2:45 PM - 3:00 PM
[AAS06-05] mock mirage of suns including square suns and consideration of their factors
Keywords:mirage, square sun, Mock mirage, Reanalysis data, mirage of astronomical objects
A mirage of astronomical objects can produce distorted or multiple images of the target object. The most commonly observed are sunset and sunrise mirages (WMO, 2023). In particular, there are examples of phenomena in which the shape of the sun appears to be distorted in various ways, such as ”deformed sun”, ”deformation of the sun”, ”square sun”, and mock mirage of the sun.In Japan, the square sun at sunrise in Betsukai town, Hokkaido is advertised as a tourist resource and is famous nationwide. On the other hand, there is almost no meteorological research on detailed occurrence conditions and factors after collecting a large number of occurrence cases. Therefore, we collected 169 cases of outbreaks in Japan from public information such as the Internet, news reports, and research reports, as well as information provided by observers. Only those that can confirm the shooting place, date or year, and the photograph at the time of shooting are targeted, and deformation that seems to be within the range of change due to normal atmospheric differences is excluded. The target cases were from 2005 to 2023. Looking at the shooting period by month, there were cases in all months from January to December, and May was the most frequent. By season, there are 61 cases in spring , 46 cases in summer, 21 cases in autumn , and 41 cases in winter . In addition to the 9 prefectures of Nagasaki, Tottori, Ehime, Osaka, Chiba, Ibaraki, Yamagata, Toyama, and Hokkaido, there was also a case of the summit of Mt. Fuji. There were 113 cases in the morning and 56 cases in the evening, depending on whether they were taken in the morning (sunrise) or in the evening (sunset). In order to use it for the examination of the cause of occurrence, which will be described later, the photographs were classified into 4 patterns according to the magnitude of the change and characteristics. This classification is subjective, and the development of objective indices is a challenge. It should be noted that most of the cases are irregular observations, so it is necessary to be careful when grasping trends.
On the Betsukai Town website, the square sun is often explained as ”appearing during the midwinter (around February),” but it is not necessarily the midwinter.” (Betsukai Town, 2023). 96 cases were taken in Betsukai town, but there were cases of photographing in all months other than August, and it is possible to confirm that they have occurred outside of the severe winter season. In this way, even though it is limited to Betsukai town, it is not limited to severe winter, and although there are actually cases throughout the country throughout the year, why is it often explained that it appears during severe winter?
It is said that the square sun of Betsukai town came to be known around the 1970s, and in later years it began to be featured in magazines for photography enthusiasts. Among them, shooting conditions based on the experience of photographers, such as -20°C or below and -15°C or below, were introduced (DENiM, 1994; Shiki no Shashin, 1997). As the case of Betsukai town became known, the photographers gathered in the same place and continued to take pictures under similar conditions.
It is often explained that the cause of the formation of the square sun is related to the drop in temperature due to radiative cooling. However, it is quite possible that other mechanisms exist, and the theory that the inversion layer in the upper sky has an effect (Japan Mirage Association, 2016) ). Compared the temperature structure: Case 1) a square sun with a height; Case 2) a square sun with no height; and Case 3) at normal sunset with no anomalous deformation.For the analysis, the ECMWF reanalysis data ERA5 was used, and the vertical temperature profile at the time of photography was created from the photography point (43°54'55"N,144°41' 51"E) to about 400 km in the sunset direction (45°50'53"N,140°25'31"E). See attached diagram.
On the Betsukai Town website, the square sun is often explained as ”appearing during the midwinter (around February),” but it is not necessarily the midwinter.” (Betsukai Town, 2023). 96 cases were taken in Betsukai town, but there were cases of photographing in all months other than August, and it is possible to confirm that they have occurred outside of the severe winter season. In this way, even though it is limited to Betsukai town, it is not limited to severe winter, and although there are actually cases throughout the country throughout the year, why is it often explained that it appears during severe winter?
It is said that the square sun of Betsukai town came to be known around the 1970s, and in later years it began to be featured in magazines for photography enthusiasts. Among them, shooting conditions based on the experience of photographers, such as -20°C or below and -15°C or below, were introduced (DENiM, 1994; Shiki no Shashin, 1997). As the case of Betsukai town became known, the photographers gathered in the same place and continued to take pictures under similar conditions.
It is often explained that the cause of the formation of the square sun is related to the drop in temperature due to radiative cooling. However, it is quite possible that other mechanisms exist, and the theory that the inversion layer in the upper sky has an effect (Japan Mirage Association, 2016) ). Compared the temperature structure: Case 1) a square sun with a height; Case 2) a square sun with no height; and Case 3) at normal sunset with no anomalous deformation.For the analysis, the ECMWF reanalysis data ERA5 was used, and the vertical temperature profile at the time of photography was created from the photography point (43°54'55"N,144°41' 51"E) to about 400 km in the sunset direction (45°50'53"N,140°25'31"E). See attached diagram.