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Open Access , 4 , 8 2 Discussions Sciences , M. Van 1 Natural Hazards Hazards Natural , C. Clerbaux 2 and Earth System System and Earth , and C. Zehner 7 , J. van Gent 3 en ff , P.-F. Coheur , K. Sievers 2 1 5936 5935 , J. van Ge 2 , O. Rasson 6 , D. Hurtmans 3 , L. Clarisse 1 , F. Prata 5 enhofen, Germany ff , R. van der A 1 , N. Theys 1 , P. Hedelt 5 This discussion paper is/has beenSystem under Sciences review (NHESS). for Please the refer journal to Natural the Hazards corresponding and final Earth paper in NHESS if available. European Space Agency (ESA-ESRIN), Frascati, Italy Belgisch Instituut voor Ruimte-Aeronomie – Institut d’Aéronomie Spatiale de Belgique Spectroscopie de l’Atmosphère, Service de Chimie Quantique et Photophysique, Koninklijk Nederlands Meteorologisch Instituut (KNMI),UPMC De Univ. Bilt, Paris the 6; Netherlands Université de Versailles St.-Quentin; CNRS/INSU, LATMOS-IPSL, Institut für Methodik der Fernerkundung (IMF), Deutsches Zentrum für Luft und Raumfahrt Norsk Institutt for Luftforskning (NILU),German Kjeller, ALPA, Norway Frankfurt, Germany 8 Received: 23 August 2013 – Accepted: 9Correspondence October to: 2013 H. – Brenot Published: ([email protected]) 31 October 2013 Published by Copernicus Publications on behalf of the European Geosciences Union. Nat. Hazards Earth Syst. Sci.www.nat-hazards-earth-syst-sci-discuss.net/1/5935/2013/ Discuss., 1, 5935–6000, 2013 doi:10.5194/nhessd-1-5935-2013 © Author(s) 2013. CC Attribution 3.0 License. P. Valks Roozendael 1 (BIRA-IASB), Brussels, Belgium 2 Université Libre de Bruxelles3 (ULB), Brussels, Belgium 4 Paris, France 5 (DLR), Oberpfa Support to Aviation Control Service (SACS): an online service forreal-time near satellite monitoring of volcanic plumes H. Brenot 6 7 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ects ff S and halogen 2 ,H 2 and ash. It combines ective, economical and 2 ff , SO 2 5938 5937 culty in mitigating volcanic hazard to aviation is ffi and is optimised to avoid false alerts while at the same 2 ect human health in the vicinity of the volcano, but the e ff ), which is a free online service initiated by ESA for the near , may also damage the aircraft (paint and windows) and create 2 1000 km from the volcano) and in the process cross major air routes. > and SO 4 SO 2 anti et al., 2010). A significant di ff Nine worldwide Volcanic Ash Advisory Centres (VAACs) have been designated is then used by aviation safety control bodies and by pilots via SIGMET (SIGnificant part of the InternationalInternational Airways Civil Volcano Aviation Watchcountries Organization (IAVW), and established (ICAO) several in international withAgency 2002 organisations the like by (IAEA), the co-operation the the InternationalFederation of International Atomic of Air numerous Energy Air Line Pilots’ Transport Associationsand (IFALPA), the Association International Geophysics Union (IUGG) (IATA), of and the Geodesy thedetails International World see Meteorological ICAO Organization (WMO). (2012). Forwhich The more together nine VAACs cover each theroute have whole on their globe. the own extent They area and make of movement advisory of responsibility, volcanic information ash available in en- the atmosphere. This information Thomas and Watson, 2010) iscontinuous particularly and relevant for global aviation monitoring safety,risk-free as of way. it volcanic enables the plumes in an e to advise civil aviation authorities in case of volcanic eruptions. These centres are sulphate deposits on andthe inside health the of the engines. passengers. The Inencounters the gases past of might there aircraft have also with been several volcanic be incidentsGu plumes dangerous as (Casadevall, a for 1994; result Casadevall of etthat, al., because 1996; of strong winds atlong high distances altitudes, ( fine ash canAs rapidly only be a transported small over numberground of the equipment, active the volcanoes on use Earth of are regularly space-based monitored using instruments (see Carn et al., 2008 and to aviation. The largest threatengines to and aviation cause them safety to is stall thatPrata, as volcanic 2009). a ash result Volcanic can of ash ash damagenavigation melting can plane (Miller systems, abrade and and