SATELLITE CHARACTERIZATION OF POWER PLANT AEROSOL EMISSIONS

Abstract

Aerosol optical thickness is a major atmospheric quantity tuning the Earth radiation budget therefore it has to be determined on a global scale, both over land and ocean. Since the sources of most aerosols (mainly of anthropogenic origin) are located over land, the satellite remote sensing of aerosols over land is particularly important to quantify and characterize these particles in the atmosphere. The aim of the present work is the identification and characterization of aerosols plumes emitted from the Portuguese Electrical Company (EDP) Power Plants using satellite measurements, with the purpose of monitoring the emissions of pollutants and of studying their atmospheric dispersion. The methodology is based on calculations of radiative transfer in the atmosphere that, properly combined with satellite measurements, allow for the detection and determination of the actual amount of aerosols in the atmosphere and some of their physical characteristics. The columnar amount of pollutants obtained in this way (aerosol optical thickness) is compared with the emissions of particles that are monitored on the top of the power plant towers, in order to validate the values retrieved from the satellite-based method. Satellite measurements from the MODerate Resolution Imaging Spectroradiometer (MODIS) were used in the study, since they present the adequate spectral channels and spatial resolution (250 x 250 m2 in some spectral channels) to observe and monitor disturbances in the Earth-atmosphere system. At the same time, information about the wind direction and intensity at the power plant towers altitude, and the aerosol backtrajectories analysis of 24 hours, at the same height, were used in order to guarantee that there is no contamination from other aerosol sources apart from the one under study. The analysis of the aerosol optical thickness values obtained with the satellite based methodology, confirmed that a higher value of optical thickness exists in the areas where the Power Plants are located and, in some of them, a good agreement can be observed (high positive correlation) between the values of the optical thickness obtained from the satellite data and the aerosol emissions measured at the top of the power plant towers.