THE RELATION BETWEEN SITUATION OF LAND COVER AND REGIONAL MICROCLIMATE IN WEATHER OBSERVATION POINT

－The extraction the degree of influence of land use change－

Abstract

 In recent years, global warming and the urban heat island phenomenon have become a serious problem not only in urban cities but also in local cities in Japan. One of the main causes is the change in land cover especially the loss of natural cover such as green spaces and water bodies and increase of artificial land cover such as buildings and asphalt coverage.
 In this study, we aimed to extract the degree of influence of the heat island phenomenon on the air temperature by analyzing the change in land cover and climate over the past 30 years across Japan. The study investigated the factors that influenced change in temperature at 288 weather observation points. Climate classification and geographical features analysis of all the stations was conducted. The results showed that the pacific side to the north from central Japan experienced a severe rise in temperature. Furthermore, the results showed that there was a moderate increase in temperature at points close to high altitude or latitude areas. In addition, we confirmed restraint in temperature at points close to the sea which were influenced by the effect of the water body.
 Investigation of the relationship between land cover and climate change showed that in the past 15 years there were many weather stations where there was decrease in natural land cover such as green spaces and an increase in artificial land cover. Moreover, in comparison to points with higher percentage of green cover, points with a higher percentage of artificial land cover showed a more rapid increase in air temperature.
  degree at which urban heat island phenomenon affects temperature was extracted from the yearly change in land cover of the selected regions. The results showed that in the period between 1985 to 2000, the average temperature gradient was 0.008°C per year. 14.3% of the temperature rise within the period was caused but the urban heat island phenomenon. In the period between 2000 to 2014, the average temperature gradient was 0.002°C per year. 22.2% of the temperature rise within the period was caused by the increase in urban heat phenomenon. Furthermore, as a secondary result, we found that after a certain percentage of green land cover is exceeded, the effect of restriction of temperature increase reaches its absolute peak.
 In order to understand the degree at which certain factors influence the air temperature increase, land cover condition, geographical features and wind patterns were stipulated as influencing factors. We quantified these factors and analyzed them using Hayashi's Quantification Method I. The analysis showed that latitude and land cover change had the greatest influence on the air temperature.
 From the above, this study extracted the degree at which the urban heat island phenomenon influences the temperature increase. In addition, we confirmed the influence of land cover change on the microclimate in an area. However, we could not analyze all the weather stations across Japan due to lack of satellite images in some points. Therefore, inclusion and analysis of these points and detailed investigation of the directional temperature around the weather stations are some of the points for further improvement in this study.