Estimation in situ of extinction coefficient of particles using Cavity Ring-Down Spectrometer

Abstract

Lidar measurements present limitation regarding to the determination of extinction coefficient on the surface (where most aerosol particles are concentrated) due to geometrical issues and overlap functions. An attempt to overcome these feature, it is purposed an approach using a Cavity Ring-Down Spectrometer (CRDS) for monitoring in situ the optical properties of aerosols in a continuous visible-range between 630 and 650 nm. The CRDS is a very sensitive and calibration-free direct absorption spectroscopic technique that provides absolute values of optical extinction by samples that scatter and absorb light. Simultaneous measurements of scattering and extinction coefficients were performed by an elastic lidar in order to compare the respective magnitude of values.