Evapotranspiration models of different complexity for multiple land cover types

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Hydrological Processes


A comparison between half-hourly and daily measured and computed evapotranspiration (ET) using three models of different complexity, namely, the Priestley-Taylor (P-T), the reference Penman-Monteith (P-M) and the Common Land Model (CLM), was conducted using three AmeriFlux sites under different land cover and climate conditions (i.e. arid grassland, temperate forest and subhumid cropland). Using the reference P-M model with a semiempirical soil moisture function to adjust for water-limiting conditions yielded ET estimates in reasonable agreement with the observations [root mean square error (RMSE) of 64-87Wm -2 for half-hourly and RMSE of 0.5-1.9mmday -1 for daily] and similar to the complex Common Land Model (RMSE of 60-94Wm -2 for half-hourly and RMSE of 0.4-2.1mmday -1 for daily) at the grassland and cropland sites. However, the semiempirical soil moisture function was not applicable particularly for the P-T model at the forest site, suggesting that adjustments to key model variables may be required when applied to diverse land covers. On the other hand, under certain land cover/environmental conditions, the use of microwave-derived soil moisture information was found to be a reliable metric of regional moisture conditions to adjust simple ET models for water-limited cases. Further studies are needed to evaluate the utility of the simplified methods for different landscapes. © 2011 John Wiley & Sons, Ltd.

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