1980年代後半の全国的な冬季昇温に伴う降水量分布の変化と気圧配置型の影響

Abstract

Changes in precipitation distribution associated with a surface temperature rise in the late 1980s, which accompanied a climatic regime shift, are investigated using Automated Meteorological Data Acquisition System (AMeDAS) data of the Japan Meteorological Agency, and their relations with the variability of surface pressure patterns are revealed. After the temperature rise, the frequency of winter monsoon pressure patterns did not decrease. According to the classification of pressure patterns, long-term variations of surface pressure pattern frequencies showed negative relations between the winter monsoon and high-pressure patterns before 1992, which subsequently changed to the negative relations between the winter monsoon and traveling low-pressure systems. After the temperature rise, in years when low-pressure patterns prevailed, precipitation increases were observed in western Japan due to low-pressure systems traveling over the Pacific coast, and in wider areas from central Japan to Kyusyu areas due to low-pressure systems traveling over the Sea of Japan. Recently, the frequency of stationary front patterns has been increasing with precipitation increasing in the Setouchi area of western Japan. In years with a warm winter, precipitation increased in wider areas of the Pacific coast to inland areas of central Japan. In cold winters, low-pressure systems traveling over the Pacific coast decreased precipitation in central to western Japan. However, after a temperature rise, low-pressure systems traveling over the Sea of Japan decreased precipitation at the coast of the sea of Japan from central Japan to Hokkaido.