Results of a Comprehensive Atmospheric Aerosol-Radiation Experiment in the Southwestern United States Part I: Size Distribution, Extinction Optical Depth and Vertical Profiles of Aerosols Suspended in the Atmosphere

Abstract

An exploratory field experiment was undertaken to determine the practicality of a method specifically designed to obtain the optical properties of aerosols as they relate to the earth's radiation balance. The method requires a basic set of data consisting of the vertical distribution of aerosol concentrations, size distribution, optical depth, and net radiation fluxes. From these data radiation absorptions are determined, and effective aerosol refractive indices consistent with the actual absorption are deduced through the application of precision radiative transfer calculations. The results of 11 experiment episodes involving a combined aircraft and surface-based measurement system are described. The episodes took place in an arid desert region located near Blythe, California, and in a semiarid agricultural region located near Big Spring, Texas. Part I deals with the physical-numerical depiction of such aerosol properties as optical depth, size distribution, and vertical profiles of concentration. Part II will deal with the analysis of measurements of the radiation field leading to the deduction of the effective aerosol refractive index compatible with the absorption of solar radiation.