Future Changes in Western North Pacific Tropical Cyclone Genesis Environment in High-Resolution Large-Ensemble Simulations

Hironori Fudeyasu,Kohei Yoshida,Ryuji Yoshida

doi:10.3390/oceans1040024

Abstract

This study applied the database for Policy Decision making for Future climate change (d4PDF) and tropical cyclone (TC) genesis (TCG) environment factors to project future changes in the frequency and characteristics of TCs over the western North Pacific. We examined current and future TCG environmental conditions in terms of the contribution of five factors: shear line (SL), confluence region (CR), monsoon gyre, easterly wave (EW), and Rossby wave energy dispersion from a preexisting TC (PTC). Among summer and autumn TCs, the contributions of SL and EW to future TCG increased by about 4% and 1%, respectively, whereas those of CR and PTC decreased by the same amounts. In future climate projections, the average lifetime maximum intensity (LMI) of TCs associated with EW (EW-TCs) was significantly higher than those of TCs associated with other factors except PTC. At higher sea surface temperatures and wetter conditions, higher lower-tropospheric relative vorticity was related to increases in the development rate of EW-TCs. Findings of this study suggest that increases in the average LMI of all future TCs were caused by large contributions from the average LMI of future EW-TCs.

Highlights

Many studies have reported predictions of tropical cyclone (TC) activity, including the frequency of TC genesis (TCG) and lifetime maximum intensity (LMI), under future global warming using high-resolution global models
preexisting TC (PTC)-TCs tended to occur in autumn, when many TCs formed at lower latitudes
This study investigated future changes in the frequency of TCG and TC characteristics in summer and autumn over the western North Pacific (WNP), stratified by TCG environmental factors classified by Ritchie and Holland [7], using the d4PDF large-scale ensemble dataset and the TCG score detection method (TGS) method

Summary

Introduction

Many studies have reported predictions of tropical cyclone (TC) activity, including the frequency of TC genesis (TCG) and lifetime maximum intensity (LMI), under future global warming using high-resolution global models. Yoshida et al [1], applied a large-scale ensemble dataset based on a high-resolution global atmospheric model the database for Policy Decision making for Future climate change (d4PDF) to assess the uncertainty of atmospheric internal variations and sea surface temperature (SST) increases; the frequency of global TCG was projected to decrease significantly and the proportion of intense TCs to increase by the end of the 21st century, based on the Representative Concentration Pathway 8.5 (RCP8.5) scenario. Over the western North Pacific (WNP), the TCG frequency was projected to decrease by about 40%, and the average LMI of TCs to increase by about 10%. Roberts et al [3] projected a Oceans 2020, 1, 355–368; doi:10.3390/oceans1040024 www.mdpi.com/journal/oceans

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Conclusion