Most of the large scale multidisciplinary field experiments were conducted for limited time periods, spanning several weeks to months. These studies have been valuable in identifying parameters and processes affecting land-atmosphere interaction, but not as useful in hydrologic studies where longer time periods are required for quantifying water budgets over large areas. In addition, these shorter term studies do not provide information relevant to seasonal affects of terrestrial ecosystems and their impact on the hydrologic cycle. Shuttleworth (1988) described the value of long term measurements as a means of providing calibration for GCMs over representative biomes. This, of course, will only work when the biome is relatively uniform in vegetation cover and has a fairly weak precipitation gradient. An example of this type of field study is the Anglo-Brazilian Amazon Region Micrometeorological Experiment (ARME). These data were used in calibrating the Simple Biosphere Model (Sellers et al., 1989) and validating monthly evaporation and net radiation from climate models (e.g., Dickinson, 1989). Several other large scale field studies have permitted investigations of hydrological processes in different climates.