OBSERVATIONS OF THE LOSS OF STRATOSPHERIC NO2 FOLLOWING VOLCANIC-ERUPTIONS

Observations of stratospheric column amounts of nitrogen dioxide (NO2) , nitric oxide (NO) and nitric acid (HNO3) have been made following ma jor eruptions of the E1 Chichon and Mt. Pinatubo volcanoes. Midlatitud e abundances of NO2 and NO were reduced by as much as 70% in the month s following the appearance of the volcanic aerosols as compared to vol canically quite periods. There are heterogeneous reactions which could occur on the volcanic aerosols to convert NO2 into HNO3 but no commen surate increase in HNO3 column amounts was observed at the times of NO 2 decrease.