Mixture of Time Scales in Evaporation: Desorption and SelfSimilarity of Energy Fluxes
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The time evolution of evaporation from a bare soil, over a 9-d period following irrigation, is described by a combination of daily and hourly drying patterns. From the second day, the daily evaporation shows a second stage of drying that can be described as a desorptive process (evaporation proportional to (t - t0)(-1/2), where t is time in days and t0 is the day when the second stage starts). The short time (hourly) evaporation rate can be modeled on the basis of a type of self-similarity in the energy balance components. Combining the evaporative flux behavior at the two time scales, desorption at the daily timescale and self-similarity for the diurnal variations, a robust description of evaporation for drying land surfaces is obtained. This approach is tested using accurate measurements of the different components of the energy balance at the soil surface, obtained at 20-min intervals. The model accurately describes the time evalution of the evaporative flux and could be used for the disaggregation of daily or weekly evaporation into hourly values.
author list (cited authors)
PortAgel, F., Parlange, M. B., Cahill, A. T., & Gruber, A.