Estimation of Aerosol Effective Radius by Multiwavelength Elastic Lidar

A new lidar algorithm is presented as part of a technique for estimating aerosol concentration and particle-size distribution (PSD). This technique uses a form of the extended Kalman filter (EKF), wherein the target aerosol is represented as a linear combination of basis-aerosols, so that the estimated PSD of the aerosol is a linear combination of the PSD of the individual basis-aerosols. The state vector of the filter contains the amplitudes of the basis-aerosols, eliminating the need for an intermediate step of estimating scattering coefficients. Point-sensor instruments and Mie scattering theory are used to establish the relationship between basis-aerosols and measured power. The algorithm is demonstrated using both synthetic test data and field measurements of biological and nonbiological aerosols. The estimated PSD allows straightforward calculation of parameters such as volume-fraction concentration and effective radius.