SEASONAL VARIATION AND SPATIAL DISTRIBUTION OF SURFACE REFLECTANCE AND ALBEDO: SATELLITE OBSERVATIONS OF AN URBAN/RURAL LANDSCAPE (LANDSAT, CONNECTICUT)

The spatial distribution and seasonal variation of surface reflectance and albedo in a heterogeneous urban/rural landscape (Hartford, Conn.) are examined using 27 calibrated Landsat observations.; The satellite data are calibrated, to remove atmospheric effects, by a target calibration procedure using 22 urban targets (building rooftops and parking lots) whose reflectance have been measured by a radiometer. Landsat bands 4 and 7, representing the visible and near infrared portions of the spectrum, are calibrated using linear regression analysis to relate the measured surface reflectance of the target to its satellite observed radiance. The resulting regression equations are used to predict surface reflectance from satellite observed radiance.; The visible and near infrared reflectance are combined into a measure of albedo by the use of weighted average schemes which incorporate the spectral reflectivity of the surface of interest and the spectral distribution of solar radiation. Three schemes are employed: for vegetated surfaces; for non-vegetated surfaces; and for snow-covered surfaces.; Results are presented according to 14 land cover categories adapted from the U.S. Geological Survey land/use land/cover classification system. Categories include urban, suburban, tree vegetation, and non-tree vegetation land covers.; The spatial distribution of albedo (for both snow-free and snow-cover observations) is examined using means, coefficients of variation, and statistical tests to ascertain significant albedo differences among categories. Urban/rural and snow-cover/snow-free differences of albedo are presented.; The seasonal analysis (for 23 snow-free observations) is conducted by fitting periodic curves to the data to derive a one-year cycle of reflectance. Mean monthly values of reflectance and albedo are calculated from the periodic curves.; The implications of albedo differences for selected categories are briefly discussed using blackbody surface radiant temperature calculations.; In addition to demonstrating the capability of satellite observations to measure surface reflectance in a complex landscape, this research establishes: the spectral nature of surface reflectance; the dependence of albedo on land cover; the seasonality of albedo (particularly for vegetation categories); and the lower albedo of urban areas.