The role of ground heat flux in estimating evapotranspiration by the Penman-Monteith method on mountain meadow

Michal Dohnal, Jana Votrubová, Rebeka Mazúchová and Miroslav Tesař
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Michal Dohnal: Faculty of Civil Engineering, Czech Technical University in Prague, Prague, Czech Republic
Jana Votrubová: Faculty of Civil Engineering, Czech Technical University in Prague, Prague, Czech Republic
Rebeka Mazúchová: Faculty of Civil Engineering, Czech Technical University in Prague, Prague, Czech Republic
Miroslav Tesař: Institute of Hydrodynamics of the Czech Academy of Sciences, Prague, Czech Republic

Soil and Water Research, vol. preprint

Abstract: Ground heat flux (G) is often an overlooked component of the surface energy balance, and its accurate determination remains challenging. In the present study, the accuracy of various G estimation methods is examined using long-term measurements from the Central European mountain meadow. The impact of different G approximation on calculated evapotranspiration by the Penman-Monteith method (ET) is analysed. Soil heat flux measurements and surface temperature data were used to determine G, while net radiation was used to approximate G. Neglecting G led to an overestimation of ET in the daily timestep. On the contrary, the FAO-recommended hourly approximation overestimated G, underestimating ET. Site-specific calibrations of G prediction models improved their accuracy. For daily average G, as well as for hourly average G, simple constant parameter models (i.e., models including a single parameter specifying the fraction of net radiation directly) provide satisfactory accuracy of ET evaluation. However, in an hourly timestep, net radiation fails as a predictor of G shortly after sunrise and before sunset. The findings emphasise the importance of considering G in ET calculations and the need for site-specific calibrations of G estimation models.

Keywords: evapotranspiration of grass; Penman-Monteith equation; sandy loam texture; soil heat flux; soil temperature (search for similar items in EconPapers)
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Persistent link: https://EconPapers.repec.org/RePEc:caa:jnlswr:v:preprint:id:24-2025-swr

DOI: 10.17221/24/2025-SWR

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