Global Observations of Ammonium Balance and pH Indicate More Liquid Aerosol and Acidic Conditions than Current Models Predict. BENJAMIN A. NAULT, Pedro Campuzano-Jost, Douglas Day, Jason Schroder, Roya Bahreini, Huisheng Bian, Mian Chin, Simon Clegg, Peter Colarco, John Crounse, Jack Dibb, Michelle Kim, Jack Kodros, Felipe Lopez-Hilfiker, Eloise Marais, Ann M. Middlebrook, J. Andrew Neuman, John Nowak, Jeffrey R. Pierce, Eric Scheuer, Joel A. Thornton, Kostas Tsigaridis, Patrick Veres, Paul Wennberg, Jose-Luis Jimenez, CIRES, University of Colorado, Boulder