Hydrologic Evaluation on the AGCM20 Output Using Observed River Discharge Data

The controlled simulation output of a super-high resolution atmospheric model (AGCM20) was evaluated from a hydrologic point of view, using a distributed hydrologic model and observed river discharge data. The AGCM20 output for the current climate condition should be able to provide a current river flow pattern when it is converted into river discharge information using a reasonably well-prepared hydrologic model. For this evaluation, a distributed hydrologic model was composed for various basin scales ranging from 60 km(2) to 8,772 km(2) in the Tone River Basin, Japan, and calibrated in advance, using observed data of each sub-basin. Most sub-basins in the study area provide more than 25 years of observed discharge data, and the evaluations were conducted by comparing seasonal patterns of simulated and observed discharges. The result shows that the GCM output provides excellent discharge output when the basin scale is more than 5,000 km(2), while its utilization into a smaller basin remains limited. The proposed hydrologic evaluation method provides direct and comprehensive understanding to hydrologists in addition to the conventional evaluation method.