Vertical Temperature Profiles with Light Breezes at Night in Urban and Rural Areas of Obuse, Nagano

This paper describes the vertical structure of the nocturnal heat island in a small town. Tethered balloon soundings were conducted 180 times in and around an urban area on nights with light winds from March 2003 to May 2005. Surface inversions developed not only in rural areas but also in urban areas. Surface inversions developed quickly after sunset at the rural site, whereas development was slower at the urban site. At six hours after sunset the verticaltemperature profile in the urban area was the same as that in the rural area. Heat island formation in the small town was related to the delay in the development of surface inversion in the urban area. The crossover effect can be seen in only three of 23 surveys for which vertical soundings were performed in both urban and rural areas