A generalized Complementary Principle (GCP) Model With Atmospheric Stability Correction for Estimating Sub‐Daily Evaporation

At daily or longer time scales, the generalized complementary principle (GCP) has been shown to provide accurate estimates of evaporation from routine meteorological data. However, the validity of the complementary principle at sub‐daily timescale has not been thoroughly tested. In this study, the GCP combined with the Monin‐Obukhov similarity theory was tested for describing sub‐daily (e.g., 30 mins or hr) land surface evaporation. The analysis consists of parameter optimization and atmospheric stability correction applied simultaneously. The performance of the GCP method was evaluated against evaporation rates measured by eddy covariance‐system at two Australian flux sites under different surface and climatic conditions. The atmospheric evaporative demand or apparent potential evaporation, one of the key variables in the GCP method, was estimated using the Penman equation with atmospheric stability correction included; it was found that the effect of atmospheric instability can increase this apparent potential evaporation by up to 17% compared with that under assumed neutral conditions. The estimated sub‐daily evaporation values were in good agreement with the measurements with a mean R 2 of 0.84 and a bias of −0.60% on average. It was found that the generalized complementary relationship is valid at the sub‐daily timescale and that the effect of atmospheric stability is important for describing sub‐daily evaporation.