Observed and simulated water and energy budget components at SCAN sites in the lower Mississippi Basin |
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| Authors: | Gabriëlle J M De Lannoy Julie Ufford Alok K Sahoo Paul Dirmeyer Paul R Houser |
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| Institution: | 1. George Mason University and Center for Research on Environment and Water, 4041 Powder Mill Road, Suite 302, Calverton, MD 20705‐3106, USA;2. Laboratory of Hydrology and Water Management, Ghent University, Coupure links 653, B‐9000 Ghent, Belgium;3. Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ 08544, USA;4. Center for Ocean‐Land‐Atmosphere Studies, 4041 Powder Mill Road, Suite 302, Calverton, MD 20705‐3106, USA |
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| Abstract: | Land surface models are typically constrained by one or a few observed variables, while assuming that the internal water and energy partitioning is sensitive to those observed variables and realistic enough to simulate unobserved variables. To verify these assumptions, in situ soil climate analysis network (SCAN) observations in the Lower Mississippi Basin (2002–2008) are analysed to quantify water and energy budget components and they are compared to Community Land Model (CLM3·5) simulations. The local soil texture is identified as a major indicator for water storage characteristics and the Normalized Difference Vegetation Index shows potential as a drought indicator in summer months. Both observations and simulations indicate a regime where, except in some summer months, evapotranspiration controls soil moisture. CLM simulations with different soil texture assignments show discharge sensitivity to soil moisture, but almost no impact on evapotranspiration and other energy balance components. The observed and simulated water budgets show a similar partitioning. However, the SCAN observed water balance does not close because of precipitation measurement errors, unobserved irrigation, lack of specific storage change measurements and errors in the computed actual evapotranspiration. The simulated heat flux partitioning differs from that ‘observed’, with a larger (resp. smaller) fraction of net radiation being used by latent (resp. sensible) heat flux, and unobserved freeze and thaw events. The comparison between observations and model simulations suggests that a consistent observation collection for multiple variables would be needed to constrain and improve the full set of land surface variable estimates. Copyright © 2010 John Wiley & Sons, Ltd. |
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| Keywords: | water balance energy balance SCAN land surface model NDVI MODIS actual evapotranspiration soil moisture |
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