1. Monitoring volcanic haze from space: the Bárðarbunga fissure eruption OMI Science Team Meeting 31 August – 2 September 2015, KNMI, de Bilt Image: VIIRS volcanic ash & SO2 RGB, 23 September 2014, 12:20 UTC

2. Monitoring volcanic haze from space: the Bárðarbunga fissure eruption [Bárðarbunga aka Holuhraun !!!] Jos de Laat (KNMI) Sophie Smits (TU Delft, M.Sc) Martin de Graaf (TU Delft/ KNMI)

3. Bárðarbunga eruption Aug 2014 - March 2015

4. Factsheet Bárðarbunga - Late August 2014 to early March 2015 - Fissure eruption, fairly constant lava flow rate - 1.6 ± 0.3 km 3 of lava produced, 5-11 Mt SO 2 [Gíslason et al., 2015] - Strength 5-10% of Laki 1783 (= ~ 100 Mt SO 2, ~ 15 km 3 of lava) [Stevenson et al., 2003; Gíslason et al., 2015] - Air quality standards on Iceland frequently exceeded - Occasional transport towards western Europe - Few problems with air quality in western Europe and Scandinavia

5. What made Bárðarbunga special? - many recent eruptions with lots of SO 2 2006 Soufrière Hills (Montserrat, Caribic) 2008 Kasatochi (Alaska, Aleutian Islands) ------------  2009 Sarychev (Kamtjatska, Kuril Islands) 2010 Eyjafjallajokull (Iceland) 2010 Merapi (Indonesia) 2011 Grimsvotn (Iceland) 2011 Nabro (Ethiopia) 2011 PuyeHue Cordon-Caulle (Chile) - all explosive eruptions, free tropospheric SO 2 - Bardarbunga: to our knowledge the first time satellite history eruption of this combined type, strength and duration. This type = fairly constant surface emissions, long duration of eruption

6. Bárðarbunga impact - formation of volcanic haze (“vog”) - SO 2 transformed into sulfuric acid (H 2 SO 4 ) - damaging to plants, affects the respiratory system in animals and humans. - Laki 1783: thousands of deaths on Iceland, failed crops - many more casualties throughout Europe, either directly or due to crop failure, famines or climatic effects (coldness)

7. Bárðarbunga: observing VOG formation [1] Research Questions: - Can we observe particle formation from SO 2 with satellites? - Is there a relation between SO 2 and aerosols? - What are the complexities of satellite observations of SO 2 and aerosols? clouds, strong winds & fast transport, time difference MODIS & OMI observations - Is there added value in monitoring aerosols for such an eruption?

8. 24 September 2014 1 October 2014 Bárðarbunga eruption, SO 2 and aerosol formation Large image: MODIS AOT (NASA), insert: OMI SO2 (TEMIS KNMI/BIRA)

9. Bárðarbunga: observing VOG formation [2] Method: - Analyze OMI SO 2 and MODIS AOT - similar spatial resolution (OMI 13×24 km 2 vs MODIS 10×10 km 2 ) - good coverage of Iceland region (multiple scenes per day from OMI) - OMI OMSO2 boundary layer SO 2 product - MODIS AOT and MODIS AOT Fine Mode Fraction (FMF) (OCEAN ONLY !!!) - all days in September and October (not later due to Polar winter)

10. Example: 5 September 2014 - enhanced AOT - high value MODIS FMF (Small Ratio) - aerosols from SO 2 are expected to be small Complications: OMI row anomaly enhanced non-SO 2 AOT elsewhere clouds

