Ani Sobral Torres¹, Eduardo Landulfo¹, Walter Morinobu Nakaema¹, Fabio Juliano da Silva Lopes¹

¹Instituto de Pesquisas Energeticas e Nucleares/Universidade de Sao Paulo

A backscattering LIDAR (Light Detection and Ranging) system,  has been set-up in a suburban area in the city of São Paulo (23° 33’ S, 46°44’ W) to provide the vertical profile of the aerosol backscatter coefficient at 532 nm up to an altitude of 4-6 km above sea level (asl). This Lidar system was developed in the Laboratory of Environmental Laser Applications at the Center of Laser and Applications (CLA) at the Instituto de Pesquisas Energéticas e Nucleares – IPEN and is operational since September 2001. The LIDAR data products which can be provided are aerosol optical thickness (AOT) in the visible, aerosol backscattering and extinction coefficients at 532 nm, clouds and the Planetary Boundary Layer (PBL) heights, aerosol layering and the structure of the lower troposphere over the city of São Paulo. The Lidar measurements are complemented with aerosol optical thickness measurements obtained by a CIMEL sun-tracking photometer (which belongs to the AERONET network) in the visible spectral region, not only to validate the lidar data, but also to provide an input value of the so-called extinction-to-backscatter ratio (Lidar Ratio – LR).

A correlation between Lidar data and the data obtained by a CIMEL sun-tracking photometer placed in Sao Paulo is also being made to set a temporal database of those data which were collected concomitantly and to cross the information obtained by each instrument to the year of 2005. One important trend noticed is a seasonal signature in the LR indicating a change of the predominant type of aerosol between the dry and wet seasons during the year of 2005.