University of Twente Student Theses
Evaluating parameterizations of aerodynamic resistance to heat transfer in crop canopies towards better detection of drought stress; A case study using micro-meteorological measurements at plot-level (Barrax, Spain) and meteorological measurements at regional-level (Mashonaland West, Zimbabwe) using a crop growth simulation model.
Muchada, Patience Alice Ngaatendwe (2010) Evaluating parameterizations of aerodynamic resistance to heat transfer in crop canopies towards better detection of drought stress; A case study using micro-meteorological measurements at plot-level (Barrax, Spain) and meteorological measurements at regional-level (Mashonaland West, Zimbabwe) using a crop growth simulation model.
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| Abstract: | Parameterizations of aerodynamic resistance to heat and water transfer have a significant impact on the accuracy of models of land atmosphere interactions and estimated surface fluxes for effective account of evapotranspiration and hence accuracy in drought monitoring. The present study aims to evaluate seven popularly used parameterizations of aerodynamic resistance to heat transfer (rah) to see the effect, if any, of parameterization choice on detecting crop stress. Micro-meteorological measurements at plot-level taken over a ten-day period on the heterogeneous surface of a multi – crop Agricultural test site in Barrax, Spain were used as input into the energy balance equation and used to test the performance of the different rah parameterizations. In an extension to a larger spatial and temporal extent, meteorological measurements at regional-level (Mashonaland West, Zimbabwe) were used within a crop growth simulation model to test the same rah parameterizations. In both cases, special focus was put into the definition and estimation of roughness length, z0, and displacement height, d, which were “enhanced” from the general function of canopy height estimates to leaf area index (LAI) incorporating formulations towards a better representation of foliage density properties. Hypothesis tests for homogeneity between rah parameterizations revealed a systematic difference in the estimation of aerodynamic resistance to heat transfer and sensible heat flux between parameterizations through a non –zero intercept and slope not equal to 1. Absolute performance tests of observed against simulated values yielded values of at least r2 > 0.6 for most rah for both the Barrax and Mashonaland West studies. When RMSE and bias statistics were used in tests for the effect of adding LAI, a systematic improvement in model performance was revealed with a stronger effect in the Barrax study. The combined study reveals the effect of rah parameterization choice on accuracy of evapotranspiration estimates and more importantly, the improvement of roughness length, and hence rah, parameterizations through the addition of LAI. Keywords: aerodynamic resistance, roughness length, leaf area index, micrometeorological , crop stress |
| Item Type: | Essay (Master) |
| Faculty: | ITC: Faculty of Geo-information Science and Earth Observation |
| Programme: | Geoinformation Science and Earth Observation MSc (75014) |
| Link to this item: | https://purl.utwente.nl/essays/92513 |
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