THE VERTICAL-DISTRIBUTION OF AEROSOLS AND ACID RELATED-COMPOUNDS IN AIR AND CLOUDWATER

Vertical profiles (surface to 5 km) of aerosol particle number concentration, NO'(y) mixing ratio, and cloudwater SO4(2-) and NO3- equivalent concentration were obtained in three field studies: North Bay, Ontario, during the summer of 1982 and the winter of 1983-1984, and Syracuse, New York, during the fall of 1984. The measurements from these locations and different seasons are compared. Generally, airborne concentrations are highest with air-mass back trajectories from the south and lowest with back trajectories from the north. For the southerly trajectories, median particle number concentrations (0.2-2 mu-m) near ground level (950 mb) vary from 1700 cm-3 during the summer project to 800 cm-3 during the winter project. At 700 mb, the south trajectory particle number concentration ranged between 60 and 170 cm-3. Median NO'(y) mixing ratios for southerly back trajectories were approximately 6 and 9 ppb at 950 mb and 0.4 and 0.8 ppb at 700 mb for the fall and winter projects, respectively. Comparison of particle number concentrations profiles outside of cloud with cloud droplet plus interstitial aerosol particle number concentrations inside cloud indicate that cumulus clouds can transport aerosols vertically from below cloud base. In contrast, stratiform clouds have similar concentrations inside the clouds as outside at the same altitude. The vertical variations of cloudwater sulphate and nitrate concentrations and the NO3-/SO4(2-) equivalent concentration ratio are discussed for each of the three field studies.