An assessment of satellite remotely-sensed land cover parameters in quantitatively describing the climatic effect of urbanization

The regional-scale climatic impact of urbanization is examined using two land cover parameters, fractional vegetation cover (Fr) and surface moisture availability (M-0) The parameters are hypothesized to decrease as surface radiant temperature (T-0) increases, forced by vegetation removal and the introduction of non-transpiring, reduced evaporating urban surfaces. Fr and M-0 were derived from vegetation index and To data computed from the Advanced Very High Resolution Radiometer (AVHRR), and then correlated to a percentage of urban land cover obtained from a supervised classification of Landsat TM imagery. Data from 1985 through 1994 for an area near State College, PA, USA, was utilized. Urban land cover change (at the rate of >3 per cent per km(2) per year) was statistically significant when related to a decrease in normalized values of Fr and increase in normalized values of T-0. The relationship between urbanization and M-0, however, was ill-defined due to variations in the composition of urban vegetation. From a nomogram of values of Fr and T-0, a Land Cover Index (LCI) is proposed, which incorporates the influence of local land cover surrounding urbanized pixels. Such an index could allow changes in land use at neighbourhood-scale to be input in the initialization of atmospheric and hydrological models, as well as provide a new approach for urban heat island analyses. Furthermore, the nomogram can be used to qualify urbanization effects on evapotranspiration rates.