RELATIONSHIP OF SURFACE HEAT-FLUX TO MICROSCALE TEMPERATURE-VARIATIONS - APPLICATION TO BOREAS

The surface heat flux is normally parameterized in terms of the differ ence between the air temperature and the surface radiative temperature , or equivalently, the temperature computed from the surface energy ba lance. In this note, the relationship between the heat flux and the ai r-surface temperature difference is shown to be sensitive to the micro scale variability of the surface radiation temperature caused by diffe rences between the well-ventilated tree tops and less ventilated groun d surface. This conclusion is based on surface and aircraft data colle cted during the Boreal Ecosystem-Atmosphere Study (BOREAS). For this c ase, the heat flux cannot be predicted by adjusting the thermal roughn ess height. As an alternative, the aerodynamic temperature can be rela ted to a weighted average of the surface radiation temperature analogo us to application of a simple canopy model. Here, the total heat flux is the sum of the heat fluxes from each individual surface type weight ed by the area-fractional coverage.