A permanent raman lidar station in the Amazon: description, characterization and first results

Abstract

Abstract. A permanent UV Raman Lidar station, designed to perform continuous measurements of aerosols and water vapor and aiming to study and monitor the atmosphere on the weather to climatic time scales, became operational in central Amazon in July 2011. The automated data acquisition and internet monitoring enabled extended hours of daily measurements when compared to a manually operated instrument. This paper gives a technical description of the system, presents its experimental characterization and the algorithms used for obtaining the aerosol optical properties and identifying the cloud layers. Data from one week of measurements during the dry season of 2011 were analyzed as a mean to assess the overall system capability and performance. A comparison of the aerosol optical depth from the Lidar and a co-located AERONET sun photometer showed a root mean square error of about 0.06, small compared to the range of observed AOD values (0.1 to 0.75) and to the typical AERONET AOD uncertainty (0.02). By combining nighttime measurements of the aerosol lidar ratio (50–65 sr), backtrajectories calculations and fire spots observed from satellites we showed that observed particles originated from biomass burning. Cirrus clouds were observed in 60% of our measurements. Most of the time they were distributed into three layers between 11.5 and 13.4 km a.g.l. The systematic and long-term measurements being made by this new scientific facility have the potential to significantly improve our understanding of the climatic implications of the anthropogenic changes in aerosol concentrations over the pristine Amazônia.