Cyclones over the Western North Pacific

Author: Yining Gu, Ruifen Zhan, Xiaomeng Li

Issue&Volume:

Abstract: Limited understanding exists regarding the formation of multiple tropical cyclones (MTCs). This study explores the environmental conditions conductive to MTC formation by objectively determining the atmospheric circulation patterns favorable for MTC formation over the western North Pacific. Based on 199 MTC events occurring from June to October in 1980-2020, four distinct circulation patterns are identified: the monsoon trough (MT) pattern, accounting for 40.3% of occurrences, the confluence zone (CON) pattern at 26.2%, the easterly wave (EW) pattern at 17.8%, and the monsoon gyre (MG) pattern at 15.7%. The MT pattern mainly arises from the interaction between the subtropical high and the monsoon trough, with MTCs forming along the monsoon trough and its flanks. The CON pattern is affected by the subtropical high, the South Asian high and the monsoon trough, with MTCs emerging at the confluence zone where the prevailing southwesterly and southeasterly flows converge. The EW pattern is dominated by easterly flows, with MTCs developing along the easterly wave train. MTCs in the MG pattern arise within a monsoon vortex characterized by strong southwesterly flows. A quantitative analysis further indicates that MTC formation in the MT pattern is primarily governed by mid-level vertical velocity and low-level vorticity, while mid-level humidity and vertical velocity are significantly important in the other patterns. The meridional shear and convergence of zonal winds are important in converting barotropic energy from the basic flows to disturbance kinetic energy, acting as the primary source for eddy kinetic energy growth.

DOI: 10.1007/s00376-024-3237-4

Source: http://www.iapjournals.ac.cn/aas/en/article/doi/10.1007/s00376-024-3237-4viewType=HTML