This study was conducted to estimate vapor supply from irrigated cropland using the hydrological land surface model and the atmospheric water balance method. Based on observation-based meteorological forcing, the authors have estimated vapor supply using the hydrological model: SiBUC. Vapor supply has been also estimated by the atmospheric water balance method using reanalyzed climate data: JRA-25. Vapor supply estimated by SiBUC with irrigation well suits to estimated vapor supply from atmospheric water balance on irrigated land in north China and United States. It suggests that land surface models including irrigation reproduce vapor supply well compared with models including no irrigation.

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In recent years, the damage caused by extreme weather events has frequently been reported in many parts of the world. Therefore the improvement of prediction accuracy for extreme events is an urgent issue. This study conducted to evaluate the sub-seasonal forecast skill with land initializations in an Atmospheric General Circulation Model (AGCM) targeting a severe drought event which occurred in the North American continental in boreal summer of 1988. The experiment using land initialization with influence of human activities, sub-seasonal forecast skill for near surface temperature improved its skill comparing with another forecast experiment without realistic land initializations. We obtained the result of forecast that soil moisture states could come to have a long dry state by considering human activities at the drought event.

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We have compared differences in hydrological simulation results when two different types of bias correction methodologies were applied to general circulation model output. The methodologies are: (1) a shifting-and-scaling method and (2) a quantile mapping method. Similar seasonal variations of 30-year-mean river discharge were obtained for the both bias correction methods. However, for the maximum monthly discharge in 30 years, the shifting-and-scaling method tends to produce larger values than the quantile mapping method. This feature attributes characteristics on multiplication factors for producing future precipitation data: The maximum end of a precipitation range is selectively affected by the factor. This feature might overestimate future risks of flooding. Since future projection of the river discharge directly links to evaluation of risks accompanied with future climate changes, we should pay attention to bias correction methods when we interpret hydrological simulation results.

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An integrated multi-scale simulation method of flow and sediment transport in rivers is required for river channel designs and maintenance managements. This paper highlights the need of a new depth integrated model without the assumption of the shallow water flow for integrated simulations of 2D and 3D phenomena in rivers, indicating the applicable ranges and limitations of previous depth integrated models. The general Bottom Velocity Computation method without the shallow water assumption is proposed and its applicability for flows with 3D structures and bed variations is discussed in this paper. The unified calculation method for integrated multi-scale simulations is presented to elucidate flow and sediment transport in laboratory channel and rivers during flood. Finally, we discuss issues to be solved and the future works toward integrated multi-scale simulations of flow and sediment transport in rivers.

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