Casadevall, windscreens, 1999; reduce damagesuch the as avionic visibility H equipment of and the pilots. Moreover, sulphuric gases, 1999). Volcanic ash and – to a lesser extent – sulphuric gases are also major hazards 2011), and can strongly a of a volcanic cloud may even felt far from volcano (Forbes et al., 2003; Baxter et al., Volcanic eruptions are known to emitand large amounts ice of aerosols particles) (silicatespecies). ash, sulphates and The gases compositiona (mostly complex of processes driven water each by the vapour, chemistrythe volcanic and Earth CO motion cloud of and magma is its insidecan the ejection unique, mantle sometimes at of as the have surface severe ithuman (Robock society. implications Volcanic is clouds and can for Oppenheimer, have the a 2003). theand significant Emission result atmosphere, impact climate, on life of atmospheric both chemistry on locally the and Earth, on a and global scale (Robock, 2000; Oppenheimer et al., time limiting the numbersuccessful results of with notifications 95 % in of case our notifications of corresponding large to true plumes. volcanic The activity. 1 system shows Volcanic eruptions: a threat to aviation safety is a realactivity concern. and, in Satellite combination measurements withvolcanic atmospheric plumes. are dispersion Here models, ideal tohttp://sacs.aeronomie.be we for track and present monitoring forecast the globalreal-time Support volcanic (NRT) to satellite Aviation monitoringdata of Control from two volcanic Service UV-visible (OMI, plumes (SACS, GOME-2)This of and new SO two multi-sensor infrared warning (AIRS, systembased IASI) of on spectrometers. volcanic the plumes, detection running of since SO April 2012, is Volcanic eruptions emit plumesvery of high ash altitudes.abrasive and Ash and gases easily rich in meltsper the plumes year inside atmosphere, and are their the potentially engines. ever hazardous at increasing With number for more of airplanes commercial than flights, 50 as the active safety ash of volcanoes airplanes is very Abstract 5 5 25 15 20 10 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2 en ff ), VAST cial tasks ffi ), whose general aims ) and the GMES Service http://savaa.nilu.no ) programmes (Van Ge http://www.evoss.eu http://www.temis.nl 5940 5939 http://www.gse-promote.org (concentration, altitude) from (but not limited to) satellite 2 ) that centralises the data (near real-time and archive) in the erent aspects of our work. ff ) and EU FP7 EVOSS ( Early detection of volcanic emissions. NRT global monitoring of volcanic plumes, with openQuantitative access and retrievals delivery of of data. volcanicdistribution) ash and (concentration, SO altitudeinstruments. and Ash particle data at size (Prata and high-temporal Prata, resolution 2012) has from priority. geostationary payloads Improved inversion techniques involving atmosphericdispersion models and removal for (Stohl forecasting et ash al., 2011). Validation of satellite observations. Accurate source term parameters:source emissions time-, for particle the size- entire eruptive and period. height-resolved ash – – – – – – Until recently, a policy of zero tolerance regarding volcanic ash was applied by ICAO http://vast.nilu.no http://sacs.aeronomie.be user and detail the di 2 Overview of SACS The Support to Aviationthe Control Data Service User isElement Element an (GSE-PROMOTE, ESA-funded (DUE-TEMIS, project developed within data products from satellite instruments operatingand in Thermal the Infrared UV-visible (OMI (IASI andto and GOME-2) notify AIRS) the wavelength users by ranges. e-mail Athe in system strategy case of has adopted exceptional been to volcaniceruptions, set-up emissions. detect we Here we demonstrate and present the monitor service volcanic and show clouds. the With information examples available to of the recent SACS for the monitoring and warning of volcanic plumes. It makes use of NRT ash and SO In this paper, wewhich give an deals overview with of the the first Support two to points Aviation listed Control above Service as (SACS) it is an automated global system on airlines (Cantor, 1998).concentration This thresholds regulation over has EuropeEyjafjallajökull changed in after April/May with the 2010 and the eruptions Grímsvötntotal introduction in closure