The GHAAS (USA) collection contains data used to compare water balance estimates over U.S. watersheds modeled by eleven potential evapotranspiration functions. The terrestrial water cycle is of critical importance to a wide array of Earth System processes. It plays a central role in climate and meteorology, plant community dynamics, carbon and nutrient ... biogeochemistry, and the structure and function of aquatic ecosystems. With a growing scientific consensus on the existence of CO2-induced greenhouse warming comes an increasing level of concern about how this climatic change will affect the terrestrial water cycle.
The primary objective of this study is to compare a set of potential evaporation functions that are commonly employed in global-scale water balance and terrestrial net primary production models as a precursor to estimating the realized or "actual" evapotranspiration. We assess these functions at the continental-scale using input data and validation targets distributed across the relatively data-rich conterminous United States. The model comparison results and analysis are described in Vorosmarty et al. Potential evaporation functions compared on US watersheds: Possible implications for global-scale water balance and terrestrial ecosystem modeling, Journal of Hydrology 207 1998 pp.147-169.
Water Balance Model (WBM)
The water balance model used in the GHAAS (USA) application simulates soil moisture variations, evapotranspiration, and runoff on single grid cells using biophysical data sets that include climatic drivers, vegetation, and soil properties. The state variables are determined by interactions among time-varying precipitation, potential evaporation, and soil water content. The original model is described in detail in Vorosmarty et al. (1989, 1996) and Vorosmarty and Moore (1991). For this application, the model was run to steady state using a set of climatologically-averaged datasets, described below.
Spatial resolution: 0.5 x 0.5 deg., latitude x longitude grids.
Temporal resolution: monthly, model estimates for a long-term-mean year. These data represent reference data.
This Collection contains 4 datasets which provide model predictions of actual evapotranspiration and runoff using two model run scenarios for rooting depth. A dataset for model prediction of potential evapotranspiration is also included as well as a dataset for model inputs. The model inputs dataset includes the following variables: % sunshine, solar radiation (cal-cm2/day), precipitation (mm/mon), vapor pressure (kPa), wind speed (m/s), temperature (min, max, mean, range) (deg. C), root depth, elevation, soil texture, land cover, runoff (mm/yr), dewpoint temperature (deg. C). Input data have been assembled from many sources, see Vorosmarty et al. (1998) or Data Center URL for more details.
The GHAAS (USA) collection contains data used to compare water balance estimates over U.S. watersheds modeled by eleven potential evapotranspiration functions as described in Vorosmarty et al. Potential evaporation functions compared on US watersheds: Possible implications for global-scale water balance and terrestrial ... ecosystem modeling, Journal of Hydrology 207 1998 pp.147-169.
Although the data may be used without restriction, there have been improvements to the climate input data sets in the years following the publication. The providers of these climate data sets encourage you to use their more recent data:
Climate Data from University of Delaware: Updates Climate Data from the Potsdam Institute for Climate Impact Research: Updates
Complex Systems Research Center
University of New Hampshire
Province or State:
Vorosmarty, C.J., C.A. Federer and A. L. Schloss. 1998. Potential evaporation functions compared on US watersheds: Possible implications for global-scale water balance and terrestrial ecosystem modeling, Journal of Hydrology 207: 147-169 pp.
Vorosmarty, C.J., Moore, B., Gildea, M.P., Peterson, B., Melillo, J., Kicklighter, D., Raich, J., Rastetter, E. and ... Steudler, P., 1989. A continental-scale model of water balance and fluvial transport: Application to South America. Global Biogeochemical Cycles, 3: 241-65.
Vorosmarty, C.J. and Moore, B., 1991. Modeling basin-scale hydrology in support of physical climate and global biogeochemical studies: An example using the Zambezi River. Studies in Geophysics, 12: 271-311.
Vorosmarty, C.J., Willmott, C.J., Choudhury, B.J., Schloss, A.L., Stearns, T.K., Robeson, S.M. and Dorman, T.J., 1996. Analyzing the discharge regime of a large tropical river through remote sensing, ground-based climatic data, and modeling. Water Resour. Res., 32: 3137-50.