Caracterização e classificação das propriedades ópticas de aerossóis na atmosfera de Natal, Brasil

Abstract

In this study the first characterization and classification of atmospheric aerosols over Natal (RN) based on the presented optical properties is envisioned. A Cimel solar photometer was used for obtaining the Aerosol Optical Depth (AOD) and Ångström coefficient (α) in the period from January 29th to July 5th 2016. The Natal data base belongs to the RIMA and AERONET networks, and is part of a collaboration partnership between the Nuclear and Energy Research Institute (IPEN), the University of Granada (UGR) and the Research Group for Modeling and Monitoring of Atmospheric Chemistry (GP-MOQA / Department of Atmospheric and Climate Sciences / CCET / UFRN). During the measurement period, 31% of the measurements days were valid data, from these days the mean value of AOD (500 nm) was 0.112 (± 0.074), indicating marine aerosols. Additionally, the mean value of α (500-870 nm) was 0.140 (± 0.203), the expected values for coastal zones are less than 1. From frequency analysis of histograms the characteristics of marine aerosols were confirmed as most values AOD were smaller than 0.15 and α values were below 0.4. The local aerosol classification is confirmed by a scatter plot of AOD versus α where 62% of aerosols present in the atmospheric column Natal (RN) were marine aerosols, 19% were disregarded because of negative values and 19% of the aerosols were not classified in this study. The classification and characterization of aerosols were confirmed by modeling backward trajectories of the HYSPLIT model, the majority (93% at 500 m, 69% at 1500 m and 28% at 3000 m height) of air masses frequency were originated in the Southeast Atlantic Ocean. During the study period and under the methodology used the presence of desert aerosols were not confirmed, neither the presence of air masses coming from the African Continent.