Changes in Extremes Indices over Japan Due to Global Warming Projected by a Global 20-km-mesh Atmospheric Model

Abstract

Changes in indices of extremes between the present-day climate and a future warmer climate are projected over Japan using a global 20-km-mesh atmospheric model. Comparisons with observed data show that the indices on temperature extremes are represented well in the model, while less intense precipitation biases are found. In the future climate simulation around 2090, the number of frost days decreases by 20-45 days with larger decrease along the Sea of Japan than the other area. Growing season length increases about a month. Changes in the temperature extremes are not uniform over Japan, showing usefulness of projections using a high-resolution model. Although changes in precipitation extremes are small and not significant over a large part of Japan, statistically significant increase in indices of heavy precipitation is found in western part of Japan and Hokkaido.