of May of of 2011, the airspace as over ash Icelandic many bothupheaval European caused across volcanoes countries partial Europe and 2010). (IATA, or led The to introductiontranslates social of to and ash economic concentration important thresholds needsand and forecasting requirements services for (see improved Zehner, volcanic 2010). These ash needs monitoring are: using atmospheric dispersionon models, volcanic by cloudsground, making aircrafts from and use observatories, abovegeostationary all of pilot instruments). from all space reports instruments available and (mostly satellite information measurements imagery from from the METeorological Information) advisories. The VAACs provide volcanic ash forecasts form of maps (images) globally andlinked for to a set other of European pre-defined( regions. initiatives This such service is as also ESA SAVAA ( the National Aeronauticsof and SACS Space is Administrationof to (NASA). informing support The aviation the primaryactivity. control VAACs SACS objective organisations (key is about users( a the of free risks the service associated service) available with through in volcanic a their single o user-friendly web portal et al., 2007).partners: SACS the is BelgianNetherlands a Institute Meteorological collaborative for Institute (KNMI), Space project theGerman Aeronomy University that Aerospace of (BIRA-IASB; Center currently Brussels leader), (ULB) (DLR).the involves the and The following the the Royal SACS agencies/institutions: following project EUMETSATNational is (via d’Etudes also Spatiales the (CNES), indirectly O3M FinnishLaitos), supported Meteorological SAF Institute Norsk by (FMI, program), Institutt Ilmatieteen Centre for Luftforskning (NILU), Jet Propulsion Laboratory (JPL), and 5 5 25 15 20 10 15 25 10 20 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | and and 2 2 ). The 2 − erent data ff erent products erent overpass ff Vertical Column is more reliable ff 2 2 is often a good proxy moleculescm 2 16 erent trajectories because 10 ) and aerosol (ash) related ff 2 × and ash observations). Figure 1 2.69 2 = has strong and distinctive absorption to follow di 2 2 erential absorption by ash between two ff 5942 5941 en et al., 2007, 2008) and GOME-2 (Rix et al., ff concentration integrated along the vertical axis 2 , pointing them to a web page with relevant 2 ) is an approximate value at nadir. A description of the di 2 erent sounders that SACS currently uses and their local overpass time. ff column retrievals from UV-visible sensors (SCIAMACHY, OMI, GOME-2) 2 erences in injection altitudes. For these reasons, SACS is providing both SO data products to trigger and issue plume notifications. SO retrievals of SCIAMACHY (Van Ge ff 2 2 The retrieved quantity from the three algorithms is the so-called SO A notification system has been set-up to warn people (by email) in case of SACS delivers global data sets for sulphur dioxide (SO and is generally expressed inSO Dobson Units (1DU hence can only measure duringgeometry, daytime). except The observations for areand SCIAMACHY, done limb in which (not nadir had viewing usedspectrum here). alternating is Once also viewing a acquired.UV modes All day, wavelength a three range in (240–400 direct instruments nm), nadir measurement havebands. where The spectral SO of spectral channels the resolution covering in solar the the irradiance UV range is 0.2–0.6Density nm. (VCD). It represents the SO from the five instruments listed in Table 1 and3.1 their main features. SO The SCIAMACHY, GOME-2measuring solar and light backscattered OMI by the atmosphere instruments or reflected are by the UV-visible Earth (and spectrometers and when it is presentindicator of in volcanic the activity. upper Therefore, the troposphere/lowerSO SACS stratosphere system it at is present a onlyfor more uses volcanic robust satellite plumes and thereforeThis possibly being of said, volcanic not asheven all (Thomas then eruptions and it Prata, are is 2011). accompanied notof by di uncommon detectable for amount ash of andaerosol/ash SO information SO in NRT. In this section, we briefly present the di The detection of volcanicof ash is the far from current trivial,channels, which satellite especially can for algorithms yield dispersed falsethan plumes. use detection Most ash in di (e.g., the presence desert of dust). absorbing aerosols Conversely, other satellite detection of SO 3 Description of satellite data products used by SACS (resolution in km products used in the SACS system is given in Sect.exceptional 3. concentrations ofinformation on the SO location ofnotification the service plume. Users which also compilesData have archives notifications the contain possibility of the to on-goingJanuary consult observations or the 2004 starting past until from September April eruptiveJanuary 2002 2012 events. 