Temperature and ozone anomalies as indicators of volcanic soot in the stratosphere

Abstract

The role of volcanogenic aerosols in the formation of ozone and temperature anomalies in the tropical stratosphere recorded after the eruption of Mount Pinatubo in June, 1991, is analyzed in the work on the basis of 30-year balloon measurement data series at the Hilo station (Hawaii). Positive temperature and negative ozone deviations in vertical profiles ≥2σ from normal annual are considered as anomalies. The stratospheric anomalies observed in the second half of 1991 agree well with the presence of volcanic ash remaining in the stratosphere for about six months. However, temperature anomalies and stratospheric ozone depression, observed during next 2–3 years, cannot be explained by long-lived sulfuric acid aerosol. A mechanism is suggested for the formation of long-lived volcanic soot particles in the stratosphere due to thermal decomposition of methane in the eruption column, which actively absorb solar radiation and destroy ozone on their surfaces. The largest ozone anomaly observed in the lower stratosphere in the second half of 1992 is explained by the soot deposition rate calculated accounting for the high efficiency of ozone destruction on its surface.