Net radiation calculated from remote multispectral and ground station meteorological data

Of the four terms that comprise net radiation, the incoming solar and the longwave radiation from the atmosphere are essentially independent of surface conditions (e.g., bare soil, vegetation). These terms can be measured at a single location using groundbased instruments and extrapolated over relatively large areas. The reflected solar and the emitted longwave terms are surface dependent, but are amenable to measurement by remote means. A method is described whereby net radiation is evaluated by combining ground-based meteorological and remote multispectral measurements. Net radiation values obtained using the remote method were compared to values obtained using minature net radiometers. The net radiometers were positioned near the center of 18 wheat plots and the multispectral measurements were made over a 6-m transect on each plot. Although the two methods used instruments having different fields-of-view, good agreement was obtained. The results imply that, by combining ground-based and remote measurements, net radiation maps of relatively large areas can be constructed at the level of detail determined by the resolution element of the multispectral radiometer.