2007 for for for GOME-2, AIRS, SCIAMACHY, and from from from September October 2007 2004 for for IASI. OMI, from data from SCIAMACHY/Envisat (Bovensmann etstill al., be 1999) consulted. for which Tablecharacteristics: 1 archive data presents satellite can a platform, summary datatime, of type spatial the and SACS availability, resolution, equatorial productsswath retrieved widths, local and and quantity, overpass global their coverage. data main Note that provider, the size units, of the delays footprint of of each instrument retrievals, AIRS/Aqua (Aumann et al., 2000, 2003;2006), Hofstadter et al., GOME-2/MetOp-A 2000), OMI/Aura (Munro (Levelt et2009; et al., Hilton et al., al., 2006) 2012).as All and soon SACS as IASI/MetOp-A data retrievals the (Clerbauxshows are data the available et process in di NRT al., allows (whichIt to means shows retrieve the SO advantagetimes of in combining multiple a sensorsplumes single on which the system have global scale. as di Note it that until allows April 2012, the the NRT reliable SACS system and also used timely monitoring of volcanic and prediction. to volcanic eruptions fromwriting, measurements by SACS space-based is instruments. basedto At sound the on time atmospheric polar of composition sun-synchronous and satellite for instruments meteorological and widely scientific used applications: are to define and demonstrate an optimal system for volcanic ash plume monitoring 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1 1 − − VCD 2 resides 2 , 1327 cm 1 − (with gaps) and absorption band 1 VCD is 5.2 DU as 2 − 2 erent from SCIAMACHY ff are provided in NRT by the 2 6 km) and lower stratosphere ∼ , and a second step to adjust algorithm (see details in Clarisse 2 2 . The AIRS instrument is an echelle 1 − (and other atmospheric gases) to yield set corrections are generally applied, to 2 ff retrievals are processed by BIRA-IASB (asymmetric stretch) SO 2 3 5944 5943 ν retrieval is slightly di N has been chosen for the 3 instruments, and . The AIRS L1 data are provided in near real- ◦ slant column as an intermediate step. Note that 2 1 ). The IASI SO 2 − . The instruments are operating in a nadir view with -line radiative transfer calculations (see details in concentration integrated along the mean optical light 1 ff band, following the Linear Fit algorithm (Yang et al., 2 − 2 erent overpass times, we can see a very good spatial (with no gaps) with a spectral resolution of 0.5 cm ff ), and the SO 1 − and 1385 cm images displayed in SACS all use the data assuming lower erential Optical Absorption Spectroscopy technique (DOAS, Platt 1 based on o erent scenarios of emissions: planetary boundary layer (typically ff − 2 ff 2 . For AIRS, three wavenumbers are used (1395 cm 1 − ), while the IASI algorithm is based on measurements around 1 − algorithms from OMI, SCIAMACHY and GOME-2 are able to detect similar vertical column is obtained using radiative transfer calculations that account , 1372 cm index retrievals from thermal IR sensors (IASI and AIRS) 2 2 1 VCDs, a fixed latitude of 19.4 plume is moving westward. This example shows and confirms that SO 2 slant column, i.e. the SO − 2 2 2 VCD images from SCIAMACHY, GOME-2 and OMI for an eruption of Kilauea http://cpm-ws4.ulb.ac.be/Alerts plumes. Despite the di vertical column estimation is provided on three hypothetical atmospheric layers patterns for modest and strong eruptions. Figure 2 shows that the measurements 2 2 2 2 15 km). The SO Both IR instruments cover the strong The SO The SO ∼ Prata and Bernardo, 2007).ULB The ( retrievals from IASI SO around 1362 cm and 1328 cm 1408 cm time by NASA’shttps://urs.eosdis.nasa.gov Earth Observing Systemusing Data the algorithm and fromwith Information NILU. a System The first (EOSDIS, retrievalthe scheme step amount of to AIRS of identify is SO a pixels two-step that process contain SO a spectral resolution of 0.5–2typical cm footprints (circular to elliptical depending15 km on the diameters position (at on nadir), thespectrum for swath) of of IASI 12 and the and AIRS outgoing(and respectively. thermal Both hence can sensors radiation operate measure emitted during the by both day the and Earth-atmosphere night). system SACS images. 