|Evett, Steven - Steve|
Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 7/5/2000
Publication Date: N/A
Technical Abstract: The Bowen ratio-energy balance (BREB) is a micrometeorological method often used to estimate latent heat flux because of its simplicity, robustness, and cost. BREB estimates have compared favorably with other methods in several studies, but other studies have been less certain, especially when there was sensible heat advection. We compared latent heat flux of irrigated alfalfa (Medicago sativa, L.) estimated by the BREB method with that measured by large, precision, weighing lysimeters in the semiarid, advective environment of the Southern High Plains. Root mean square difference (RMSD) and indicators of sensible heat advection were used to analyze the performance of the BREB method relative to lysimeters. Relative RMSD (normalized by mean lysimeter latent heat flux) between lysimeter and BREB latent heat fluxes averaged 25 to 29% during the first two alfalfa harvest periods and decreased to 16 to 19% during the last three harvest periods of the season. Greatest differences between the two methods were measured when there was evidence of sensible heat advection. Relative RMSD increased as the Bowen ratio became more negative; as hot, dry, and windy conditions increased; or as the ratio of latent heat flux to available energy increased.