Impact of Large-Scale Modulation of Seeds and Survival Rate on the Tropical Cyclone Genesis Frequency in the Northwestern Pacific
YUN Xing'e
YU Jinhua
ZHAO Haikun
Abstract：The large-scale environment serves as the background influencing the climatic characteristics of tropical cyclone(TC)genesis frequency.However,current TC genesis potential indices(GPIs),which are based on statistical relationships between environmental factors and TC formation,still require improvement in accurately characterizing the annual cycle of TC genesis frequency over the Northwestern Pacific.According to the theoretical framework of tropical cyclogenesis,TC genesis frequency can be expressed as the product of precursor disturbances(TC seeds)and their probability of developing into TCs.Based on this theoretical framework,the present study utilized TC best track data from the International Best Track Archive for Climate Stewardship and ERA-5 reanalysis data provided by the European Centre for Medium-Range Weather Forecasts to investigate the impact of large-scale environmental conditions on the climatic characteristics of tropical cyclone genesis frequency in the Northwestern Pacific.The results indicate that,based on the proposed theoretical framework,the product of the parameterized TC seeds and their survival rate can effectively characterize the annual cycle of TC genesis frequency in the Northwestern Pacific.In the entire Northwestern Pacific region,the correlation between the product of the two factors and TC genesis frequency was not significant.However,after dividing the entire region into eastern and western parts,we found that the product of TC seeds and survival rate showed significant correlations with TC genesis frequency in both regions.It was also observed that in the western region around the South China Sea and the Philippines Sea,the abnormal tropical cyclone genesis frequency was primarily controlled by both TC seeds and their survival rate.Vertical velocity and entropy deficit were identified as primary environmental factors affecting these two factors.Over the vast eastern Northwestern Pacific,on the other hand,the abnormal tropical cyclone genesis frequency was mainly influenced by variations in TC seeds,which were controlled by vertical velocity and relative vorticity.
Keywords：tropical cyclone genesis frequencyseed-probability frameworklarge-scale environmentparameterization
Publication Date：2025-02-28
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：10( 147-156 )