Análise das propriedades ópticas dos aerossóis na atmosfera sobre Natal/RN a partir de dados dos sistemas Calipso e Duster

Abstract

This work aims to analyze atmospheric aerosols over Natal/RN by means of its optical properties. Ten years (2007-2016) of data were obtained from the CALIPSO satellite, which has an on-board Lidar called CALIOP. CALIPSO data obtained at most within a radius of 120 km around Natal were used to obtain the optical Aerosol Depth (AOD), the lidar ratio (RL) and the altitude of the base and top of the aerossol layers. A case study was carried out for the month of September using the aerosol subtype masks generated by CALIPSO. Air mass trajectories with the HYSPLIT model were also used to identify the region of origin of the measured aerosols. The objective of choosing data about the region was to carry out a data comparison study of the terrestrial DUSTER/Lidar at UFRN in Natal, with data from coincident days of CALIPSO passages. Vertical profiles of the return signal were generated at 532 nm, and backscatter profiles attenuated at 532 nm of CALIPSO. The analysis of the aerosol optical depth (AOD) showed that their monthly mean variability did not exceed values greater than 0,16. The months that presented lower concentrations had an average AOD of 0,04. The AOD frequency histograms showed that the types of clean continental, marine and dusty aerosols have little variable values. The aerossol types that presented the greatest variation were the type of continental/smoke pollution. According to the RL analysis, Natal presented values that characterize dusty, burnt, polluted continental and mainly clean marine aerosols. The aerosol layers top and base are at their lowest altitudes during May, June and July, these being the months in which the rainy season occurs, and also during November. The minimum values are always below 1 km of altitude, the months of February and September obtained 25% of the altitudes above 2,5 km, with altitudes of up to 4,9 km. The RL values of 70 sr and the highest values of maximum and minimum height of the aerosol layers, highlighted for the month of September, suggest the hypothesis of cases of biomass burning aerosol detection at high altitudes above the boundary layer, motivating a case study, which showed, on 09/07/2009, 09/13/2011, 09/07/2013 and 09/15/2016, smoke aerosols located at an altitude of 3 to 4 km. With trajectories modeled by HYSPLIT, for 7 days, it can be concluded that these air masses are coming from central Africa, over the Natal atmosphere. Comparison of the DUSTER/Lidar data with the CALIPSO data of 12/06/2016 showed aerossol layers between 1 and 3 km, coinciding in both measurements. The CALIPSO backscatter profile also allowed to observe a layer of dust aerosols at the unusual height of 15 km, suggesting further future studies for interpretation.