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Applicability of the bulk-transfer approach to estimate evapotranspiration from boreal peatlands.

Isabelle, Pierre-Erik; Nadeau, Daniel F.; Rousseau, Alain N.; Coursolle, Carole; Margolis, Hank A. (2015). Applicability of the bulk-transfer approach to estimate evapotranspiration from boreal peatlands. Journal of Hydrometeorology , vol. 16 , nº 4. 1521–1539. DOI: 10.1175/JHM-D-14-0171.1.

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Résumé

In northern landscapes, peatlands are widespread and their hydrological processes are complex. Furthermore, they are typically remote, limiting the amount and accuracy of in situ measurements. This is especially the case for evapotranspiration (ET), which strongly influences watershed hydrology. The objective of this paper is to demonstrate the validity of the bulk-transfer approach to estimate ET over boreal peatlands. The simplicity of the model relies on four assumptions: (i) near-neutral atmospheric conditions; (ii) wet surface; (iii) constant momentum roughness length depending on vegetation height and; (iv) constant water vapor roughness length - the last two assumptions implying a constant water vapor transfer coefficient (CE). Using eddy covariance data from three Canadian peatlands: Necopastic (James Bay, Quebec), Mer Bleue (Ottawa, Ontario) and Western Peatland (Athabasca, Alberta); this paper shows that these sites are characterized by frequent occurrences of near-neutral atmospheric conditions, especially the Necopastic site, with nearly 76% of the 30-minute data segments occurring under near-neutral stratification. Our analysis suggests these near-neutral conditions occur as a result of strong mechanical turbulence and weak buoyancy effects. The bulk-transfer approach gives promising results for 30-min and daily ET in terms of mean error and correlation, with performances similar to Penman equation, without requiring net radiation data. The accuracy of the approach is likely related to the number of near-neutral periods and the elevated position of the water table, which backs up the wet surface assumption.

Type de document: Article
Mots-clés libres: atmosphere-land interaction; boreal meteorology; heat budgets/fluxes; in situ atmospheric observations; model evaluation/performance; stability
Centre: Centre Eau Terre Environnement
Date de dépôt: 20 avr. 2018 20:20
Dernière modification: 20 avr. 2018 20:20
URI: http://espace.inrs.ca/id/eprint/3862

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