Geoscience Reference
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where t 0 is the time shift parameter, and the subscripts d and i refer to daily and instantaneous
(say in practice, hourly or half-hourly) variables, respectively; F d is the average flux on day
t d of some other flux term (beside the latent heat flux) in the surface energy budget, which
can be assumed to exhibit a similar diurnal variation as the evaporation rate; F i is that flux
at time t = t i of the same day. Thus Equation (9.114) contains two time scales, t d in units
of days, and t i in units of hours. As illustrated in Figure 9.29, by assuming F = R n G
this formulation was able to reproduce daytime hourly flux values over a period of 2 weeks
during the second stage of drying already considered in Example 9.4. The approach was
subsequently applied again and validated in a different experiment by Porte-Agel et al .
(2000), who obtained similar results. Under the right circumstances, the approach based on
Equation (9.114) may be useful in the disaggregation of daily, or even weekly, evaporation
into hourly values, when more complete information is lacking.
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