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Title: Combined measurement and modeling of the hydrological impact of hydraulic redistribution using CLM4.5 at eight AmeriFlux sites

Effects of hydraulic redistribution (HR) on hydrological, biogeochemical, and ecological processes have been demonstrated in the field, but the current generation of standard earth system models does not include a representation of HR. Though recent studies have examined the effect of incorporating HR into land surface models, few (if any) have done cross-site comparisons for contrasting climate regimes and multiple vegetation types via the integration of measurement and modeling. Here, we incorporated the HR scheme of Ryel et al. (2002) into the NCAR Community Land Model Version 4.5 (CLM4.5), and examined the ability of the resulting hybrid model to capture the magnitude of HR flux and/or soil moisture dynamics from which HR can be directly inferred, to assess the impact of HR on land surface water and energy budgets, and to explore how the impact may depend on climate regimes and vegetation conditions. Eight AmeriFlux sites with contrasting climate regimes and multiple vegetation types were studied, including the Wind River Crane site in Washington State, the Santa Rita Mesquite savanna site in southern Arizona, and six sites along the Southern California Climate Gradient. HR flux, evapotranspiration (ET), and soil moisture were properly simulated in the present study, even in the facemore » of various uncertainties. Our cross-ecosystem comparison showed that the timing, magnitude, and direction (upward or downward) of HR vary across ecosystems, and incorporation of HR into CLM4.5 improved the model-measurement matches of evapotranspiration, Bowen ratio, and soil moisture particularly during dry seasons. Lastly, our results also reveal that HR has important hydrological impact in ecosystems that have a pronounced dry season but are not overall so dry that sparse vegetation and very low soil moisture limit HR.« less
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. Univ. of Connecticut, Storrs, CT (United States). Dept. of Civil and Environmental Engineering, Center for Environmental Science and Engineering
  2. Univ. of California, Irvine, CA (United States). Dept. of Earth System Science
  3. USDA-Agricultural Research Service, Tucson, AZ (United States). Southwest Watershed Research Center
  4. Univ. of Washington, Carson, WA (United States). Wind River Canopy Crane Research Facility, School of Environmental and Forest Sciences
  5. The Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA (United States)
Publication Date:
OSTI Identifier:
1283234
Grant/Contract Number:
SC0008182
Type:
Accepted Manuscript
Journal Name:
Hydrology and Earth System Sciences (Online)
Additional Journal Information:
Journal Name: Hydrology and Earth System Sciences (Online); Journal Volume: 20; Journal Issue: 5; Journal ID: ISSN 1607-7938
Publisher:
European Geosciences Union (EGU)
Research Org:
Univ. of Connecticut, Storrs, CT (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES northwest coniferous forests; soil-water; artemisia-tridentata; plant-roots; moisture; transpiration; vegetation; transport; patterns; climate