Validation of et estimates from the canadian prairie agrometeorological model for contrasting vegetation types and growing seasons

Abstract

The objective of this study was to establish the ability of the prairie agrometeorological model (PAMII) to simulate daily evapotranspiration (ET). Specifically, modelled ET estimates from PAMII were validated using daily ET estimates from eddy-covariance systems at West Nose Creek (barley field located northwest of Calgary, Alberta) and a FluxNet site (short-grass prairie located west of Lethbridge, Alberta). Additionally, PAMII was validated for three contrasting growing seasons at the grassland site to establish the model's ability to quantify the effect of different growth conditions on ET. PAMII performed well and was able to capture the day-to-day variability of the ET at both sites. PAMII successfully captured the increase (decrease) in accumulated growing season ET for the wet (dry) growing seasons at the short-grass prairie site. Moreover, the optimal reference minimum stomatal resistance term was significantly lower for the barley crop (50 s m-1) than the corresponding value for the short-grass prairie (80 s m-1). At the grassland site the optimal stomatal resistance term varied markedly depending on the growing conditions; the optimal value for the wet year was 60 s m -1 compared to 90 s m-1 for the dry year. That is, no single value worked best for all years, and our findings caution against using a single value for the reference minimum stomatal resistance. In summary, PAMII captured the salient features of the ET variability at both sites and for contrasting at the grassland site. However, our research has identified several areas where future versions of the PAMII model might be improved. © 2010 Canadian Water Resources Association.