Measurement of Pernitric Acid, Nitric Acid and Sulfur Dioxide at the South Pole during ANTCI 2003

Sulfur dioxide, pernitric and nitric acid were measured with a chemical ionization mass spectrometer (CIMS) from the Atmospheric Research Observatory during the ANTCI 2003 austral summer field campaign. Preliminary mean mixing ratios of HNO4 (28 pptv) are comparable to values observed during ISCAT 2000, while the HNO3 mixing ratios (89 pptv) are elevated by a factor of 4. The mean SO2 mixing ratio (10 pptv ) displayed little variation throughout the mission. While the mean values for temperature, dewpoint and ozone between the two field missions are comparable, the NOx mixing ratios were ~2.5 higher during the 2003 ANTCI campaign. The NOx increase is mirrored in the HNO3 mixing ratio but is not as apparent in the HNO4 mixing ratio. Two probable causes for the increase of the HNO3/HNO4 ratio have been identified: 1) Advection of enhanced HNO3 mixing ratios to the South Pole 2) An increase in local production of HNO3 at the South Pole due to elevated NOx concentrations. The relative importance of each will be examined with a simple 0-D photochemical box model.