Submitted to: Symposium on Boundary Layer
Publication Type: Proceedings
Publication Acceptance Date: August 1, 1997
Publication Date: N/A
Technical Abstract: The problem of determining the surface energy balance in an arid ecosystem is explored with flux measurements collected in the Jornada Experimental Range near Las Cruces New Mexico. The most common techniques for estimating evaporation and heat loss are the Bowen ratio and eddy covariance. The heterogeneity of such surfaces poses special problems for both the estimation and interpretation of surface fluxes of mass and energy. Gradients and temporal fluctuations in humidity are small, requiring very precise humidity measurements. These measurement techniques are valid for relatively uniform surfaces, but for these arid regions the evaporation source (the vegetation) and heat source (the bare soil) are highly spatially variable. Comparison of the Bowen ratio and eddy covariance measurements of evaporation during several intensive field studies indicate significant discrepancies can exist, especially over the more heterogeneous shrub covered surfaces. Further analysis of the data together with high resolution video remote sensing and turbulence time series data will be used to help determine factors related to differing amounts and distribution of bare soil versus vegetation cover that may be affecting the Bowen ratio and eddy covariance measurements and the theory and assumptions behind these techniques which this type of surface may violate.