SULFUR IN PARTICLES IN ARCTIC HAZES DERIVED FROM AIRBORNE INSITU AND LIDAR MEASUREMENTS

Quantitative information is needed on arctic hazes in order to determine their effects on the radiation budget, clouds, the albedo and chemical properties of the arctic snowpack, and on ecosystems in the Arctic. Using airborne observations from lidar, and in situ measurements of particle light-scattering coefficients, aerosol size distributions and meteorological parameters, we have related backscattering measured by the lidar to the mass concentrations of particles in two mesoscale haze layers encountered in the North American Arctic. Assuming that the haze particles were composed of H2SO4 in thermodynamic equilibrium with the ambient air, good agreement is obtained between sulfur concentrations measured on filters and those derived from the particle size distributions and lidar measurements. Time-height cross sections are shown of the airborne concentrations of sulfur in particles derived from lidar backscatter measurements in a haze layer. The average concentrations of sulfur in accumulation mode particles in the two haze layers were 0.3 and 0.4-mu-g m-3, and the maximum concentration was approximately 3-mu-g m-3, with substantial horizontal and vertical variability. We estimate lower limits for the total sulfur in particles in the two haze layers to be approximately 3X10(4) and approximately 1X10(5) kg, respectively.