Raman Lidar monitors emissions from sugar cane fires in the State of São Paulo: a pilot-project integrating radar, sodar, aerosol and gas observations

Abstract

Ourinhos is situated in one of the major sugar cane producing regions in the State of São Paulo, where the manual harvesting is generally preceded by burning the foliage, resulting in large quantities of aerosols being emitted into the atmosphere. A onemonth pilot study was executed during August 2010, to characterize the effects of those emissions on the atmosphere, considering the local circulation and the consequences for the region. The plumes were tracked by IPMet´s two S-band Doppler radars, also deploying a large range of meteorological, physical and chemistry instrumentation: a mobile Lidar with Raman channel to observe elevated layers and the type of aerosols, a medium-sized Sodar, as well as 6 Automatic Weather Stations spread through town. Various gases and particulates were also sampled, providing the atmospheric chemistry data base and thus documenting the impact on the region. This paper highlights a case study on 26 August, when a plume was tracked by TITAN Radar Software from the start of the fire, moving southwards at 14-17 km.h-1 with the winds at about 3,5 km above ground level, until it reached Ourinhos 2h15min later, where it was observed by the Raman Lidar and also detected by the aerosol and gas samplers. The high aerosol load of the atmosphere was confirmed by hourly mean values of AOD varying between 0,265 and 0,288 until 07:00 LT, after which they increased to 0,433 by 09:00 LT, as well as hourly mean backscatter profiles. Hourly values of the Lidar Ratio identified the aerosols as biomass burning products, also confirmed through the analysis of gas and aerosol samples simultaneously collected at the Lidar site.