Measurement of tropospheric aerosol in São Paulo area using a new upgraded Raman LIDAR system

ABSTRACT Elastic backscatter LIDAR systems have been used to determine aerosol pro le concentration in several areas suchas weather, pollution and air quality monitoring. In order to determine the aerosol extinction and backscatteringpro les, the Klett inversion method is largely used, but this method su ers from lack of information since thereare two unknown variables to be determined using only one measured LIDAR signal, and assumption of theLIDAR ratio (the relation between the extinction and backscattering coecients) is needed.When a RamanLIDAR system is used, the inelastic backscattering signal is a ected by aerosol extinction but not by aerosolbackscatter, which allows this LIDAR to uniquely determine extinction and backscattering coecients withoutany assumptions or any collocated instruments. The MSP-LIDAR system, set-up in a highly dense suburbanarea in the city of S~ao Paulo, has been upgraded to a Raman LIDAR, and in its actual 6-channel con gurationallows it to monitor elastic backscatter at 355 and 532 nm together with nitrogen and water vapor Ramanbackscatters at 387nm and 608 nm and 408nm and 660 nm, respectively. Thus, the measurements of aerosolbackscattering, extinction coecients and water vapor mixing ratio in the Planetary Boundary Layer (PBL) arebecoming available. The system will provide the important meteorological parameters such as Aerosol OpticalDepth (AOD) and will be used for the study of aerosol variations in lower troposphere over the city of S~aoPaulo, air quality monitoring and for estimation of humidity impact on the aerosol optical properties, withoutany a priori assumption. This study will present the rst results obtained with this upgraded LIDAR system,demonstrating the high quality of obtained aerosol and water vapor data. For that purpose, we compared thedata obtained with the new MSP-Raman LIDAR with a mobile Raman LIDAR collocated at the Center forLasers and Applications, Nuclear and Energy Research Institute in S~ao Paulo and radiosonde data from Campode Marte Airport, in S~ao Paulo.Keywords: LIDAR, Aerosols, Optical Properties, Water Vapor