Meteorological potential for contamination of arctic troposphere: Boundary layer structure and turbulent diffusion characteristics

Abstract

Since turbulent diffusion effects mixing and dry deposition of pollutants, characteristics of turbulence are important in understanding aerosol build up in the Arctic during the winter and early spring. This paper describes the atmospheric boundary layer (ABL) vertical and horizontal structure, turbulent heat and vapor fluxes and diffusion characteristics, obtained over pack ice, cracked ice and open water during Joint German-Russian airborne studies in March-April 1994. The turbulent fluxes of heat and water vapor were calculated with the eddy correlation method. The results showed that even a small crack in the pack ice considerably changed the heat and moisture balance of the low ABL, destroying the temperature inversion and unleashing moderate turbulence there. The coefficient of turbulent diffusion ( K L) was found to be 1 m 2/s over pack ice with a temperature inversion and 4 m 2/s over open waters. The largest loss of aerosol loading estimated from the derived K L values occurs during transport over open sea, while the smallest takes place over cracked ice. After 5 days of travel over pack ice the air mass retains less than 1 3 of initial pollution. This suggests that a local pollution source in the Arctic can contribute to the Arctic Haze only in its neighborhood. The K L values were also used to specify the rate and velocity of ozone deposition to pack ice surface. The latter had been unclear though ozone was likely to play an important role in arctic aerosol formation through SO 2 and NO x oxidation. The ozone deposition velocity to the pack ice was found to be an order of magnitude smaller than that in the middle latitudes.