Host: The Association of Japanese Geographers
Name : Annual Meeting of the Association of Japanese Geographers, Spring 2020
Date : March 27, 2020 - March 29, 2020
Firstly, it is thought that the daily diurnal temperature changes when the weather is calm, and reaches the maximum daily temperature 3 hours after the south of the sun. However, in practice, advection caused by various phenomena such as general control stations and local circulation influences, and sometimes changes the daily temperature change in the affected area. For example, according to Watarai et al. (2009), the time when the highest temperature on August 16, 2007 was 40.9℃ in Kumagaya, Saitama was 14:42 JST. On the other hand, in Maebashi City, Gunma Prefecture, which is about 40 km northwest of Kumagaya City, the time when the maximum temperature was 38.1℃ was observed at 13:21 JST. Was 81 minutes earlier. In addition, the time of the sun's southern day was around 11:48 in Maebashi, Gunma, and around 11:45 in Kumagaya, Saitama. It has been pointed out that the effect of gap flow due to Fern is one of the factors. In the Pacific coast, there were some places where daily maximum temperature appeared earlier than Maebashi and Kumagaya due to sea breeze. However, this is the case from August 15 to August 16, 2007, and it is thought that daily atmospheric conditions and regional characteristics are modulating daily temperature variations in various places. Few studies have investigated the climatological characteristics of daily temperature changes on sunny days, focusing on the time of day when the highest temperature appears. The purpose of this study was to investigate the characteristics of the daytime maximum temperature appearance on a clear day in the plains of the Kanto region, and report the results.
The analysis period is 11 years (January 1, 2009-December 31, 2018), and uses data from the Meteorological Agency's Meteorological Office, Special Area Meteorological Observatory and AMeDAS Observatory. The data used were the daily maximum temperature appearance time and sunshine duration of daily values, and the wind direction and wind speed of hourly values. The analysis target area is 82 sites in the Kanto region and 54 sites in Niigata and Nagano prefectures in the Shinetsu region on the windward side (excluding islands in both the Kanto and Shinetsu regions). The analysis method used daily sunshine hours on sunny days, defined as 7 hours or more from November to January, 10 hours or more from May to July, and 8.5 hours or more in other cases. If it is a sunny day and there is no influence from advection, etc., the temperature will change daily so that the maximum daily temperature will be about 3 hours after the south mid-sun time (Japan standard time: 15:00) and the minimum daily temperature will be about the time of sunrise. As an index, we investigate the characteristics of seasonal sunny days and the differences in characteristics due to surface wind direction and wind speed. Based on hourly surface wind data in the Kanto and Shin-Etsu regions, we plan to conduct surveys based on daytime average wind speed and prevailing wind direction.
This time, 14 of the 82 locations in the Kanto region (Kitaibaraki, Mito, Tsukuba (Tateno), Utsunomiya, Sano, Maebashi, Kumagaya, Saitama, Choshi, Chiba, Tateyama, Tokyo, Yokohama, Odawara) on a sunny day This is shown in the appearance time characteristics. As a result, 447 cases out of all 3652 cases were observed on all 14 sites on clear days. In each season, 159 cases occurred in spring, 41 cases in summer, 73 cases in autumn, and 174 cases in winter. We also investigated the average time of daily maximum temperature at 14 locations. As a result, the maximum daily temperature was found between 13:50 and 14:30 on average in the inland Kanto area, and on average between 13:00 and 14:00 in the Kanto coastal area.
View PDF for the rest of the abstract.
