Comparison of standard and actual crop evapotranspiration estimates derived from different evapotranspiration methods on the Canadian Prairies
✍ Scribed by M. Gervais; M. Mkhabela; P. Bullock; R. Raddatz; G. Finlay
- Publisher
- John Wiley and Sons
- Year
- 2011
- Tongue
- English
- Weight
- 580 KB
- Volume
- 26
- Category
- Article
- ISSN
- 0885-6087
- DOI
- 10.1002/hyp.8279
No coin nor oath required. For personal study only.
✦ Synopsis
Evapotranspiration (ET) models have become essential tools in areas such as climate modelling, weather forecasting, crop yield forecasting and irrigation planning. The modified second-generation Prairie Agrometeorology Model (PAMII 1C2 ) estimates standard ET (ET c ) (i.e. evapotranspiration from disease free, well fertilized crops, grown under optimum soil water conditions) by simulating crop development and the soil water balance using daily minimum and maximum surface air temperature, rainfall and upper air conditions to simulate the depth of the planetary boundary layer. The FAO56 Penman-Monteith (FAO56 P-M) method uses a reference surface/combination approach to calculate reference ET (ET o ) and then multiply it by a crop coefficient (K c ) to derive ET c . The simplified water balance (WB) method estimates actual ET (ET a ) as the residual of the water balance where precipitation and soil water variation are known. The objective of this study was to compare both ET c and ET a estimates from PAMII 1C2 to those derived using the FAO56 P-M and the water balance models.
Comparison of daily ET rates between PAMII 1C2 and the FAO56 P-M method indicated significant differences in the ET c (RMSD D 1Ð88 mm d 1 , r 2 D 0Ð45) and ET a (RMSD D 1Ð65 mm d 1 , r 2 D 0Ð45). When compared to the WB derived weekly and biweekly total ET c , PAMII 1C2 produced similar rates of ET a (r 2 D 0Ð62, slope D 0Ð65), as the FAO56 P-M (r 2 D 0Ð61, slope D 0Ð50) model. Both models produced overall ET a rates that fell within the range of the measurement error associated with the WB method. Since PAMII 1C2 produced similar ET c and ET a rates compared to the FAO56 P-M method, for any potential user the choice between the PAMII 1C2 and FAO56 P-M is less a matter of accuracy and more a function of the type of input data available.