1. An alert system for volcanic emissions using satellite measurements Nicolas THEYS H. Brenot, J. van Gent and M. Van Roozendael (BIRA-IASB) R. van der A (KNMI) L. Clarisse, P.-F. Coheur, C. Clerbaux (ULB-LATMOS) P. Valks, M. Rix (DLR) 2010 EUMETSAT Meteorological Satellite Conference Córdoba, Spain, 20 – 24 September 2010

2. - Contents - Ash plume from the Eyjafjallajokull eruption on 15 Apr. 2010 © Saeberg/Reuters Support to Aviation Control Service (SACS) Example of results for the eruption of the Eyjafjallajokull volcano System and algorithmic developments

3. Background Volcanic eruptions may bring ash high up into the atmosphere where it poses a threat to aviation. The presence of sulphur dioxide (SO 2 ) is often a tell-tale sign of possible volcanic activity. In the first day or two after an eruption SO 2 and ash will travel together and therefore SO 2 may serve as a marker for the ash.

4. Support to Aviation Control Service (SACS) developed for ESA, within DUE (TEMIS) and GSE (PROMOTE) programmes started in 2006, now extended for 3 years (SACS+) The Support to Aviation Control Service (SACS) intends to deliver in near- real time data from space-based instruments regarding SO 2 and aerosol (ash) data possibly related to volcanic activity. In case of an event notifications are send by email to users, pointing them to a dedicated web page with detailed information. If possible, information on the location, elevation and motion of volcanic plumes will also be provided, in collaboration with the SAVAA project. Notifications of events and data from SACS+ can be useful to the VAACs and other interested users: volcanic observatories, air quality monitoring institutes, scientist, etc. Currently: 66 subscribers Volcanic Ash Advisory Centres (VAACs)

5. Partners in SACS Belgian Institute for Space Aeronomy (BIRA-IASB) leader Royal Netherlands Meteorological Institute (KNMI) Free University of Brussels (ULB) German Aerospace Center (DLR) data provider

6. Data products of SACS InstrumentData typeParticipantsData productsAvailabilityAlerts SCIAMACHY ( ENVISAT) UV/visibleBIRA KNMI SO 2 columns absorbing aerosol index + + GOME-2 (MetOp-A) UV/visibleDLR KNMI SO 2 columns* absorbing aerosol index + [+] OMI ( Aura) UV/visibleKNMISO 2 columns absorbing aerosol index + [+] IASI (MetOp-A) InfraredULBSO 2 index and columns ash indicator [+] Near-real time and archive service + = currently available [+] = to come during SACS+ * Operational product from DLR.

7. SACS portal (hosted by BIRA-IASB) http://sacs.aeronomie.be/

8. Alert system: subscription to e-mail list

9. SO 2 columns 06 May 2010 SCIAMACHY OMI GOME-2 IASI The eruption of the volcano Eyjafjallajokull

10. Aerosols SCIAMACHY OMI GOME-2 IASI The eruption of the volcano Eyjafjallajokull GOME-2 Ash indicator

11. Alert system.. currently only based on SCIAMACHY data Eruption of the Vanuatu Criteria for exceptional SO2 events For each pixel with SO 2 SCD>3 DU, the 8 surrounding pixels are evaluated: -SO 2 SCD>3 DU: + 1 point -SO 2 SCD<0 DU: -1 point If ∑ points ≥ 5 then an alert is triggered and an e-mail is sent to interested users SACS notification of exceptional SO2 concentration ================================================== Process date : 2005 05 15 Process time : 23:56:01 CET Instrument : SCIAMACHY No. notices : 1 Alert notice : 1 -------------------- http://sacs.aeronomie.be/alert/?alert=20050515_224502_001 http://sacs.aeronomie.be/alert/?alert=20050515_224502_001 Start date : 2005 05 15 Start time : 22:45:02.724 UTC Aver. long. : 167.7 deg. Aver. latit. : -16.9 deg. Aver. sza : 24.5 deg. Max. SO2 vcd : 41.3 DU Remark :

12. System development night 09:30 am GOME-2, IASI 10:00 am SCIAMACHY 01:30 pm OMI, AIRS IASI day SEVIRI (Europe) AIRS Development of an optimized SO 2 alert system (multi-sensors approach). MetOp-A Envisat Aura Aqua MSG Objectives: - increase the level of confidence of the alerts - reduce the ∆t between the eruption and the time when the alert is sent.

13. Algorithmic developments  Slant column retrieval  SO 2 absorption along the mean light path  Backround correction for measurements at high SZA  Estimation of the vertical column by applying an air mass factor  VCD=SCD/AMF The SO 2 vertical column is routinely retrieved from UV spectra using DOAS techniques: (UV sounders)

14. Algorithmic developments Tool GODFIT: Direct fitting algorithm that includes LIDORT as forward radiative transfer model and a ‘state-of-the-art’ Rotational Raman Scattering (RRS) code. Inversion capabilities  volcanic ash/aerosol retrieval  based on the different light intensity and RRS response of absorbing/non absorbing aerosols.  improvement of the SO 2 VCD retrieval (high SO 2 signal).  retrieval of the peak altitude of the SO 2 plume (particularly interesting for the VAACs). Alternative approach: direct multi-wavelength fitting

15. Simultaneous SO 2 column and plume height retrieval Direct fitting applied to GOME-2 Poster 103 J. van Gent et al. Strong SO 2 signal from Kasatochi (8 August 2008) Weak SO 2 signal from Eyjafjöll (9 May 2010) (preliminary)

16. Summary http://sacs.aeronomie.be/ NRT delivery and archive of data and images of SO 2 and aerosol/ash indexes from SCIAMACHY, OMI, GOME-2 and IASI (soon). E-mail notification of exceptional SO 2 concentrations exists for SCIAMACHY. On-going development of an optimized SO 2 alert system based on multi-sensors data (SCIAMACHY, OMI, GOME-2, IASI, AIRS, SEVIRI). Development of advanced retrieval algorithms to improve SO 2 (e.g., height of the plume) and aerosol/ash satellite data products.