Satellite measurements of albedo and radiant temperature from semi-desert grassland along the Arizona/Sonora border

Along the international border separating the U.S. (Arizona) and Mexico (So nora), differences in the grazing intensity of domestic livestock are commo nly presumed to have created a large difference in vegetation cover between the two countries. This vegetation difference is reportedly responsible fo r an extensive albedo and temperature discontinuity that may be affecting r egional climate. In this study, we used Landsat Thematic Mapper data to exa mine trans-border differences in these two biophysical parameters. Albedo a nd radiant temperature estimates were computed for 25 km-long (east-west) t ransects through semi-desert grassland on each side of the border at two di fferent times of year. Only small average trans-border differences in these parameters were found, and in some cases average albedo and temperature da ta were essentially equal on each side of the border. In addition, we found significant spatial heterogeneity in conditions on both sides of the borde r. These results suggest that, based on a small sample, it may be difficult to assess whether there are significant differences in biophysical propert ies of semi-arid grassland between Arizona and Mexico in the vicinity of th e border. We conclude that more extensive spatial and temporal sampling is critical in assessing any possible trans-border differences in average terr ain conditions that might affect climate, and that this data must be couple d with more extensive meteorological data to assess whether a difference in climate also exists.