Summary
Accurate measurements of thermal conductivity and diffusivity, made both at soil surface by a flat heater and at various depths by cylindrical heat sources, had allowed a better estimation of soil heat flux. It was seen that heat flux is an important component in the energy balance for a bare soil over a short time interval (as 1 hr): indeed, when the driving force of evaporation is active and soil water content is low, heat flux may reach the peak value of 25 percent of net radiation, and, when the evaporative heat is zero, it may reach a value slightly more than 40 percent (generally, this is noted few hours after sunrise or before sunset). Subsequently, the estimate of the evaporative heat by energy balance is more realistic if the value of soil heat flux is not ambiguous, provided that all other components are known or measurable.
Zusammenfassung
Genaue Messungen der thermischen Leitfähigkeit und der Diffusion, die auf der Boden-oberfläche mit einer flachen Heizquelle und in verschiedenen Tiefen mit zylindrischen Wärmequellen durchgeführt worden sind, haben eine bessere Schätzung des Wärmeflusses im Boden ermöglicht. Es wurde festgestellt, daß der Wärmefluß eine wichtige Komponente der Energiebilanz in einem aperen Boden über ein kurzes Zeitintervall hinweg (1 Stunde) ist. Tatsächlich kann, wenn Verdunstung auftritt und der Bodenwassergehalt gering ist, der Wärmefluß einen Spitzenwert von 25% der Strahlungsbilanz erreichen und, wenn die Verdunstungswärme Null ist, kann er einen Wert etwas über 40% erreichen (dies ist im allgemeinen wenige Stunden nach Sonnenaufgang oder vor Sonnenuntergang der Fall). Folglich ist die Schätzung der Verdunstungswärme aus der Energiebilanz mehr realistisch, wenn der Wert des Wärmeflusses in Boden nicht unsicher ist, vorausgesetzt, daß alle anderen Komponenten bekannt oder meßbar sind.
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Zito, G., Mongelli, F. & Loddo, M. Influence of accurate heat flux measurements on the evaluation of evaporation from a bare soil by energy balance. Arch. Met. Geoph. Biokl. A. 27, 155–169 (1978). https://doi.org/10.1007/BF02246692
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DOI: https://doi.org/10.1007/BF02246692