Effects of paddy fields on summertime air and surface temperatures in urban fringe areas of Tokyo, Japan

Abstract

A study was undertaken to determine the effect of paddy fields on air and surface temperatures in urban fringe areas in Tokyo, Japan. Air temperatures were measured at 1.5 m above the ground at 24 stations in Kasukabe City, Japan. These stations represented a range of paddy field distribution patterns from contiguous to highly segmented. Multispectral scans providing surface temperatures were recorded concurrently. Data were collected on successive hot days in August 1995. Measured surface temperatures varied by approximately 20 °C, while measured air temperatures differed by more than 2 °C. There was a strong correlation ( r = 0.8) between coverage ratio and temperature difference: the greater the area of paddy fields the lower the temperature. Further analysis identified a strong relationship between segmentation level and air temperature for areas of moderate coverage ratio. For the same coverage ratio, areas with a few large paddy fields had lower air temperatures than areas with many smaller paddy fields. This suggests that segmentation of paddy fields reduced their effectiveness in modifying the air temperature. Maximum temperature differerences were found in areas where the coverage ratio of paddy fields exceeded approximately 30% and the segmentation rate was low. This effect diminished as the segmentation rate increased. The results of this study will assist planners in determining appropriate configuration of land use in urban growth areas of Japan. These should also help planners understand the effects of land use decisions on the microclimates of urban areas.