[A-HW21] Interdisciplinary approach to support climate change adaptation measures in regional scale

[AHW21-P01] Attempt to separate factors to reduce locality of precipitation-elevation dependence in Japan

*Mayu Otsuki¹, Atsushi Higuchi², Hitoshi Hirose³ (1.Chiba University, 2.Center for Environmental Remote Sensing Chiba University, 3.Japan Aerospace Exploration Agency)

Keywords:Elevation dependence, Orographic precipitation, Radar AMeDAS, Precipitation, Topography

Japan is located in the northwest of the Pacific Ocean. There is the Sea of Japan between Japan and the Eurasian continent. Japan, which has such geographical characteristics, has a climate different from other regions in the mid-latitude. For example, the annual precipitation amount in the mid-latitude is approximately 800 mm, while 1700 mm in Japan. The orographic effect attributes such regional differences in annual precipitation in precipitation. Forced rise aloft the airmass by the mountain enhances the condensation; thus, the mass of precipitation varies with the elevation. It is well-known as elevation dependence. Previous studies have been conducted on the elevation dependence over various regions, but not many analyze Japan. Therefore, this study analyzed the elevation dependence of precipitation in Japan from 2016 to 2018 using radar AMeDAS analysis rainfall. Hokkaido and Nansei Islands are excluded due to different climatic zone with Japan's mainland. In addition, the areas over 1000 m in elevation are masked to take into account radar-beam shielding. Since the elevation dependence dramatically depends on the precipitation and topographical characteristics of the region, this study aimed to separate the factors that bring regionality to the elevation dependence and evaluate Japan's elevation dependence more universally. At this time, we hypothesized that the factors that cause regional differences in precipitation are "frontal precipitation," "typhoons," and "cold outbreak precipitation in winter." Not only do these precipitation systems bring large amounts of precipitation to some areas, but they also have different elevation dependence. Therefore we separated these factors. After removing these three factors, the regional difference in annual precipitation amount becomes more homogeneous. Its amount is approximately 800 mm, which close to the mid-latitude's value. Seasonal variability in separated precipitation was analyzed. There was a clear regionality in the season when precipitation was brought about.