SCALING-UP FLUX MEASUREMENTS FOR THE BOREAL FOREST USING AIRCRAFT-TOWER COMBINATIONS

Fluxes of carbon dioxide, water vapor, sensible heat, and momentum obt ained over the boreal forest from the Twin Otter aircraft and six towe r-based systems are compared. These measurements were collected as par t of the Boreal Ecosystem Atmosphere Study (BOREAS) during three inten sive field campaigns between May 25 and September 17, 1994. The repres entativeness of the tower-based measurements collected during BOREAS i s discussed. Even though the net radiation from aircraft-and tower-bas ed systems agreed well, in general, the aircraft tended to observe lar ger latent heat and smaller sensible heat fluxes than the towers. The CO2 fluxes from the aircraft were substantially less than from the tow er, while the differences were relatively small for the momentum fluxe s. The relationships between aircraft and tower-based flux measurement s obtained by making repeated runs past various towers are used to sca le up tower-based fluxes to a 16 x 16 km(2) area near Prince Albert, S askatchewan. It is demonstrated that except for a couple of cases prim arily due to rapidly changing radiation conditions, this combination o f measurements provides regional flux estimates of momentum, CO2, and sensible and latent heat similar to those obtained by flying a grid pa ttern over the area.