How Does Tropical Cyclone Genesis Frequency Respond to a Changing Climate?

Global tropical cyclone (TC) genesis frequency (TCGF) has been documented to decrease or increase linearly in a changing climate. However, our numerical experiments show that the global TCGF exhibits a parabolic relation with spatio-uniform climate changes in sea surface temperature (SST) from -15 K to 5 K relative to the present climate, with the peak in the 5 K-cooler climate. The parabolic relation is found in all TC basins except the eastern North Pacific where TCGF keeps increasing with the changing climate. TCGF can be expressed as the product of the frequency of TC seeds and the TC survival rate (SR). Further analysis shows that this parabolic structure in the global TCGF depends on TC seeds rather than the TC SR. The TC SR exhibits an increasing trend with the SST increase, while TC seeds show a consistent change with TCGF, which might be linked to the changes in low-level relative humidity.

Automated summary

The global tropical cyclone (TC) genesis frequency (TCGF) shows a parabolic relation with spatio-uniform climate changes in sea surface temperature (SST) from -15 K to 5 K, with a peak in the 5 K-cooler climate. This parabolic relation is observed in all TC basins except the eastern North Pacific, where TCGF continues to increase with changing climate. TCGF can be measured as the product of TC seeds frequency and TC survival rate (SR). Analysis reveals that the parabolic structure in global TCGF depends on TC seeds rather than TC SR, with TC seeds showing consistent changes with TCGF possibly linked to low-level relative humidity.