A COMPARISON OF BOWEN-RATIO AND EDDY-CORRELATION SENSIBLE AND LATENT-HEAT FLUX MEASUREMENTS ABOVE DECIDUOUS FOREST

Sensible and latent heat flux densities (H and lambda E) were measured above a mature, 18 m deciduous forest during July and August, 1988, u sing the Bowen ratio - energy balance (BREB) and eddy correlation (EC) methods. EC estimates of H and lambda E underestimated day-time surfa ce available energy by 11%. EC also partitioned available energy diffe rently than BREB. For z(')/L < 0.0, EC favoured H and BREB favoured la mbda E. Practical and theoretical limitations of the BREB and EC metho ds above forests are discussed. The most plausible causes for the fail ure of EC to close the surface energy balance are a low frequency loss of flux and the failure of a single point measurement to account for the spatial dispersive flux. The most plausible causes of the EC-BREB energy partitioning anomaly are the invalidity of the BREB similarity assumption and the violation of flux-gradient diffusion assumptions in the near-field diffusion region.