5:15 PM - 6:45 PM
[MIS11-P05] Meteorological observation in Mumaya basin
Keywords:Mountainous region, Cold air pool, low temperature
The Rokumaya area in Shokawa-mura, Gifu Prefecture, is one of the observation sites of AMeDAS, and is the area where many of the lowest temperatures in Honshu have been observed. This low temperature is thought to be due to a cold-air lake phenomenon resulting from the basin topography of Rokumaya. The cold-air lake is a phenomenon in which air cooled by the surrounding slopes stays at the bottom of the basin due to mechanical effects. The valley topography is different from that of a pure basin topography. In this study, meteorological observations were conducted in the Rokumaya Basin to elucidate the formation mechanism of cold air lakes in the Rokumaya area, which is rich in topographical features.
Meteorological observations were made at an elevation of 1006 m above sea level (36.06°N, 137.03°E) at the bottom of the Rokumaya basin in Shokawa-cho, Gifu Prefecture. Observations included air temperature, humidity, atmospheric pressure, wind direction, wind speed, snow depth, upward and downward shortwave radiation, and longwave radiation. Snow depth was recorded every hour, and other data were recorded at 10-minute intervals. The data were analyzed from November 27, 2022 to November 15, 2023. In addition to the meteorological observation data, hourly precipitation data were obtained from the JMA's AMeDAS station (Rokumaya; 36.05°N, 137.03°E) and used in the analysis.
The lowest temperature of -17.2°C was recorded at 7:20 a.m. on January 11, 2023 in the 10-minute observation period. This cold event also occurred in the morning of the following day, January 12, when the minimum temperature was -16.1°C. Wind speeds remained windless from 23:20 on January 9, 2023 to 10:20 on January 11, 2023. These facts suggest that radiative cooling prevailed at that time, resulting in lower temperatures at the bottom of the basin.
Meteorological observations were made at an elevation of 1006 m above sea level (36.06°N, 137.03°E) at the bottom of the Rokumaya basin in Shokawa-cho, Gifu Prefecture. Observations included air temperature, humidity, atmospheric pressure, wind direction, wind speed, snow depth, upward and downward shortwave radiation, and longwave radiation. Snow depth was recorded every hour, and other data were recorded at 10-minute intervals. The data were analyzed from November 27, 2022 to November 15, 2023. In addition to the meteorological observation data, hourly precipitation data were obtained from the JMA's AMeDAS station (Rokumaya; 36.05°N, 137.03°E) and used in the analysis.
The lowest temperature of -17.2°C was recorded at 7:20 a.m. on January 11, 2023 in the 10-minute observation period. This cold event also occurred in the morning of the following day, January 12, when the minimum temperature was -16.1°C. Wind speeds remained windless from 23:20 on January 9, 2023 to 10:20 on January 11, 2023. These facts suggest that radiative cooling prevailed at that time, resulting in lower temperatures at the bottom of the basin.