LIDAR LiO3T - La Réunion Maïdo station - Level 2B Aerosol

The Tropospheric Ozone Lidar (LiO3T) works with the DIfferential Absorption Lidar (DIAL) technique and provides vertical profiles of ozone (O3) concentration in the troposphere, between 6 and 25 km. To this end, two different wavelengths are emitted using stimulated Raman scattering: a 289 nm signal strongly absorbed by ozone molecules and a 316 nm signal weakly absorbed by ozone molecules. Vertical profiles of aerosol light extinction and backscattering can be retrieved from the residual emission of the laser in terms of elastic scattering at 532 nm and 1064 nm, and Raman N2 scattering at 607 nm. From 1993 to 2012, the LiO3T was located at the Moufia University campsite in Saint-Denis and provided ozone vertical profiles. It was moved to the Maïdo facility in 2012 and has been measuring from this location since 2013. The first aerosol dedicated polarized channels at 532nm were installed in 2014.

The Observatory of Atmospheric Physics of La Réunion (OPAR), located on Réunion Island near Madagascar (21.079°S, 55.383°E), is currently equipped with more than 50 instruments distributed over three different sites: two historical coastal sites in the north, and a high-altitude site (Maïdo observatory, 2160 m asl), which now houses more than two-thirds of these instruments. OPAR is part of many international networks, including GAW (Global Atmospheric Watch), NDACC (Network for the Detection of Atmospheric Composition Change), SHADOZ (Southern Hemisphere Additional OZonesondes), and AERONET (Aerosol Robotic Network). Additionally, it is a part of the European research infrastructures ACTRIS (Aerosol, Clouds, and Trace Gases Research Infrastructure) and ICOS (Integrated Carbon Observing System).

The data is processed in two stages: initially, the data are manually cleaned of disturbed profiles, either by atmospheric effects, such as the passage of clouds, or by electronic effects like noise. They are then summed over the night. This is the L1b level. Subsequently, the data are processed to convert from a profile of received photon number to a profile of aerosol extinction and scattering. The methodology used is based on the Klett calculation at one wavelength. This is the L2b level, and the data are available in the NetCDF format (.nc) with the NDACC convention in the choice of variable names.

Time series of the LiO3T level 2B aerosol profile product correspond to the second stage of the process. The final file is in NetCDF format, with the NDACC methodology.