Seasonal variations of the urban heat island in Kumagaya, Japan

Abstract

The seasonal variations of the urban heat island (UHI) phenomenon in Kumagaya, Japan were examined using multiple fixed-point observations of surface air temperature during a 1-year period. Horizontal distributions of surface air temperature observations in Kumagaya showed that UHI occurs continuously. The hourly average temperature difference between urban and rural areas was constant at ∼1°C. The UHI intensity (UHII) was calculated by dividing all observation points into urban and rural areas. Seasonal variation of daytime UHII was observed in Kumagaya, with maximum and minimum values in summer and winter, respectively. The observation of specific humidity during sunny days in summer suggested that the difference in the surface heat balance between urban and rural areas greatly contributed to the temperature difference between the two areas. Nighttime UHII in Kumagaya was the highest during April–May. These observations of maximum UHII may be explained by strong northwesterly flow over the mountains during winter and frequent calm and sunny days due to migratory anticyclone during April–May.