Abstract View
Models Underestimate the Increase of Acidity with Remoteness Biasing Radiative Impact Calculations
BENJAMIN A. NAULT, Pedro Campuzano-Jost, Douglas Day, Duseong Jo, Roya Bahreini, Huisheng Bian, Simon Clegg, Jack Dibb, Alma Hodzic, Alma Hodzic, Joseph Katich, Agnieszka Kupc, Eloise Marais, J. Andrew Neuman, John Nowak, Brett Palm, Fabien Paulot, Jeffrey R. Pierce, Gregory Schill, Joel A. Thornton, Kostas Tsigaridis, Paul Wennberg, Christina Williamson, Jose-Luis Jimenez, et al., CIRES, University of Colorado, Boulder
Abstract Number: 565
Working Group: Aerosol Chemistry
Abstract
The inorganic fraction of fine atmospheric aerosol affects numerous physical and chemical processes. However, due to limited global measurements, there is large uncertainty in its burden, composition, and lifetime. Here, extensive airborne observations are used to investigate how two measures of aerosol acidity, the fraction of anions neutralized by ammonium (ammonium balance), and aerosol pH, change from polluted to remote regions. Both parameters strongly decrease with remoteness (distance from source) at all altitudes. Chemical transport models tend to show more neutralized aerosols and higher pH than observed. We show that part of the discrepancy is due to a frequent high bias in ammonia emissions or lifetime, and/or the incorrect assumption of internally mixed sea-salt. The observations suggest very different aerosol properties and impacts, including higher water content and a smaller direct radiative effect. These results indicate the need for better constraints on the emissions and lifetime of inorganic aerosol precursors, especially ammonia.