The 4th Japanese-German Meeting on Urban Climatology Tsukuba, 30th Nov. - 2nd Dec., 2005 A-4

Stationary Measurement and Analysis of Thermal Environment in Osaka Area, Japan

Atsumasa YOSHIDA, Masato MORIYAMA and Kazuma GONSUI Department of Mechanical Engineering, Osaka Prefecture University

Recently, the heat island phenomenon that the air temperature in urban area becomes higher than that in the suburbs and the surrounding rural area is confirmed in a lot of cities, for example Tokyo and Osaka in Japan. In summer, the thermal comfort in outdoor space is making worse and the photochemical reaction is activated according to the heat island phenomenon. The increase in energy for air-conditioning, and therefore the increase in the heat release according to it cause the vicious circle of rise of the air temperature further. The heat island task force is set up in Osaka Prefecture, and as the counter measures, the energy saving of the equipments and the promotion of greening on the rooftop and the trunk road are examined. In the present study, the stationary measurements have been performed in Osaka City, Sakai City and Hirakata City. The population is about 2.7, 0.8, 0.4 million, respectively. Sakai City is adjacent to the south of Osaka City. Osaka City and Sakai City face Osaka Bay. Hirakata City is located in 20 km in the northeastern direction of Osaka City along the Yodo River. A lot of cities continuously range to the Osaka Plains including these cities. The influence by the difference of the land use to the air temperature is clarified by measuring in the place where the land use is different. The influence by the strength of the land and sea breeze and the seasonal wind is also investigated. Moreover, the comparison of air temperature in three cities has been performed in consideration of the terrain position and the population. The air temperature distribution chart in Sakai City is made based on the stationary measurement data, and the current state of the thermal environment is clarified. The measurement device was set up in the instrument shelter in the elementary school. The number of measurement points was 8, 10, 17 in Osaka City including Higashi-Osaka City, Sakai City and Hirakata City, respectively. The measurement points in Osaka City and Higashi-Osaka City were arranged to queue up from the coastline to the inland in one straight line. The measurement points in Sakai City were chosen as the land use of surroundings was different. One measurement point of Hirakata City was put on all sides 2km. Continuous measurements were executed for about three months in Sakai City and Osaka City. The measurement periods were 2002/12/1-2003/1/30, 2003/7/1-2003/9/30, 2003/12/1- 2004/2/29, and 2004/7/1-2004/9/30. Similarly, continuous measurements were done for about two months in Hirakata City. The measurement periods were 2003/7/1- 2003/8/30 and 2004/7/1-2004/8/30. The measurement intervals were every ten minutes. The following conclusions were obtained as a result. (1) The air temperatures at a lot of measurement points in Osaka City were higher than those in the center area in Sakai City. The air temperatures in Hirakata City were almost the same as those in Sakai City. (2) When the sea breeze developed, the air temperature decreased in the Osaka Bay shore region. However, the air temperature rose in the east part of Osaka City region and Hirakata City where the sea breeze corresponded under the wind. (3) The air temperatures in Sakai City were the highest in the urban center area in the northwest part, and were lower in suburbs. A significant air temperature difference was admitted in both regions. It was confirmed that the heat island phenomenon appeared. (4) It was observed that there was a maximum air temperature difference of 6℃ at the clear and calm dawn in winter. (5) In daytime of summer, the air temperature decreased in the residential quarter around Osaka Bay coast area where the influence of the sea breeze was strongly received and the large-scale green parks.

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