H₂SO₄ photolysis: A source of sulfur dioxide in the upper stratosphere

Abstract

Numerous absorption lines of stratospheric sulfur dioxide (SO2) have been identified in solar occultation spectra recorded by the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier transform spectrometer during the Atmospheric Laboratory for Applications and Science (ATLAS)‐1 shuttle mission (March 24‐April 2, 1992). Based on their analysis, a volume mixing ratio profile of SO2 increasing from (13 ± 4) p.p.t.v. (parts per 10−12 by volume) at 16 mbar (∼ 28 km) to 455 ± 90 p.p.t.v. at 0.63 mbar (∼ 52 km) has been measured with no significant profile differences between 20°N and 60°S latitude. The increase in the SO2 mixing ratios with altitude indicates the presence of a source of SO2 in the upper stratosphere. Profiles retrieved from ATMOS spectra recorded during shuttle flights in April‐May 1985 and April 1993 show similar vertical distributions but lower concentrations. Two‐dimensional model calculations with SO2 assumed as the end product of H2SO4 photolysis produce SO2 profiles consistent with the ATMOS measurements to within about a factor of 2.

Quasi-biennial oscillation of the tropical stratospheric aerosol layer

“…But those are predominately confined to the lowermost regions of the mid-and high latitudes, so that they cannot be taken into consideration within this study that focus on the tropical LS. Above 30 km, data from only one campaign were available until last year (2013) -which measured SO 2 in the NH subtropics (ATMOS infrared spectrometer on a NASA Space Shuttle in 1985; Rinsland et al, 1995). Recently a climatology of monthly and zonal mean profiles of SO 2 volume mixing ratios has been derived from Envisat/MIPAS measurements in the altitude range 15-45 km for the period from July 2002 to April 2012 (Höpfner et al, 2013).…”

“…Only a few individual measurements of the two gases were conducted in the stratosphere during balloon ascents in the 1970s and 1980s (see Hommel et al, 2011, herein referred to as HOM11, for a review). Only a single remotely sensed SO 2 profile existed for altitudes above 30 km, obtained during a NASA Space Shuttle mission in 1986 (Rinsland et al, 1995) until very recently -a new SO 2 data set has now been derived from Envisat/MIPAS observations (Höpfner et al, 2013).…”

HSO3Cl: a prototype molecule for studying OH-stretching overtone induced photodissociation

“…13 Additionally, the formation of a layer of dispersed aerosol found at high altitudes (between 15 to 35 km) which influences stratospheric ozone depletion, the so called Junge layer 14 , can be explained by the cycling between SO 2 and H 2 SO 4 . [15][16][17] Sulfur-containing compounds, in particular the interplay between H 2 SO 4 and SO 2 , are important in the formation of atmospheric aerosols. The observed anomalous enhancement in particle concentration during springtime and the finding that SO 2 concentration from high altitude photolysis of H 2 SO 4 is constant or increases with altitude 16 suggested that at high altitudes photolysis of sulfuric acid is the source of SO 2 .…”

“…[15][16][17] Sulfur-containing compounds, in particular the interplay between H 2 SO 4 and SO 2 , are important in the formation of atmospheric aerosols. The observed anomalous enhancement in particle concentration during springtime and the finding that SO 2 concentration from high altitude photolysis of H 2 SO 4 is constant or increases with altitude 16 suggested that at high altitudes photolysis of sulfuric acid is the source of SO 2 . 18 However, experimental and computational investigations were unable to find the electronic absorption spectrum of H 2 SO 4 down to 140 nm.…”

Calculated two-photon electronic transitions in sulfuric acid and its atmospheric relevance

“…The photodissociation process of H 2 SO 4 was initially thought to occur via electronic excitation in the UV region [6,7]. However, both experiments and ab initio calculations have repudiated this [8][9][10][11][12].…”