Relationship between Cold-Air Damming and Heavy Precipitation in the Kanto Region

In this study, we detected and analyzed cold air damming (CAD) and precipitation occurrences spanning 40 years from 1980 to 2019 in the Kanto region. We explored the climatological relationship between CAD and heavy precipitation. Of the 13.5 CAD events per year, 4.0 were associated with 24-h precipitation of 100 mm or more. In the southern Kanto region except for the western mountainous area, more than 25% of heavy precipitation was related to CAD, reaching over 40% in parts of the Boso Peninsula. CAD events with heavy precipitation exhibited consistent characteristics throughout seasons, including (1) a pronounced pressure gradient between the well-developed low-pressure off the southern coast of western Japan and the high-pressure on the northeast side of Japan, and (2) a strong moisture influx toward the Kanto region. These features highlight the crucial and general mechanisms of heavy precipitation formation through significant moisture ascent over the cold air dammed over the Kanto region.