Abstract
Torrential rainfall is one of the important hydrologic event having a direct impact on urban hydrology. It is im-portant to have knowledge regarding the spatiotemporal patterns of torrential rainfall in order to prevent its ad-verse effects. Hence this study aims to present the spatiotemporal correlation characteristics of torrential rainfall events by the comparison of X-band MP radar data with 1-minute ground observation rainfall data in the upper basin of Kanda river in Tokyo. During typhoon, the meshed area of X-band MP radar data shows higher corre-lation with each ground observation rainfall data and this high correlation area having a spatiotemporal move-ment associated with the movement of the rainfall area. Even though the high correlation area having a spatio-temporal movement with the typhoon, the maximum correlation mesh is adjacently located with the overlap-ping mesh even in lag times of a few minutes. This can be attributed to the wide area coverage of typhoon and the small watershed under study. In cases of atmospheric instability, we can understand that the spatiotemporal correlation distribution is changing by every single rainfall peak by separating the duration of a multiple peak event by considering rainfall cell caused by torrential rainfall peak. The results shows the separation of multi peak rainfall event can cause the high correlation mesh area more widespread in case of particularly localized torrential rainfall. This can be interpreted as the effect of wind, upward air current, and the small area coverage of atmospheric instability.
