西北太平洋中尺度对流系统影响热带气旋生成的观测研究OA

This study develops a tracking algorithm for Mesoscale Convective Systems(MCSs)preceding tropical cyclone(TC)formation in the Western North Pacific from 2000 to 2023.MCSs resulting in TC genesis are designated as developing MCSs(D-MCSs),whereas systems that do not contribute to genesis are classified as non-developing MCSs(ND-MCSs).It is found that D-MCSs are present in environments characterized by elevated sea surface temperatures(SST)and a more humid mid-troposphere.They are also associated with enhanced low-level positive vorticity and increased high-cloud coverage.D-MCSs feature a deeper vertical vorticity structure with well-organized low-level convergence and upper-level divergence,indicative of enhanced convective organization.In contrast,ND-MCSs exhibit a shallower vertical structure and lack closed circulations.Further statistical analysis of D-MCSs reveals that those with more merging events exhibit prolonged durations from MCS formation to tropical cyclone genesis,larger initial vortex scales at cyclone genesis,and attenuated peak intensities over the TC's lifetime.The disparity in merging frequency is intimately linked to the spatial distribution patterns of MCSs.Cases featuring elevated merging events exhibit spatial concentration in the western sector of the Western North Pacific,where MCSs manifest greater spatiotemporal frequency.The propagation of MCSs is primarily modulated by large-scale circulation patterns.An intensified South China Sea monsoon trough induces a northwestward migration tendency in western systems,whereas enhanced low-level easterly steering flows associated with an intensified and expansive North Pacific subtropical high guide eastern systems westward.