Long-term measurements of surface fluxes above a Scots pine forest in Hyytiälä, southern Finland, 1996–2001

Abstract

We present nearly six years of measurements of surface fluxes of momentum, sensible heat, water vapour, carbon dioxide and aerosol particles, along with a three-month time series of ozone flux, measured by eddy covariance above a Scots pine forest in southern Finland from April 1996 to December 2001. The results show marked seasonal and diurnal variation and a significant effect of local and remote anthropogenic pollution on CO₂ and particle data. The flux of inert CO₂ followed environmental factors through plant and soil-microbe metabolism very closely. The flux of reactive O₃ depended on the overlapping influences of environmental parameters driving photosynthesis and of the available amount of reaction partners. The flux of multireactive aerosol particles showed no clear connection with any environmental variable. On new-particle-formation days, the average deposition velocity of particles was, however, greater than usual because small nucleation-mode particles have greater deposition velocities than do larger accumulation-mode particles.