Estimation of area-average sensible heat flux using a large-aperture scintillometer during the Semi-Arid Land-Surface-Atmosphere (SALSA) experiment

The use of a large-aperture scintillometer to estimate sensible heat flux h as been successfully tested by several investigators. Most of these investi gations, however, have been confined to homogeneous or to sparse with singl e vegetation-type surfaces. The use of the scintillometer over surfaces mad e up of contrasting vegetation types is problematic because it requires est imates of effective roughness length and effective displacement height in o rder to derive area-average sensible heat from measurements of the refracti ve index. In this study an approach based on a combination of scintillomete r measurements and an aggregation scheme has been used to derive area-avera ge sensible heat flux over a transect spanning two adjacent and contrasting vegetation patches: grass and mesquite, The performance of this approach h as been assessed using data collected during the 1997 Semi-Arid Land-Surfac e-Atmosphere field campaign. The results show that the combined approach pe rformed remarkably well, and the correlation coefficient between measured a nd simulated area-average sensible heat flux was similar to 0.95. This is o f interest because this approach offers a reliable means for validating rem otely sensed estimates of surface fluxes at comparable spatial scales.