In modelling evapotranspiration, the need for land surface variables including ground heat fluxes (G), surface temperature (Ts), surface relative humidity (RHs) and surface resistance often present a challenge due to land heterogeneity and limited measurements. This study introduces a simple formulation rooted in the shared physical basis of the maximum entropy model (MaxEnt), the Relative Humidity at Equilibrium (ETRHEQ) method, and the Surface Flux Equilibrium (SFE) method, and it estimates sensible (H) and latent fluxes (LE) in wetlands without requiring land surface variables or site-specific calibration, except for an assumed vegetation height. Further, it effectively estimates LE from half-hourly to monthly scales in FLUXNET and AmeriFlux wetland sites. While its performance in estimating H is less satisfactory due to loosely constrained boundary conditions, it shows promising potential for simultaneously and precisely estimating LE, H, G, Ts, and RHs from weather data in various ecosystems.

A document by Yi Wang. Click on the document to view its contents.

Peatland microtopography contains hummocks (local high points) and hollows (local low points). Little is known about how the evapotranspiration (ET) of peat (P), peat-bryophyte (BP), peat-litter (LP) and peat-bryophyte-litter (LBP) columns varies with peatland microforms. That is, whether there are fine-scale variations in peatland evaporation, and if they are critical when being upscaled to the entire peatland ecosystem is yet to be answered. This study found that ET was significantly affected by cover type (P, BP, LP or LBP) and the interaction effect of the cover type and microform, based on the field evaporation experiments in a montane peatland in the Canadian Rocky Mountains, during the growing season of 2021. Mean daily ET of P-Hummock and P-Hollow is 14.16 and 11.76 g d -1, respectively; BP-Hommock and BP-Hollow is 9.57 and 14.38 g d -1, respectively; LBP-Hummock and LBP-Hollow is 9.44 and 9.91 g d -1, respectively; and evaporation of LP-Hummock and LP-Hollow is 5.68 and 7.64 g d -1, respectively. Peatland microform indirectly affected ET through interactions with cover type, modifying the vertical profile of soil temperature, and changing key environmental drivers of evaporation. Moreover, the ability of two widely used models in modelling the spatial variation of peatland evaporation were also tested. It was found that Penman-Monteith (P-M) model and the bryophyte layer model in the Atmosphere-Plant Exchange Simulator (APES) were able to yield satisfactory results based on field measurements of soil temperature and soil moisture. This study supports developing more practical evaluation tools on the hydrological state of peatland ecosystems.