Spatial and Temporal Variations of Tropospheric Aerosol Volume Distributions

Abstract

This is the second of two papers based on extensive airborne measurements of particle size distributions, taken within the lower troposphere at nine sites in western Europe. The first paper focused on the behavior of the volume (mass) mode measured in the particle radius range 0.25?0.49 ?m and its relationship to the measured volume scattering coefficient. In this paper, volume distribution plots for particle radii 0.25?5.9 ?m are shown to consist of three distinct modes, each of which is well fit by a log-normal distribution. The log-normal fit parameters do not all appear to be independent variables, but are predictable. Patterns in the behavior of the volume modes and their combinations are discussed as a function of altitude, season, relative humidity and site of measurement.