Rainfall strength and area from landfalling tropical cyclones over the North Indian and western North Pacific oceans under increased CO2 conditions

Abstract

To understand the characteristics and changes in rainfall associated with landfalling tropical cyclones (TCs) from various perspectives, several studies have been conducted: 1) examining the characteristics and future projections of TC-induced rainfall in the North Indian Ocean (NIO) and western North Pacific (WNP), 2) investigating the influence of environmental factors on TC-induced rainfall and its future changes in the NIO, and 3) exploring the impact of environmental factors on TC-induced rainfall and its future changes in the WNP. Firstly, the rainfall characteristics of TCs were divided into rainfall strength (RS) and rainfall area (RA). Currently, the WNP exhibits higher intensity and larger area of TCinduced rainfall compared to the NIO. Moreover, the changes in rainfall characteristics under different scenarios of increasing carbon dioxide (CO2) varied across different regions. Particularly, in the NIO, there was a greater increase in RS, while in the WNP, the RA showed a larger increase. This indicates that TC-induced rainfall and the associated environmental conditions differ between regions. Secondly, the temporal and spatial relationships between TC-induced rainfall and environmental variables were examined in the NIO, focusing on the pre- and postmonsoon periods and dividing the region into the Arabian Sea and the Bay of Bengal. Regardless of the region, there was a close relationship between TC intensity and RS. It was observed that the frequency of TCs in the Arabian Sea. These findings suggest an increased risk due to the higher frequency and intense RS associated with TCs in the Arabian Sea, highlighting the need for appropriate measures. Lastly, in the WNP, the temporal analysis revealed that TC-induced rainfall predominantly occurs from July to October, while the spatial analysis divided the region into the South China Sea and East Asia. In terms of RA, all environmental variables showed significant relationships in the South China Sea, while in East Asia, mid-level relative humidity was not a significant factor and vertical shear played a particularly important role. This highlights the importance of understanding the regional variations and mechanisms that regulate TC-induced rainfall in the WNP. In conclusion, the studies provide insights into the characteristics and changes in precipitation associated with landfalling TCs in the NIO and WNP from different perspectives. The findings emphasize the need to improve our understanding of the regional factors that modulate TC-induced rainfall. Furthermore, considering the potential risks associated with increased TC frequency and intense rainfall, appropriate measures and policies should be developed for effective management and response within the affected regions.