Inter-comparison of present and future urban climates of three cities considering multiple CMIP6 scenarios and urbanization
JIN XIAO, Do Ngoc Khanh, Alvin C.G. Varquez, Manabu Kanda, Ihara Tomohiko and Norihiro Itsubo

Dept. of Transdisciplinary Science and Engineering, Tokyo Institute of Technology (2-12-1 Ookayama, Meguro, Tokyo, 152-8550, Japan)

Abstract

Rising climate hazards in urban areas, driven by global warming and urbanization, are intensifying extreme weather events, threatening socioeconomic well-being. This study employs the pseudo-global warming method to project future climate and the Universal Thermal Climate Index (UTCI), which assesses human thermal comfort by considering temperature, humidity, wind, and radiation. We analyze all months of 2050 under three CMIP6 scenarios (SSP126, SSP245, SSP370), incorporating urbanization effects (i.e. spatial changes in distribution of buildings and anthropogenic heating) for Tokyo, Cairo, and Jakarta. With a humid subtropical climate, Tokyo faces population decline reducing AHE in the future. Cairo^s arid desert climate contends with overpopulation. With a tropical monsoon climate, Jakarta is assumed to experience rapid urbanization. We find global warming affect the extreme values of near-surface temperatures in three cities and the effects are more pronounced in Jakarta and Cairo compared to Tokyo. Urbanization in Jakarta cause UTCI increases in the northwestern and central areas across all scenarios, varying by month. Near-surface temperatures decrease in the northeastern areas but increases in central Jakarta. In Cairo, urbanization generally leads to increases in both UTCI and near-surface temperature throughout the year for all scenarios, except for October under SSP245. Despite warming induced by background climate change, Tokyo will exhibit lower temperature increases in near-surface temperature under future urban conditions, primarily due to a declining population and reduced anthropogenic heat emissions. However, occasional UTCI increases were found on certain months and scenarios.
This work was supported by JSPS KAKENHI Grant Numbers JP21H04573, JP21K14249, JP23H03599.

Keywords: CMIP6 scanarios, urbanization, weather forecasting, universal thermal comfort index

Topic: Interdisciplinary Earth Science and Technology