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Research
Atmospheric and hydrospheric sciences
202101202101
Evaluation of the contribution of tropical cyclone seeds to changes in tropical cyclone frequency due to global warming in high-resolution multi-model ensemble simulations
Yamada Y, Kodama C, Satoh M, Sugi M, Roberts MJ, Mizuta R, Noda A, Nasuno T, Nakano M, Vidale PL
Global warming, Tropical cyclone, Tropical cyclone seed, Survival rate, High-Resolution, Model Intercomparison Project
Change ratio of TC genesis frequency, TC seed frequency, and survival rate. Horizontal axis indicates models. Change ratio was calculated based on the ratio of differences between mean values of the future climate (2025–2049) and the present-day climate (1990–2014) to the mean value of the present-day climate. In NCM014, we regard 2000–2009 as the present-day climate, and 2040–2049 as the future climate. Deep colored boxes indicate that its change is statistically significant at least 90% level with the Wilcoxon rank-sum test
Previous projections of the frequency of tropical cyclone genesis due to global warming, even in terms of sign of the change, depends on the chosen model simulation. Here, we systematically examine projected changes in tropical cyclones using six global atmospheric models with medium-to-high horizontal resolutions included in the sixth phase of the Coupled Model Intercomparison Project/High-Resolution Model Intercomparison Project. Changes in the frequency of tropical cyclone genesis could be broken down into the contributions from (i) the tropical cyclone seed, a depression having a closed contour of sea level pressure with a warm core and (ii) the survival rate, the ratio of the frequency of tropical cyclone genesis to that of tropical cyclone seeds. The multi-model ensemble mean indicates that tropical cyclone genesis frequencies are significantly decreased during the period 1990–2049, which is attributable to changes in tropical cyclone seeds. Analysis of the individual models shows that although most models project a more or less decreasing trend in tropical cyclone genesis frequencies and seeds, the survival rate also contributes to the result in some models. The present study indicates the usefulness of decomposition into the frequency of the tropical cyclone seeds and the survival rate to understand the cause of uncertainty in projected frequencies of tropical cyclone genesis.
