気象観測点周辺における土地被覆状況と気候変化の関係について

－1985年から2016年の詳細解析－

抄録

 In recent years, temperature rise relevant to global warming and heat island phenomenon is regarded as a serious environmental problem. It is considered meaningful to study a cause of heat island phenomenon. Therefore, in the present paper two following analyses were conducted on 288 locations throughout Japan, among weather observation points by Meteorological Agency. The first analysis dealt with the relationship between the land covering situation and climate change from 1985 to 2016. The second analysis dealt temperature gradient by time. The purpose of these analyses is to clarify the relationship between land covering situation and climate change.
 Calculating the annual average temperature gradient from 1985 to 2016 at each meteorological observation point resulted in the increase in temperature at most weather observation points. Also, with respect to the highest temperature and the lowest temperature, both the highest temperature and the lowest temperature showed an upward trend, but especially the highest temperature rise was found to be intense. Analysis focusing on land covering shows that the lowest temperature is strongly influenced by land covering change. Also, when calculating the temperature gradient over time, it was found that the variation of the temperature gradient by the time zone was large in the city class. The rise in temperature during the day is small, which can be attributed to the expansion of solar shielding due to the middle to high-rise buildings. On the other hand, the temperature rise is remarkable from night to dawn. This tendency is considered to be due to the fact that the heat capacity of buildings etc. are large and the sky ratio is low because the sky ratio is low in the city class with many artificial coverings, the temperature does not decrease at night, and it coincides with the fact that the heat island phenomenon becomes manifest from night to dawn There. It became clear that this tendency is strengthened over time by increasing the ratio of artificial coating. In order to examine it in detail, the situation around the observation point was investigated using "Google Earth Pro" as a detailed analysis of hourly temperature gradient. The temporal change of the temperature gradient at most observation points among the 31 points of the city class showed the time change of the typical temperature gradient of the city. In addition, the daily range of temperature gradient varies from city to city, and land covering change is thought to have a big influence such as the influence of surrounding agricultural land.
 Humidity data accumulated and searched the relationship with land covering situation. Relative humidity tended to decrease nationwide. It was also confirmed that the relative humidity change varies depending on the difference in land covering, and the relative humidity shows a strongly decreasing trend in urban class etc. where the ratio of artificial coverings is large. On the other hand, it was found that the absolute humidity tends to increase with the passage of time. Although it has been reported that it was decreasing from 1951 to 1990, it may be thought that the trend of increase was from 1985 to around 1990. Moreover, the absolute humidity gradient was noticeable by season, and it turned out to be decreasing trend in winter. In other words, in the winter season, water vapor itself is decreasing and it seems that drying is progressing.
 As described above, detailed analysis was carried out to clarify the relationship between the land covering condition and climate change.