Environmental factors affecting the accuracy of surface fluxes from a two-source model in Mediterranean drylands: Upscaling instantaneous to daytime estimates

Finally, two extrapolation methods to obtain daytime (Rn > 55 W m−2) turbulent fluxes from the 15-min estimates of TSM were compared: (i) assuming the self-preservation of the evaporative and the non-evaporative fraction (EF and NEF method) and (ii) averaging the total daytime instantaneous fluxes (Averaging method). Despite the assumption of daytime self-preservation of EF and NEF was showed consistent, this method retrieved less accurate daytime estimates of H, and E than the Averaging method as a result of inaccuracies affecting estimates of EF and NEF from the TSM at our site. Moreover, better daytime estimates of H and E were obtained when using instantaneous fluxes from the TSMP than from the TSMS. Thus, reliable daytime estimates of H were obtained from the TSMP in a Mediterranean dryland, with mean errors of 20% and high correlations (R2 = 0.85). However, daytime E was strongly overestimated (125%) using the TSM by both methods, although a good correlation with eddy covariance measurements was found (R2 = 0.84).