Seasonal Variability of Intrinsic and Extrinsic Aerosol Optical and Physical Properties from the Eastern North Atlantic (ENA) Aerosol Observing System (AOS) in 2016 and 2017
Poster PDF
Authors
Francesca Gallo — NASA Langley
Allison C Aiken — Los Alamos National Laboratory
Connor J. Flynn — University of Oklahoma School of Meteorology
Stephen R. Springston — Brookhaven National Laboratory
Annette S. Koontz — Pacific Northwest National Laboratory
Jian Wang — Washington University in St. Louis
Eduardo Brito Azevedo — University of the Azores
Kim L. Nitschke — Los Alamos National Laboratory
Category
General topics – Aerosols
Description
The Eastern North Atlantic (ENA) ARM Facility, located on Graciosa Island, in the Azores archipelago, provides continuous measurement of in situ aerosol properties. Throughout the year, the region experiences strong meteorological variability due to the presence of the subtropical Azores High in the summer and midlatitude, tropical and extratropical cyclones during the winter. As a consequence, aerosol composition and concentration vary seasonally. Here, we present preliminary results on the seasonal variation of aerosol scattering and absorption coefficients (Babs and Bsca) for submicron (PM1) and sub-10 µm (PM10) diameter size cuts Aerosol Observing System (AOS) data from 2016 and 2017. Intensive aerosol optical properties such as light scattering and absorption Angstrom exponents (SAE and AAE) are determined with the 3 wavelength Nephelometer (450, 550, 700 nm) and PSAP (464, 529, 648 nm) at ENA. Preliminary results from 2016 indicate a seasonal trend in the PM1 and PM10 aerosol. Total aerosol Bsca is dominated by the supermicron species while Babs is dominated by the submicron. Both PM1 and PM10 Bsca are highest in the winter and lowest in the summer, ranging from seasonal averages of 5.7 – 7.9 Mm-1 and 15.6 – 26.1 Mm-1, respectively. Babs is dominated by the PM1 fraction throughout the year and has less variability (0.63 ± 0.08 Mm-1). However, intensive aerosol absoption properties do indicate a seasonal trend with AAE. AAE is highest in the winter while SAE is highest in the summer indicating the dominance of small particle diameters in the summer and the presence of mixed absorption species in the winter including dust, soot and brown carbon. Changes in both meteorological conditions and emission source through the year could explain these variations. Wind speed (5.36 ± 1.04 m s-1) and direction are also evaluated as is total aerosol number concentration (798 ± 460 particles per cm3).Preliminary analysis indicates a peak in aerosol number concentration in the spring and the largest optical aerosol diversity in winter. Future work will include incorporation of aerosol size distributions from the UHSAS and chemical composition from the ACSM to further investigate the seasonal variability observed in the aerosol optical properties at ENA.
