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United States Department of Agriculture

Agricultural Research Service

Title: Energy Balance and Water and Heat Transfer Simulated by Shaw and Rz-Shaw

Authors
item Yu, Qiang - CHINESE EXPER. STATION
item Kozak, Joseph
item Xu, Shouhua - CHINESE EXPER. STATION
item Flerchinger, Gerald
item Ma, Liwang
item Ahuja, Lajpat

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: May 19, 2005
Publication Date: November 10, 2005
Citation: Yu, Q., Kozak, J.A., Xu, S., Flerchinger, G.N., Ma, L., Ahuja, L.R. 2005. Energy balance and water and heat transfer simulated by shaw and rz-shaw. ASA-CSSA-SSSA Annual 2005 Meeting Abstracts. Salt Lake City, UT. Nov. 6-10, 2005.

Interpretive Summary: RZ-SHAW is a new hybrid model coupling the Root Zone Water Quality Model (RZWQM) and the Simultaneous Heat and Water (SHAW) Model to extend RZWQM applications to conditions of frozen soil and soil surface with crop residue cover. The objective of this study was to evaluate RZ-SHAW for simulations of energy balance over plant canopies. Canopy energy balance data were collected at various growing stages of winter wheat in the North China Plain. Both RZ-SHAW and SHAW were compared for net radiation, latent heat fluxes, sensible heat fluxes, and soil heat fluxes using hourly meteorological data. RZ-SHAW provided essentially the same goodness-of-prediction as the original SHAW model for all the energy balance components when using observed plant growth input data. The average root mean square error (RMSE) for simulated net radiation, latent heat, sensible heat, and soil heat was 31.3 W m-2 for SHAW and 35.8 W m-2 for RZ-SHAW. A sensitivity analysis was performed with respect to a range of initial water content, leaf area indices (LAIs), and plant heights. Initial water contents had the most significant effect on latent heat and sensible heat fluxes, especially at lower water contents. LAI variations had the greatest effect on sensible and soil heat fluxes. Plant height had little to no effect on the surface energy balance components. Finally, an analysis was performed using the plant growth component of RZ-SHAW instead of inputting LAI, plant height, and initial water content. The model simulation results agreed with the plant height and yield very well. Overall, the results demonstrated a successful coupling of RZWQM and SHAW in terms of canopy energy balance simulation. RZ-SHAW offers a new model to simulate diurnal changes in energy balance and air temperature needed for simulating plant canopy effects on soil temperature.

Technical Abstract: RZ-SHAW is a new hybrid model coupling the Root Zone Water Quality Model (RZWQM) and the Simultaneous Heat and Water (SHAW) Model to extend RZWQM applications to conditions of frozen soil and soil surface with crop residue cover. The objective of this study was to evaluate RZ-SHAW for simulations of energy balance over plant canopies. Canopy energy balance data were collected at various growing stages of winter wheat in the North China Plain. Both RZ-SHAW and SHAW were compared for net radiation, latent heat fluxes, sensible heat fluxes, and soil heat fluxes using hourly meteorological data. RZ-SHAW provided essentially the same goodness-of-prediction as the original SHAW model for all the energy balance components when using observed plant growth input data. The average root mean square error (RMSE) for simulated net radiation, latent heat, sensible heat, and soil heat was 31.3 W m-2 for SHAW and 35.8 W m-2 for RZ-SHAW. A sensitivity analysis was performed with respect to a range of initial water content, leaf area indices (LAIs), and plant heights. Initial water contents had the most significant effect on latent heat and sensible heat fluxes, especially at lower water contents. LAI variations had the greatest effect on sensible and soil heat fluxes. Plant height had little to no effect on the surface energy balance components. Finally, an analysis was performed using the plant growth component of RZ-SHAW instead of inputting LAI, plant height, and initial water content. The model simulation results agreed with the plant height and yield very well. Overall, the results demonstrated a successful coupling of RZWQM and SHAW in terms of canopy energy balance simulation. RZ-SHAW offers a new model to simulate diurnal changes in energy balance and air temperature needed for simulating plant canopy effects on soil temperature.

Last Modified: 11/24/2014
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