Original paper
Eddy covariance observations and FAO Penman-Monteith modelling of evapotranspiration over a heterogeneous farmland area
Siedlecki, Mariusz; Pawlak, Włodzimierz; Fortuniak, Krzysztof
Meteorologische Zeitschrift Vol. 31 No. 3 (2022), p. 227 - 242
82 references
published: Jun 30, 2022
published online: Jan 26, 2022
manuscript accepted: Nov 30, 2021
final revised version received: Sep 27, 2021
manuscript revision requested: Dec 23, 2021
manuscript received: Oct 12, 2020
Open Access (paper may be downloaded free of charge)
Abstract
This work presents the characteristics of actual evapotranspiration obtained using the eddy covariance method and a comparison with the results of crop reference evapotranspiration determined based on the FAO‑56 Penman-Monteith formula. The results of measurements performed under conditions typical of Central and Southern Poland's agricultural landscape cover the years 2012–2019. The characteristics of latent heat flux ( Q e $Q_e$ ), as compared to other components of the heat balance, show its rapid growth in spring well above the value of sensible heat ( Q h $Q_h$ ). The Q e $Q_e$ values in the noon hours account for over 50 % of the available solar energy. In the summer season, the ripening of cereals and their harvesting result in quite a significant decrease in the value of Q e $Q_e$ , which entails an increase in the value of Q h $Q_h$ and an increasing value of the Bowen ratio (exceeding 1 in August). A comparison of the results of the covariance measurements with the results obtained on the basis of the FAO‑56 methodology shows that they are fairly consistent, especially in May and June, i.e. the period of high precipitation and fully developed vegetation. The average monthly values of the crop coefficient Kc, determined as the ratio of actual and reference evapotranspiration, takes values close to 1. In July, August and September, on the other hand, reference evapotranspiration is much higher than the values obtained from measurements. The determined values of Kc range between 0.7 and 0.8.
Keywords
actual evapotranspiration • eddy covariance method • FAO‑56 Penman-Monteith formula • energy partitioning • crop coefficient