3.2 SO The IASI instrumentis is from a 645(apodised) and Fourier to a transform 2760 spectral cm grating sampling spectrometer. spectrometer of covering The the 0.25 cm range spectral between 650 coverage and 2665 cm measurements from UV-visible instruments allowvolcanic a emissions good even estimation for and suchrecorded monitoring a by of small GOME-2 eruption during (theproducts highest this for SO day). all Note UV-visible thatadditional instruments the information. are operational Note cloud that also cover the available fraction measurement on times the are SACS indicated webpage in as UTC on all the SO agreement between the VCD values is found, especially taken into account the fact stratospheric plumes. SO (SO volcano in Hawaii,SO 17 May 2008)correspondence are of able the location tothe of consistently SO the observe plume between smallthe the measurements (and 3 have been low) instruments. plotted To as compare a function of longitude (Fig. 2d). A fairly good and because we have no knowledgeSO what this altitude isrepresentative prior to of the di measurement, the the first km above( the surface), upper troposphere ( 345 nm) in and outside2007) and the it SO does notfor retrieve all an instruments, SO several backgroundensure and geophysical o consistency of the data. for important parameters influencing theangle, viewing UV angles, light clouds, path atmospheric inAs absorption the the and atmosphere: measurement scattering, solar surface sensitivity zenith albedo. strongly depends on the altitude where SO and Stutz, 2008) whereare all fitted measurements to in laboratory athe absorption wavelength SO data range of from SO 315path to in 326 nm the atmosphere.and The GOME-2 OMI SO in that it uses only a small number of wavelengths (between 310 and 2009, 2012) use a Di 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2 erence vertical ff 2 erentiate it ff 5946 5945 images from SACS after the beginning of the 2 ects, including molecular Rayleigh scattering, surface ff OMI, GOME-2) The UV wavelengths used are 340 nm and 380 nm for SCIAMACHY and GOME- Figure 3 shows IASI and AIRS SO the first instrument onat a the polar start orbiting of satellite thethe Grímsvötn able IASI eruption to at ash clearly 20:45displacement UTC detection distinguish of on ash at 21 the emitted 10:30 May ash UTC 2011.from cloud Figure GOME-2 on during 4b and 22 the shows OMI). next May. 2 We days can (ash see detected in by AAI Fig. retrievals 4c and d the high confidence detections).ash The candidates third tohigh steps low confidence and considers detections. medium spatial(because The confidence of context procedure step detections to 2), ensures in whileneighbourhood promote a at the of the very neighbourhood high same low time confidence of presents identifying false detections the as AIRS detection (because much detection as of rate of possible steps ash ash at 1 in 03:40 the and UTC on 3). 22 Figure May 4a 2011. Note that IASI was infrared sounders tofrom detect other airborne volcanic aerosol ash (includingproducts windblown used with sand). in The a SACS IASIfor are and high details). AIRS based The sensitivity ash first on step index a and calculatesthe the three-step di relative measured process distance spectra (weighted (see projection) and Clarissethese between fixed et distances, ash al., only spectral 2013 those signatures.ash observations Based candidates). on are The the second keptcertainly magnitude step which ash of finds by are imposing the likely very subset to strict of criteria be observations based ash on which absolute (called are distance almost criteria (called Grímsvötn eruption is clearly identified. 