The vertical distribution of volcanic SO₂ plumes measured by IASI

Abstract. Sulfur dioxide (SO₂) is an important atmospheric constituent that plays a crucial role in many atmospheric processes. Volcanic eruptions are a significant source of atmospheric SO₂ and its effects and lifetime depend on the SO₂ injection altitude. The Infrared Atmospheric Sounding Interferometer (IASI) on the METOP satellite can be used to study volcanic emission of SO₂ using high-spectral resolution measurements from 1000 to 1200 and from 1300 to 1410 cm⁻¹ (the 7.3 and 8.7 µm SO₂ bands) returning both SO₂ amount and altitude data. The scheme described in Carboni et al. (2012) has been applied to measure volcanic SO₂ amount and altitude for 14 explosive eruptions from 2008 to 2012. The work includes a comparison with the following independent measurements: (i) the SO₂ column amounts from the 2010 Eyjafjallajökull plumes have been compared with Brewer ground measurements over Europe; (ii) the SO₂ plumes heights, for the 2010 Eyjafjallajökull and 2011 Grimsvötn eruptions, have been compared with CALIPSO backscatter profiles. The results of the comparisons show that IASI SO₂ measurements are not affected by underlying cloud and are consistent (within the retrieved errors) with the other measurements. The series of analysed eruptions (2008 to 2012) show that the biggest emitter of volcanic SO₂ was Nabro, followed by Kasatochi and Grímsvötn. Our observations also show a tendency for volcanic SO₂ to reach the level of the tropopause during many of the moderately explosive eruptions observed. For the eruptions observed, this tendency was independent of the maximum amount of SO₂ (e.g. 0.2 Tg for Dalafilla compared with 1.6 Tg for Nabro) and of the volcanic explosive index (between 3 and 5).