Junichi Yoshitani

Atmospheric Model-Based Streamflow Forecasting at Small, Mountainous Watersheds by a Distributed Hydrologic Model: Application to a Watershed in Japan

In this study, an experimental 12-h lead-time flood forecasting methodology that combines the fifth generation mesoscale model (MM5) of the U.S. National Center of Atmospheric Research with the physically based, spatially distributed watershed environmental hydrology (WEHY) model is described and applied to the Shiobara Dam watershed in Japan in order to explore its utility. The Shiobara-Dam watershed is a mountainous steep-sloped watershed that has an area of 123  km2 . Meanwhile, the routine atmospheric assimilation data that are provided by the Japan Meteorological Agency (JMA) over Japan, have spatial resolution of 20 km and are at 12-h time intervals. In order to utilize the JMA’s atmospheric data at 12-h intervals as initial and boundary conditions for 12-h lead-time hourly precipitation forecast inputs to the WEHY model of Shiobara-Dam watershed for runoff forecasts, the MM5 nonhydrostatic atmospheric forecast model was chosen and nested inside the JMA’s data domain. The JMA’s atmospheric data were...

Application of a Coupled Regional-Scale Hydrological-Atmospheric Model to Japan for Climate Change Study

This paper presents the improved performance of a regional climate model for the Japan region when a fully coupled boundary layer model and an areally averaged land–surface flow model are employed. It also describes results from the application of the regional climate model to the region for climate-change prediction. An integrated regional-scale hydrological-atmospheric model (IRSHAM) was developed for the Japan region that consisted of a 60-km resolution large-domain model nesting a 20-km resolution small-domain model. The small-domain model was equipped with two-way interaction between the areally averaged land–surface parameterization and the first layer of the atmospheric model. A historical period was then simulated by IRSHAM for local precipitation and other hydrological processes. Simulation results showed a significant improvement in the monsoon-affected regional distribution of monthly precipitation in the Japan region. The simulation results correlated with their counterparts observed at the Ts...