Measurements of Gas Phase Stratospheric Sulfur

Abstract:

Carbonyl sulfide (COS) and sulfur dioxide (SO₂) are, besides the direct injection of aerosols, the two major species determining the aerosol content of the stratosphere. In this talk, we will try to provide an overview of stratospheric measurements of both trace gases since the beginning of the millennium. Observations in these last 15 years opened the possibility to study the stratospheric content, the vertically resolved distributions and the temporal evolution of the aerosol precursor gases due to the availability of space-borne limb-sounding instruments, like the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), the Atmospheric Chemistry Experiment – Fourier Transform Spectrometer (ACE-FTS) and the Microwave Limb Sounder (MLS). While this kind of measurements are and will be more rarely or even not existent any more in the future, the growing number of nadir looking instruments provide horizontally high resolved views of SO₂ after volcanic eruptions. Further, ground-based FTS and in-situ observations reaching the lower stratosphere contribute to our knowledge on SO₂ and OCS. We will discuss results from these different instruments with respect to their specific observational constraints and we will try to gain further inside into measurement uncertainties by showing intercomparisons between those datasets and derived products. As an example, vertically resolved lifetimes of SO₂ derived from MIPAS observations after volcanic eruptions allow to evaluate the results derived from satellite based nadir measurements in the infrared and UV/Vis spectral range.