Atmospheric Aerosol Size Distributions and Optical Properties Found in the Marine Boundary Layer Over the Atlantic Ocean

摘要

Measurements and analyses of the aersol size distributions and optical properties found in the marine boundary layer during the 1983 USNS Lynch cruise from Charleston SC to Scotland via Canary Islands are presented. The data given in this report are the most extensive and accurate measurements of the submicron marine aerosol size distribution to date and are supplemented by extensive meteorological observations, balloon soundings, satellite coverage, calculated air mass trajectories, and aerosol chemistry. Eight detailed case studies of the size distribution which occurred under different meteorological conditions are presented and discussed. The data indicates that repeated cycling of marine boundary layer (MBL) air through nonprecipitating clouds which are usually present at the top of the MBL is a major factor in shaping the size distribution and that new particle formation by hetermolecular, homogeneous nucleation is the most likely mechanism which sustains the concentration of particles found below 0.04 micron radius. Calculations of the scattering and extinction coefficients and optical depth of the MBL as a function of wavelength directly from the measured size distribution and MBL vertical structure are compared to measured values of the scattering coefficient and optical depth. These measured and calculated optical properties correlate well throughout the cruise and the results give a relatively consistent picture of the relationship between the aerosol size distribution and E-M properties in the MBL. Keywords: Marine atmospheres; Electromagnetic properties; Particle size. (edc)