11. Analysis - 61 days to check - 14 days (26 cases) of either AOT or SO 2 - 12 cases with low AOT, little SO 2 - 7 cases with high AOT, little SO 2 - 3 cases with low AOT, high SO 2 - 4 cases with high AOT, high SO 2 Explanations: - time difference & plume displacement - other aerosols sources Much AOTOLRR2R2 SO 2 maxAOTmaxN Much SO 2 05-09-2014 V 08-09-2014 09-09-2014 20-09-2014 I 2.3 ± 0.2 6.3 ± 0.9 4.8 ± 2.4 4.5 ± 0.6 0.42 0.49 0.10 0.46 40 28 25 33 121 78 98 122 0.18 0.30 0.46 0.29 0.52 0.82 0.79 0.80 178 24 21 59 Little AOTOLRR2R2 SO 2 maxAOTmaxN Much SO 2 02-09-2014 II 05-09-2014 IV 20-09-2014 II -1.1 ± 0.9 1.0 ± 0.7 0.1 ± 1.6 0.02 0.09 0.00 24 48 24 51 108 52 0.11 0.21 0.09 0.41 0.44 0.15 48 28 17 Little AOT OLRR2R2 SO 2 maxAOTmaxN Little SO 2 02-09-2014 I 05-09-2014 I 05-09-2014 III 14-09-2014 I 14-09-2014 II 21-09-2014 I 24-09-2014 01-10-2014 03-10-2014 07-10-2014 08-10-2014 I 08-10-2014 II 3.2 ± 2.3 2.3 ± 3.6 6.2 ± 4.3 4.0 ± 0.8 3.8 ± 1.0 6.9 ± 2.7 5.1 ± 0.4 3.6 ± 2.7 3.2 ± 1.2 4.8 ± 2.3 3.2 ± 1.9 6.6 ± 1.2 0.16 0.00 0.06 0.10 0.06 0.04 0.52 0.19 0.04 0.03 0.06 0.22 12 8 9 14 12 8 16 15 8 7 9 36 14 15 37 35 16 33 34 26 11 26 23 0.24 0.16 0.10 0.15 0.16 0.21 0.15 0.20 0.17 0.14 0.19 0.38 0.25 0.46 0.51 0.47 0.55 0.44 0.41 0.28 0.33 0.24 0.32 17 29 25 173 138 58 134 32 51 27 29 115 Much AOTOLRR2R2 SO 2 maxAOTmaxN Little SO 2 04-09-2014 II 04-09-2014 III 05-09-2014 VII 06-09-2014 12-09-2014 I 12-09-2014 II 10-10-2014 4.3 ± 7.2 9.7 ± 1.6 2.3 ± 0.8 7.1 ± 1.2 4.8 ± 0.7 6.3 ± 0.7 2.8 ± 0.9 0.03 0.64 0.20 0.21 0.30 0.52 0.09 19 25 16 21 16 35 45 56 38 45 38 36 0.37 0.41 0.18 0.28 0.22 0.27 0.18 0.71 0.60 0.44 0.70 0.37 0.47 0.51 18 42 56 60 37 68 132

12. Plume displacement thingy … 2 September 2014 case: -no correlation SO 2 & AOT -time difference 41 min -fresh plume -small change wind direction Colors indicate distance from volcano (blueish 500 km) Estimated OMI SO2 uncertainty 5 DU

13. Cases: the good, the bad, the ugly … REMOVE ALL SO 2 MEASUREMENTS < 5 DU

14. The golden case (5 Sep 2014) … -good correlation (R 2 = 0.46) -R 2 = 0.61 for distances up to 650 km (blueish) -R 2 = 0.68 for distances beyond 650 km (redish) -Plume aging, dispersion: SO 2, AOD ???

15. Summary - compared OMI SO 2 and MODIS AOT for Bárðarbunga eruption Sep-Oct 2014 - reduced number of useful cases due to clouds, OMI row anomaly - even fewer useful cases due to plume displacement (obs. times differ) Conclusions - clear evidence of enhanced AOT due to conversion SO 2 into particles - one golden case: good correlation between AOT and SO 2 - some evidence for plume aging effects (lifetimes, dispersion, chemistry ??) - there is added value in monitoring AOT for such eruptions (despite complications of collocating SO 2 and AOT measurements)  cloudy region, any information is welcome … paper in preparation: de Laat et al. 2015

16. That’s all