The degree of urban heating in various parts of a city depends primarily on the local building density (1). It can be measured by a nadir-looking longwave radiometer mounted on a satellite or plane (2). So a relationship can be derived between the type of building (density) and the heating, allowing subsequent estimation of urban warmth from a map of land use alone. For the estimating of temperature at a point, it is necessary to allow for the type of surface and for the distance from adjacent surfaces. A weighting is allotted to various kinds of surface (3), e.g. 100 points for a dense residential area, 70 for a commercial/financial district, 60 for an area of separated homes, 50 for heavy industry, 30 for sports complexes, 20 for cemeteries and agricultural land. The impact of an adjacent district is assumed inversely proportional to its distance away.
(1) Oke, T.R. 1987. Boundary Layer Climates (Routledge) 435pp.
(2) Roth, M., T.R. Oke and W.J. Emery 1989. Satellite-derirved urban heat islands from three coastal cities. Internat. J. Remote Sensing,10, 1699-1720.
(3) Cornelis, B., M. Binard and I. Nadasdi 1997. Potentiels urbains et ilots de chaleur. Publs. Assoc. Internat. de Climatologie, 10, 223-9.