Estimation of Aerosol Extinction-to-Backscatter Ratios using AERONET Measurements and Cluster Analysis

• Main Authors: Ali H. Omar, Jae-gwang Won, Sun-chang Yoon, M. Patrick Mccormick
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Aerosol Robotic Network
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.522.1157; http://www-calipso.larc.nasa.gov/resources/pdfs/NEW_4.12.05/Omar - 21stILRC_S121.pdf

Radiance measurements and inversions of the AErosol RObotic NETwork (AERONET)1 are used to characterize global atmospheric aerosols and key parameters such as the phase functions and column extinction-to-backscatter ratio (lidar ratio, Sa) for the analysis of lidar measurements. This study uses more than 105 records of aerosol size distributions and complex refractive indices to generate several optical properties of the aerosol at more 200 sites worldwide. These properties together with the radiance measurements are then classified using classical clustering methods which group the sites according to the type of aerosol with the greatest frequency of occurrence at that site. Six significant clusters are identified: two types of desert dust, biomass burning, polluted continental, clean continental, and a dust+smoke aerosol. In addition to categorizing the aerosol types, all the column properties that are important for the analysis and validation of lidar measurements such as the lidar ratio, optical depth and phase functions are determined for each of the seven aerosol types. The variances of the aerosol determined using principle component analysis (PCA). Aerosol lidar ratios at 532 nm of the six categories of aerosol are calculated.