A research group led by Associate Professor Kenichi Ueno of the University of Tsukuba has clarified the meteorological conditions of the sea of clouds that appear in the early morning at the western foot of the Yatsugatake mountain range.Furthermore, we have succeeded in identifying areas where seas of clouds are likely to appear in the central mountainous areas.
The sea of clouds is a landscape of clouds (lower clouds) that spreads like the sea below, not the weather on the spot.Although there is an explanation that applies the formation process of the lower clouds as the mechanism of the sea of clouds, there are few studies that observed the sea of clouds itself and analyzed the meteorological conditions and the area of occurrence.
In this study, on-site observations during the warm season were conducted for three years from 2017 to 2019 at the Fujimi Panorama Ski Resort in Fujimi Town, Suwa District, Nagano Prefecture.Furthermore, using the data of the meteorological satellite "Himawari 3", we clarified the days and areas where the sea of clouds is likely to occur in the central mountainous area.
As a result of the analysis, it was found that there are large-scale seas of clouds and small-scale seas of clouds that are biased to the east or west, and that the frequency of occurrence of large-scale seas of clouds is maximum from 5 to 6 in the early morning.On the other hand, it was suggested that the small sea of clouds biased to the east is a topographical gliding cloud * for the Yatsugatake mountain range.
In addition, we constructed an algorithm to empirically detect the spatial distribution of nighttime low-level clouds in the central mountainous area, and identified 12 regions where low-level clouds are likely to occur frequently during the warm weather.The existence of subsidence reversal (the lower the temperature, the lower the temperature) was confirmed in 6% of the days when lower clouds occurred at the same time in 67 of these areas (wide area occurrence days).In addition, a large sea of clouds was observed on the day of widespread occurrence with few upper clouds.
From the above, it was pointed out that it is important for the large-scale sea of clouds that appears in the mountainous areas of the Chubu Mountains in the early morning to have radiative cooling at night and the existence of sedimentary reversal due to the overall high pressure.The results of this research will lead to the creation of new research themes that link mountain weather with tourism resources.
The paper was published on August 2021, 8 in the 31th volume of the journal "Weather" of the Meteorological Society of Japan, entitled "Tendency of Sea of Clouds at Night in Central Mountainous Areas Based on Ground Observation and Satellite Data".
* Clouds are formed in the process of the moist air layer riding on the mountain.
