Long-range transport of biomass burning smoke to Finland in 2006

Abstract. Finland experienced extraordinary smoke episodes in 2006. The smoke was measured at the three SMEAR measurement network stations in Finland after it had been transported several hundreds of kilometers from burning areas in Eastern Europe. A trajectory method combining MODIS fire detections and HYSPLIT trajectories enabled us to separate the effect of biomass burning smoke from the measured concentrations and also study the changes in the smoke during its transport. The long-range transported smoke included at least NO_x, SO₂, CO₂, CO, black carbon and fine aerosol particles, peaking at 100 to 200 nm size. The most reliable smoke markers were CO and SO₂, especially when combined with particle data, for which black carbon or the condensation sink are very effective parameters separating the smoke episodes from no-smoke episodes. Signs of fresh secondary particles was observed based on the particle number size distribution data. While transported from south to north, particles grew in size, even after transport of tens of hours and several hundreds of kilometres. No new aerosol particle formation events were observed at the measurement sites during the smoke periods.