Measurements of OH, H₂SO₄, and MSA at the South Pole during ISCAT

The first measurements of OH, H 2 SO 4 , and MSA performed at the South Pole as part of the Investigation of Sulfur Chemistry in the Antarctic Troposphere (ISCAT) study are presented. OH concentrations were found to be quite elevated for such a dry environment, with average values of 2x10 6 molecule cm −3 . Model simulations suggest that much of the observed OH is a result of unexpectedly high NO concentrations. Concentrations of H 2 SO 4 and MSA were generally low with average values of 2.5x10 5 and 1x10 5 molecule cm −3 , respectively. Major variations in the concentration levels of the above species were found to have a high correlation with changes in the polar mixing layer as estimated from the measured temperature difference from 22 to 2m above the snow surface. Chemical details are discussed.