3.4 Ash index retrieval from theClarisse thermal et IR sensors al. (IASI, (2010, AIRS) 2013) have demonstrated the potential of hyperspectral thermal of AAI images from the UV-visible sensors GOME-2 and OMI. Ash emitted during the the ocean and therefore ad-hoc flags are applied. Figure 4c and d show an example separates the spectralaerosols contrast from at that tworeflection, of ultraviolet other gaseous wavelengths e caused absorption,Torres by et and al., absorbing aerosol/cloud 1998). scattering (Herman et2, al., and 1997; 354 nmcovered and areas and 388 nm isHowever, for performed the OMI. equally final well AAI Note over products that ocean are AAI and sensitive land retrieval to (except is calibration over possible issues ice). and over sunglint cloud over The Absorbing Aerosolaerosols Index in (AAI) theanomaly, indicates or atmosphere. simply the aerosol It presence index.part is Because of of the often the presence elevated AAI of named absorbing detection, ash the can SACS be provides residue, the these dominant the products in spectral near contrast real-time. The AAI eruption of Nabro’s volcano (Eritrea).plume IASI at was 06:25 a.m. the and firstNevertheless 08:05 instrument a.m. to UTC these observe (for observations the two consecutive SO coverage did orbits) of the on not plume 13 was June coverillustrates possible 2011. the by the combining benefit full IASI of with plume.receiving AIRS our the measurements. At multi-sensor This data approach. 10:50 was a.m., As about 1 a a h50 side and full note, 13.3 h30 the for delay IASI time and Absorbing for AIRS, respectively. aerosol index retrievals from UV-visible sensors (SCIAMACHY, column by making use oftemperature and a humidity large profiles. These look-up-table are andTo only ensure available EUMETSAT for a operational data maximum pressure, with amount L2 of information. index IASI is data, used only in the the brightness NRT temperature treatment di of SACS. et al., 2012) also involves the conversion of the measured signal into an SO 5 5 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2 2 2 S, ◦ down 2 ects the ff www.knmi. concentrations. detection alone). 2 2 500 km of altitude). Low- ∼ is limited to the atmospheric 2 -line schemes to correct for the row ff is present at altitudes where airplanes ected by clouds and instrumental noise ff 2 ected rows are not treated in SACS, leading er from a so-called “row anomaly” since 25 ff and ash emissions ff 5948 5947 set by about 500 km from the rotational axis. 2 ff W (the precise strength, shape and size of the SAA ◦ ects particular viewing direction angles, corresponding to ff retrievals are also a 2 ). Currently, the a images and evolves as the instrument is degrading over time. 2 products 2 by these two sensors means that SO , the vertical sensitivity of IASI and AIRS to SO 2 2 retrievals and results in noise artefacts, as is visible in Fig. 5a and b. Thanks to 2 ected by the SAA than SCIAMACHY or GOME-2 (as can be seen Fig. 5c). The OMI instrument has started to su ff rows on the CCD detector. The row anomaly has increased over time (see SO its design which givesa it better protection to radiation than other sensors,June OMI 2007. is This less anomaly a America and the Southern Atlantic Ocean:and it between lies longitudes roughly 0 between and latitudesvaries 5 80 with and the 40 seasons). This dipand in cosmic the rays Earth’s to magnetic penetrate fieldorbiting lower allows satellites, into charged particles such the ionosphere asradiation (at Envisat, belt Aura in and theimpact MetOp-A, SAA-region. on pass Upon daily passing thedecreases through the detector, the inner the causing quality belt, inner higher-than-normal charged of particles the radiance may measurements, values, notably which in in the turn UV. The SAA a The Earth’s dipolar magneticAs field a is result o ofcharged this, particles) the inner is VanThis on Allen region one belt is (doughnut-shaped side named regions the closer of South to high-energy Atlantic the Anomaly (SAA) Earth’s and surface it than covers a the part other of side. South 3.5.3 Known anomalies impacting the data But it should be notedash that plumes because are of often the not strict detected conditions in of the step current 2, implementation. low concentration 3.5.2 Aerosol products Besides themeasurements fact from UV-visible sensors that are sensitive(desert to the all dust, types biomass of aerosolselective absorbing burning