BALLOON-BORNE MEASUREMENTS OF CLO, NO, AND O3 IN A VOLCANIC CLOUD - AN ANALYSIS OF HETEROGENEOUS CHEMISTRY BETWEEN 20 AND 30 KM

Balloon profiles of chlorine monoxide (ClO), nitric oxide (NO), and oz one (O3) were measured on March 11, 1992 from 100 to 10 mb over Greenl and (67.0-degrees-N, 50.6-degrees-W). Measurements from SAGE II indica te that the aerosol surface area in the region was enhanced by sulfur from the eruption of Mt. Pinatubo, reaching 50 times background near 2 0 km. Concentrations of CIO were enhanced and concentrations of NO wer e suppressed relative to low aerosol conditions consistent with the ef fects of hydrolysis of N2O5 on the surface of sulfuric acid aerosols. The data are consistent with a value of 2x10(-4) for the reaction prob ability of the heterogeneous hydrolysis of ClONO2, indicating a minor role for this reaction at a temperature of 220 K. At these temperature s, we find no evidence for the catastrophic loss of ozone predicted to occur under conditions of enhanced aerosol surface area.