Evapotranspiration from a wetland tundra sedge fen: Surface resistance of peat for land-surface schemes

Eddy covariance measurements of evapotranspiration at a wetland tundra sedge fen near Churchill, Manitoba, Canada, from 15 June to 21 August, 2007, were used to calculate hourly resistance values for the peat component of the fen’s surface. Inherent in the calculations were the assumptions that evaporation from the open water and transpiration from the living sedge components of the fen’s surface, as well as the aerodynamic resistance, could be reasonably well modeled. Fitting a curve to these results provided a regression model for the daytime variation of the hourly surface resistance to evaporation from the peat. It was concluded that the surface resistance, which was relatively low during the morning hours and increased during the afternoon hours, reflected, in part, a diurnal wetting and drying of the near surface layer. This insight into the daytime variation of resistance to evaporation from the peat surface of a wetland tundra sedge fen may be of assistance in the formulation of land-surface schemes.