aerosols for products aerosols, ash. However, volcanic theis are ash) combined highly detection selective and qualitative of for are the bothNote volcanic products therefore elevated plume that aerosol not (in the and fact (indexes), ash purely SO even more product than of SO IASI and AIRS sensors yields very few false detections. pollution hotspots are confinedSiberia), to the a SACS system limiteda can number general comment, easily of SO be regions(especially tuned (China, at to high South solar avoid Africa, zenith falseup angles in notifications for the there. the SO As UV sensors). The latter generally shows layers above 3–5 km dependingseem serious, on but the in the humidityof context vertical SO of profile. aviation it This isspend limitation actually most an might of advantage their as travelthe the time. detection IR This fact sensors combined a withsensors central four are overpasses component characterised per of by day a the make to relatively the SACS good system. surface. measurement While As sensitivityrenders this a for the allows complement, SO measurements monitoring the sensitive of to UV low anthropogenic altitude emissions. volcanic As most degassing, of it the also SO 3.5.1 SO Because of competing wateras SO vapour absorption in the same IR wavelength window 3.5 Limitations of satellite products in detecting volcanic plumes 4 Global monitoring of volcanic SO In this sectionemissions we and present the strategy results adopted from to warn the users SACS of exceptional global SO monitoring system of SO to a reduction inanomaly the exist (e.g. data Yan coverage.processing. et Several al., o 2012) but are not implemented yet in the NRT data- nl/omi/research/product 5 5 25 15 20 10 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2 2 plumes from 2 erent characteristics, erent overpass times, ff ff column for more than half of the 2 ected by the SZA limit criteria (day and ff concentrations from the five instruments 2 5950 5949 notifications 2 erent notification threshold values have been ff column which must exceed the relevant threshold. An 2 notification 2 erent zones and time durations. A set of two parameters has been ff . It requires two steps: (1) proper establishment of warnings criteria for the 2 notification from UV-visible sensors 2 erent sensors, (2) combining the information from the sensors in one system. Another limitation of UV-visible sensors comes from the South Atlantic Anomaly (see Also apparent is the higher sampling rates for high-latitude regions due to ff for measurements close tomore a given limitation volcano of (distances UV-visible less sensors than is 300 that km). Finally, they one are sensitive to anthropogenic SO Table 3 and Fig.observations 7), must also for exceed whichwhen both the the criteria threshold observed are value. fulfilled.plume SO An A from illustration the notification Copahue is is volcano given (23 in generated December Fig. only 2012). 7 forSect. GOME-2 3.5.3). for an To avoid SO falseconsidered notifications (see in Table 3). this Note also region,small that a special eruptions more settings and strict are used degassing, threshold for value in SO is that the system considers lower threshold values The instrumental noisenotifications. on For the this UV-visibleobserved data reason, value is a for a firstadditional the limitation criterion selection SO and is based criterion can on lead the is neighbouring to based pixels false (inside on a threshold the radius, maximum see The criteria for detectionhas of been exceptional derived from SO the analysisconsidered). of historical results Each (see Table 1therefore instrument for the for data and periods eachestablished. retrieval Note that, data method even though source ithere has because no di it more di has provides been data,SACS used SCIAMACHY archive. in is the included past and notifications based on itsSO data are in the retrieval failures) or overly frequent/redundant notificationsplumes). (caused by highly dispersed 4.2.1 Criteria for SO Particular attention is given to the avoidance of false notifications (due to noise or for SO di coverage of D-E-Fthe zones coverage depends of on IcelandNevertheless, because the the is IR day less sensors are ofnight good not measurements), a year. the (due coverage For of to the example high-latitudeof the regions overlapping in always SZA orbits takes advantage December, over limit North for and South UV-vis Poles. instruments). 