FORMULATION OF SURFACE HEAT-FLUX - APPLICATION TO BOREAS

The aerodynamic temperature is required for prediction of the surface heat flux using Monin-Obukhov similarity. This ''fictitious'' temperat ure is not systematically equal to the actual air temperature near the surface and is not directly available from observations or in numeric al models, The aerodynamic temperature is normally replaced with eithe r the canopy air temperature or the surface radiation temperature, som etimes accompanied by adjustment of the thermal roughness length or sp ecification of an excess resistance, In this study, the relationship b etween the aerodynamic temperature and the surface radiation temperatu re is examined in terms of the surface energy budget and simple repres entation of canopy structure. Previous inconsistencies are discussed. The observed behavior of the aerodynamic temperature is studied using Canadian Twin Otter aircraft data from BOREAS over nine different fore sted and nonforested sites. Variation of the behavior of the aerodynam ic temperature between different parts of the boreal forest is found t o be strongly correlated with the red reflectance.