Sulfur dioxide sources in the stratosphere

Abstract

Version 5.2 SO${}_2$ 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 SO${}_2$ volume mixing ratios (VMRs) from 11.5 to 39.5 km in altitude from February 2004 to July 2023. The average background SO${}_2$ abundance is plotted along with the abundance for four different seasons. These distributions show that there is a stratospheric source of SO${}_2$ that comes from the decline in sulfate aerosol abundance with increasing altitude. The visible and near-infrared photolysis of sulfuric acid (H${}_2$SO${}_4$) is the primary source of SO${}_2$ in the middle stratosphere. There is also a source of SO${}_2$ in the upper stratosphere and mesosphere. The Brewer-Dobson circulation enhances SO${}_2$ at higher altitudes, particularly by descent near the winter pole. The elevated abundance of SO${}_2$ near the poles originates from meteoric sources as well as UV photolysis of H${}_2$SO${}_4$ in the mesosphere. Large volcanic eruptions release sulfur dioxide (SO${}_2$) into the lower stratosphere, where it persists for several months.