Temperature cross-section features in an urban area

This study examines the connection between the built-up urban surface and near-surface air temperature. The studied city (Szeged, Hungary) is located on a low and flat flood plain with a population of 160,000. Data were collected by mobile measurements under different weather conditions between March 1999 and February 2000. The efforts have been focussed on investigating the maximum development of the urban heat island (UHI) along an urban cross-section. According to the results, the UHI intensity changed according to season and month, as a consequence of the prevailing weather conditions. The role of cloudiness and wind speed on the temporal variation of the largest UHI, which represents the increasing effect of Szeged on temperature, is clearly recognized during most of the time in the studied period. The seasonal profiles follow remarkably well the general cross-section of the typical UHI described by Oke (Oke, T.R., 1987. Boundary Layer Climates. Routledge, London) who defines its characteristic parts as 'cliff', 'plateau' and 'peak'. The usefulness of the normalized values in the investigation is proved, the form of the seasonal mean UHI profile is independent of the seasonal climatological conditions, and is determined to a high degree by urban surface factors. As a conclusion, we suggest a modified model describing the metropolitan temperature variable for cities situated in simple geographical conditions: it is equal to the sum of components of the basic climate of the region and of the production of urbanization at the surface, where this last term is a multiplication of weather and urban surface factors. (C) 2001 Elsevier Science B.V. All rights reserved.