Large particle characteristics over the southern ocean during ACE 1

• Main Authors: Davis, Janel T., author, Kreidenweis, Sonia M., author
• Format: Text
• Language: English
• Published: Colorado State University. Libraries 2022
• Subjects: Cloud physics; Ocean-atmosphere interaction; Southern Ocean
• Online Access: https://hdl.handle.net/10217/234503

December 1998. Also issued as Janel T. Davis's thesis (M.S.) -- Colorado State University, 1998. The Aerosol Characterization Experiment (ACE-1) in November and December 1995 was designed to characterize aerosol physical, chemical, and optical properties in remote marine regions in the Southern Hemisphere. Data from six ACE-1 research flights were used to examine concentrations of large particles in two size ranges: those having diameters, Dp, 0.5 Dp 50 µm (N1) and those with 2.0 Dp 50 µm (N2). Reported here are observations of vertical profiles of N1 and N2 for heights, z, from ~30 to 7000 mover the ocean surface. Number concentrations near the surface (z 900 m) varied from 0.8 to ~30 cm-3, while maximum N2 concentrations were ~ 2.0 cm-3. Above altitudes of 2400 m, N1 concentrations were found to vary from greater than 0.07 to 1.2 cm-3. Significant concentrations (> 0.02 cm-3) of N2 particles aloft were usually associated with regions of deep convection, cloud outflow, and cloud dissipation. Calculated dry mass concentrations for N1 particles near the surface (z 100 m) assumed to be primarily sea salt, showed dependence on wind speed. Computed dry sea salt mass concentrations varied from 2.0 to 30.0 µg m-3 and varied with wind speed similarly to previously proposed relationships. Aerosol size distributions were used to compute particle light scattering coefficients and aerosol visible optical depths. The light scattering coefficient for N1 particles ranged from 0.002 to 0.08 1an-1 at altitudes less than 900 m, and from 0.00005 to 0.05 km·1 at higher altitudes. For N2 particles, the light scattering coefficient ranged from 0.001 to 0.05 km-1 for z < 900 m and from 0.0003 to 0.04 km-1 for z > 900 m. The large particles are a significant contribution to the total aerosol light scattering coefficient. Optical depths for these particles ranged from 0.043 to 0.085 for N1 and from 0.019 to 0.039 for N2. Sponsored by the National Science Foundation (NSF), Significant Opportunities in Atmospheric Research ...