Characteristics of atmospheric aerosols using optical remote sensing
Document ID: 203
Philbrick, C. Russell1
Wright, Timothy1
Snyder, Michelle Grace1
Hallen, Hans D.1
Brown, Andrea M.2
Verghese, Sachin John2
Edwards, Perry S.2
1 North Carolina State University, Raleigh, NC, U.S.A.
2 The Pennsylvania State University, University Park, PA, U.S.A.
Presented: 12th Conference on Atmospheric Chemistry
Atlanta, Georgia, January 16-21, 2010
Abstract
Laser remote sensing techniques now provide important tools for determining most of the properties of aerosols, including their physical and chemical characteristics. Examples are selected to show the types of information contained in the optical scattering signatures. Improvements in our understanding the distribution of aerosols, their sources, and processes controlling their formation and growth are needed for a detail understanding of their contributions to the planetary albedo and their influence on radiative transfer. These are critically important factors for developing accurate predictions of changes to be expected in our climate.
Multi-wavelength backscatter measurements from Rayleigh and Raman lidar techniques provide signals that are used to profile the properties that govern the transmission of radiation through an atmospheric column. Rayleigh lidar signals provide backscatter coefficients, and Raman lidar signals backscattered from the major molecular components provide extinction profiles. The ratio of these simultaneous extinction and backscatter measurements are used to describe the aerosol type. In addition, a laser beam can be used to make bistatic and multistatic measurements of the polarization ratio of the scattering phase function. Analysis of multistatic measurements can be used to determine profiles of the aerosol number density, size, size distribution, and type. These parameters can be measured for spherical particles in the size range between about 20 nm and 20 μm. Analysis of the size distribution requires adopting a mathematical function, which is usually taken to be a log-normal distribution. Information on aerosol type and shape can be supposed from determining the approximate refractive index of the scattering aerosols and by measuring the depolarization of the scattered radiation.