Accession Number : ADA130998

Title :   Measurements of Atmospheric Aerosols: Experimental Methods and Results of Measurements off the East Coast of the United States.

Descriptive Note : Interim rept.,


Personal Author(s) : Hoppel,William A ; Fitzgerald,James W ; Larson,Reginald E

PDF Url : ADA130998

Report Date : 19 Jul 1983

Pagination or Media Count : 71

Abstract : Accurate measurements of the size distribution of atmospheric aerosols in the size (radius) range from 0.006 to 2.2 micrometers made along the east coast of the United States--both at a shore site (Wallops Island) and from a ship within 300 km of the coast--are presented. Some measurements at Washington, D.C., are included to contrast urban aerosols with aged continental air off the east coast. As air advects from land to sea, there is a rather rapid decay of particles smaller than 0.05 micrometers during the first day or so. After this initial decay of small particles the size distribution was often found to remain remarkably stable for hours. Significant changes in the size distribution were often associated with changes in air masses and meteorological conditions. Some of the changes can be explained qualitatively. Others, such as a pronounced double peak which occurred occasionally in the fine-particle range, are difficult to understand. Measurements of the activation parameter for submicrometer particles were also made and yield values in the range of 0.1 to 0.55. Using the measured size distribution, electromagnetic extinction was calculated for the wavelength range 0.3 to 12 micrometers. The calculations compare favorably to the measured scattering coefficient at 0.55 micrometers in wavelength. Particles in the radius range 0.1 to 0.3 micrometer made the largest contribution to the total extinction at optical wavelengths on nearly all occasions.

Descriptors :   *Aerosols, *Visibility, Particle size, Measurement, Statistical distributions, Spatial distribution, Marine atmospheres, Advection, Earth atmosphere, Urban areas, Air mass analysis, Coastal regions, United States, Shipboard, Electromagnetic radiation, Extinction, Electromagnetic scattering, Condensation nuclei, Fines, Solubility

Subject Categories : Atmospheric Physics
      Test Facilities, Equipment and Methods
      Radiofrequency Wave Propagation

Distribution Statement : APPROVED FOR PUBLIC RELEASE