Effect of stability correction on remote sensing estimates of near‐noon sensible heat flux of alfalfa and tall fescue grass

Abstract

Sensible heat flux (H) can be an important component of the energy balance of earth surfaces, especially under dry soil conditions and incomplete canopy cover. Estimating H from remote sensing often requires correcting for atmospheric stability to account for the effect of buoyancy, and several simplified methods have been used to make this correction. In this study, data collected from alfalfa and tall fescue grass fields at Kimberly, Idaho, were used to: (1) determine how near‐noon values of stability‐corrected aerodynamic resistance for heat transfer (r ahc) calculated with seven different methods compared with those obtained using a standard micrometeorological method, (2) determine whether the method used to calculate r ahc had a significant effect on near‐noon H calculated using a remote sensing resistance model, and (3) assess the validity of the remote sensing model for determining near‐noon H. It was found that discrepancies in r ahc between methods, compared with the standard method, increased for low wind speeds (u 2) (u 2<2 m s−1), and there was good agreement for five of the seven methods compared for u 2>2 m s−1. Those five methods also had good agreement with the standard method when they were used to calculate near‐noon H for both surfaces. The agreement was good even for low u 2, despite the disagreement in r ahc at low u 2. The other two methods were well correlated with the standard method, but showed significant bias. It was also found that near‐noon H values obtained from remote sensing were well correlated with Bowen ratio measurements but were statistically different from each other for both surfaces.