Linkage between urbanization and the change in extreme precipitation over the Tokyo metropolitan area, Japan

Abstract:

Extreme precipitation events cause flooding, threaten properties, and life, particularly in cities where is a high concentration of the human population. Understanding changes in precipitation extremes is critical to urban planners for building climate-resilient cities. Although there is evidence of cities modifying precipitation, uncertainties still exist around their role in precipitation extremes. As the home of more than 38 mil people, Tokyo is the most populous metropolitan area in the world. Urbanization here is known to impact the spatial and temporal patterns of precipitation significantly; however, its linkage with the extremes is not fully understood. This study uses historical-recorded hourly precipitation observation data to investigate the changes in extreme hourly precipitation over Tokyo metropolitan area for the last 40 years. We found the robust difference in the changes in number of hourly extremes between urban area and surrounding rural areas, though the difference in the intensities of the extreme events is not detected. This result, for the first time, suggested evidently the association between the urbanization and the change in extreme precipitation for Tokyo. Also, analysis of radar-based precipitation and satellite products was also conducted to robustify this result. With significant urbanization impact revealed, this study contributes to extensively ongoing discussion on urban precipitation extremes over cities in the world.