A modified Bowen ratio method to determine sensible and latent heat fluxes

The sensible heat flux (H) and the latent heat flux (lambdaE) were measured above a grassland during June, 1997 (LINEX-97/1 Experiment), using the edd y covariance method (EC) and the Bowen ratio/Energy balance method (BREB). The results indicate that H-BREB is about (30 +/- 20) W m(-2) higher than H -EC. and lambdaE(BREB) is about (180 +/- 40) W m(-2) higher than lambdaE(EC ) during the daytime, and this is mainly caused by an imbalance in the clos ure of the surface energy balance in the BREB. In order to avoid the inaccu racies associated with the surface energy balance method, we propose a modi fied Bowen ratio method (MBR) to determine sensible and latent heat fluxes without using the surface energy balance equation. The results and error an alysis show that MBR can give more accurate results than BREB. For the MBR, a measurement system using a sonic anemometer together with temperature an d humidity measurements at two levels is being recommended to obtain sensib le and latent heat fluxes.