The effect of the novel HO_2 + NO → HNO_3 reaction channel at South Pole, Antarctica

Abstract

It is well established that the reaction of HO_2 with NO plays a central role in atmospheric chemistry, by way of OH/HO_2 recycling and reduction of ozone depletion by HO_x cycles in the stratosphere and through ozone production in the troposphere. Utilizing a photochemical box model, we investigate the impact of the recently observed HNO_3 production channel (HO_2+NO → HNO_3) on NO_x (NO + NO_2), HO_x (OH + HO_2), HNO_3, and O_3 concentrations in the boundary layer at the South Pole, Antarctica. Our simulations exemplify decreases in peak O_3, NO, NO_2, and OH and an increase in HNO_3. Also, mean OH is in better agreement with observations, while worsening the agreement with O_3, HO_2, and HNO_3 concentrations observed at the South Pole. The reduced concentrations of NO_x are consistent with expected decreases in atmospheric NO_x lifetime as a result of increased sequestration of NO_x into HNO_3. Although we show that the inclusion of the novel HNO_3 production channel brings better agreement of OH with field measurements, the modelled ozone and HNO_3 are worsened, and the changes in NO_x lifetime imply that snowpack NO_x emissions and snowpack nitrate recycling must be re-evaluated.