Recently, localized heavy rainfalls over heavily urbanized areas have caused severe damage in Japan. On 5 August 2008, a localized heavy rainfall caused a rapid increase in drainpipe discharge, which killed five people working in a drainpipe near Zoshigaya, Tokyo. This study investigated the effect of urban heating on this localized heavy rainfall by two ensemble experiments using a cloud-resolving model that included precise urban features. The first experiment (CTRL) considered realistic land cover, anthropogenic heat, and urban geometry. In the second experiment (WURB), to reduce only the urban heating and keep the urban geometry, the anthropogenic heat was ignored and the roofs, walls, and roads were covered by shallow water. The amount of rainfall was clearly reduced over Tokyo in the WURB experiment. The weaker surface heating in WURB reduced the near-surface air temperature and weakened the convergence of horizontal wind and updraft over the urban area, and resulted in the smaller amount of rainfall in WURB.
