In order to clarify the spatial and temporal variation of surface air temperature patterns in Osaka City, we applied principal component analysis and cluster analysis to characterize its diurnal variation patterns using 10-minute interval surface air temperature data obtained at 60 stations both in summer (July to August 2011) and in winter (December 2012 to February 2013). The first principal component in summer (winter), which the authors interpreted as characteristic of night time air temperature, explained 51.9% (60.4%) of the total variance. The second one, which was interpreted as characteristic of daytime air temperature, explained 27.1% (26.2%) of that. We found central area in Osaka City experience higher temperatures at night than surrounding areas due to the urban heat island effect. For the cluster analysis, 60 stations were grouped into 4 (3) types of diurnal variation of surface air temperature patterns in summer (winter), which were described by daily minimum temperature which acts as a primary factor and, only in summer, daily maximum temperature which acts as a secondary factor.

The purpose of this study is to investigate the actual situation of land surface temperature and is to analyze the hot environment. This research clarified the distribution of land surface temperature in Suita City by using a thermal infrared sensor mounted on an aircraft. By using the thermal image data, the effects of land use on the temperature was revealed quantitatively. We developed the model to explain the Grove temperature and WBGT (Wet-Bulb Glove Temperature) which is the index of hot environment. This model figured out the effects of solar radiation and land surface temperature on WBGT.

We have estimated the distribution of the surface temperature in Sakai city, at 1400 LST and around 2300 LST in midsummer, from the infrared thermal image data obtained from aerial observations and the ground level measurements. The relation between land use and the surface temperature were investigated.
In the daytime the surface temperature of the area where latent heat transport is dominant (sea, river, forest, park, etc.) is relatively low, however, the surfaces of their surroundings are not cooled because the surface temperature largely depends on the thermal characteristics of the surface material. In the nighttime, the surface temperature of inland water, such as reservoir ponds and moats of ancient tombs, shows the highest value among the land use categories. In the daytime the surface temperature of the middle- and high-rise residential areas is almost same as the low-rise spaced residential area. On the other hand, the surface temperature of the middle- and high-rise residential areas shows relatively higher value than the low-rise spaced residential area in the night time because the heat capacity of the buildings is large and the covering ratio of paved surface is high.