+ Site Statistics
+ Search Articles
+ Subscribe to Site Feeds
EurekaMag Most Shared ContentMost Shared
EurekaMag PDF Full Text ContentPDF Full Text
+ PDF Full Text
Request PDF Full TextRequest PDF Full Text
+ Follow Us
Follow on FacebookFollow on Facebook
Follow on TwitterFollow on Twitter
Follow on Google+Follow on Google+
Follow on LinkedInFollow on LinkedIn

+ Translate

Potential evaporation functions compared on US watersheds: possible implications for global-scale water balance and terrestrial ecosystem modeling

Potential evaporation functions compared on US watersheds: possible implications for global-scale water balance and terrestrial ecosystem modeling

Journal of Hydrology Amsterdam 207(3/4): 147-169

Estimates of potential evaporation E(p) are commonly employed in terrestrial water balance and net primary productivity models. This study compared a set of 11 E(p) methods in a global-scale water balance model (WBM) applied to 3265 0.5 degree (lat. x long.) grid cells representing the conterminous US. The E(p) methods ranged from simple temperature-driven equations to physically-based combination approaches and include reference surface E(pr) and surface cover-dependent E(ps) algorithms. Cover-dependent parameters were assigned a priori based on grid cell vegetation. The WBM applies mean monthly climatic drivers and other biophysical inputs to compute water budgets on individual grid cells using a quasi-daily time step. For each E(p) method water budgets were computed and compared against mean monthly and annual streamflow from 679 gauged watersheds, assumed to be representative of the grid cells in which they reside. Procedures were developed for excluding watersheds for which this assumption was questionable, and 330 of the original 1009 watersheds were removed from further analysis. Among E(pr) methods, the range of mean bias relative to observed runoff, and thus simulated actual evapotranspiration E(s), varied from approximately -100 to +100 mm yr-1, E(ps) methods had a substantially smaller range, from about -50 to +50 mm yr-1. These results agree well with previous E(p) intercomparison studies at the point scale. Some individual methods from both the E(pr) and E(ps) groups yielded relatively small overall bias when compared with observed discharge data, suggesting the utility of simple as well as physically-based evaporation functions in continental- and global-scale applications. For any individual method, the spatial distribution of E(s) across the US was significantly altered relative to that of E(p) due to moisture-induced limits on soil drying. These limitations were most pronounced in hot, dry areas, where differences among E(p) methods in excess of 700 mm yr-1 were reduced to differences of less than 200 mm yr-1 in E(s) and runoff. There was a correspondingly higher sensitivity of E(s) to the choice of E(p) in more humid regions. These findings suggest that predictions made by macro-scale hydrology models like the WBM can be sensitive to the specific E(p) method applied and that this sensitivity results in bias relative to measured components of the terrestrial water cycle. The adoption of particular E(p) functions within such models should be conditioned upon the comparison of water budget calculations to suitable records of observed discharge.

Accession: 003237014

Download citation: RISBibTeXText

DOI: 10.1016/s0022-1694(98)00109-7

Download PDF Full Text: Potential evaporation functions compared on US watersheds: possible implications for global-scale water balance and terrestrial ecosystem modeling

Related references

Advances in the research on water and heat balance laws of the global terrestrial ecosystem. World Forestry Research 15(1): 19-28, 2002

Dynamic global vegetation modeling; quantifying terrestrial ecosystem responses to large-scale environmental change. Global Change - The IGBP Series 24: 175-192, 2007

Intercomparison of methods for calculating potential evaporation in regional and global water balance models. Water resources research 32(7): 2315-2321, 1996

Climate-driven uncertainties in modeling terrestrial energy and water fluxes: a site-level to global-scale analysis. Global Change Biology 20(6): 1885-1900, 2015

Terrestrial ecosystem interactions with global change. Papers submitted to the First Global Change and Terrestrial Ecosystem Science Conference, Woods Hole, Massachusetts, USA, 23-27 May 1994. Journal of Biogeography 22(2/3): 574 pp., 1995

Vegetation/ecosystem modeling and analysis project: Comparing biogeography and biogeochemistry models in a continental-scale study of terrestrial ecosystem responses to climate change and CO-2 doubling. Global Biogeochemical Cycles 9(4): 407-437, 1995

Potential productivity, yield gap, and water balance of soybean-chickpea sequential system at selected benchmark sites in India. Global Theme 3: Water, Soil, and Agrobiodiversity Management for Ecosystem Health. Report no. 1. Report Global Theme 3: Water, Soil, and Agrobiodiversity Management for Ecosystem Health (1): iv + 47 pp., 2002

Global review and synthesis of trends in observed terrestrial near-surface wind speeds; implications for evaporation. Journal of Hydrology 416-417, 2012

Testing the performance of a Dynamic Global Ecosystem Model: water balance, carbon balance, and vegetation structure. Global Biogeochemical Cycles 14(3): 795-825, 2000

Evaluation and analysis of a dynamic terrestrial ecosystem model under preindustrial conditions at the global scale. Global biogeochemical cycles 14(4): 1173-1190, 2000

Atmosphere-terrestrial ecosystem interactions: Implications for coupled modeling. Ecological Modelling 67(1): 5-18, 1993

Ecosystem CO2 starvation and terrestrial silicate weathering mechanisms and global-scale quantification during the late Miocene. Journal of Ecology 100(1): 31-41, 2012

Effects of global changes on above- and belowground biodiversity in terrestrial ecosystems: implications for ecosystem functioning. BioScience 50(12): 1089-1098, 2000

Modeling the total evaporation and water balance of a forest canopy. 17th Conference on Agricultural and Forest Meteorology and seventh Conference on Biometeorology and Aerobiology May 21-24-1985 Scottsdale Ariz: preprint volume sponsored by the American Meteorological Society: 264, 1985

A global terrestrial monitoring network integrating tower fluxes, flask sampling, ecosystem modeling and EOS satellite data. Remote Sensing of Environment 70(1): 108-127, 1999