Sulfur dioxide sources in the stratosphere

Abstract

Version 5.2 SO2 data from the Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) in low Earth orbit are used to determine global altitude-latitude abundance distributions. This new data set has SO2 volume mixing ratios (VMRs) from 11.5 to 39.5 km in altitude from February 2004 to July 2023. The average background SO2 abundance is plotted along with the abundance for four different seasons. These distributions show that there is a stratospheric source of SO2 that comes from the decline in sulfate aerosol abundance with increasing altitude. The visible and near-infrared photolysis of sulfuric acid (H2SO4) is the primary source of SO2 in the middle stratosphere. There is also a source of SO2 in the upper stratosphere and mesosphere. The Brewer-Dobson circulation enhances SO2 at higher altitudes, particularly by descent near the winter pole. The elevated abundance of SO2 near the poles originates from meteoric sources as well as UV photolysis of H2SO4 in the mesosphere. Large volcanic eruptions release sulfur dioxide (SO2) into the lower stratosphere, where it persists for several months.