4.2 SACS strategy for volcanic SO Here, we detail the implementation of the global multi-sensor notification system a 24 h interval. Theand 30 percentage % value for drops periods respectively to of 99.5 %, 12, 8, 95 %, 6,overlapping 90 4, orbits. %, 3, This 75 2 %, is and 60 particularlywill 1 %, h. be interesting 50 sampled for % e.g. Icelandic every 2 volcanoes h (zone 50 E) % of that the time (see Table 2). Note that the geographical Fig. 6a) and we have estimated,areas based that on have data been of observedGOME-2, October at IASI, 2012, AIRS). least the The percentage once calculation of bycoverage was the one of done of the for several the Earth time satellite by intervalsresults SACS instruments (see after for (OMI, e.g. 8 the the h di ofevaluated: monitoring pxl in is Fig. the 6b). percentage Table ofand 2 the presents max region the of is interest the sampledwith by four maximum the instruments, number SACS SACS system; of monitors in overpasses. near From real-time Table any 2, location in it the can world be within seen that It is important to knowsystem. precisely Because the of time the andsome space use geographical sampling regions of of are polar-orbiting the observedrevisiting SACS more satellites frequency monitoring frequently of with than SACS, di others. we To have evaluate defined the seven geographical latitude zones (see 4.1 Temporal and spatial sampling 5 5 20 25 15 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ◦ ). The value, by 30 2 ◦ erent parts are described in more detail ff ected by instrumental noise, the SAA, or ff in latitude. Figure 9 shows the locations (and 5952 5951 is used for each UV-visible sensor depending ◦ observations (from one of the instruments), the ff 2 http://sacs.aeronomie.be/alert/subscribe.php erence of Brightness Temperatures (called DBT and ff notification’s web page 2 warning service relies on pre-defined geographical regions. SACS sends 2 signal along with the date and time of observations (UTC), a flag indicating and ash images. As soon as a notification is issued, the related region is flagged notification for a dedicated region notification from thermal IR sensors 2 2 2 2 Note that a solar zenith angle cut-o to users who subscribed to SACS ( notification for thiscan region possibly (meaning become noprocessing ON. notification time. The If since systemenables the compares 12 h), to delay the provide the is timely time warningnotifications less information of (maximum to than status one observations the notification 8 users with h, per and region the the also and notification per toE-mail 12 avoid is h). notification issuing issued. too This many set-up Important information related to the warning is gathered into a notification sent by email “ON”. Check of the warning status The second step is to check the “warning status” of this region. If there is no on-going SO regions are used in the near real-time monitoring and archive services to display the SO As soon as SACSfirst harvests new step SO isa the volcanic analysis eruption, of thereFor are the this potentially reason, data multiple it using warningsplus has generated two the been polar by criteria decided regions the toassociated polewards defined system. consider of name/number) in 75 of a the Sect. set 62 of 4.2.1. regions world After of regions the of SACS 30 system. Note that the same a notification to usersof as 12 soon h, as a a plume(to new is volcanic detected avoid plume again sending is inwarning redundant the detected. system same If information). is region within An presented no a in newbelow. illustration period Fig. notification of 8. is The generated the di SACS multi-sensors pollution. For IASI, rather than consideringapply directly threshold on values the based measured on Di expressed VCD, the in criteria Kelvin [K]),and and VCD) is used therefore are straightforward. givenalmost The in no threshold Table false 3 notifications. values for (DBT respectively IASI and AIRS,4.2.2 and they produce SACS multi-sensor warning system The SO areas (West China, Central North Russia and South Africa). SO IASI and AIRS are much less or not at all a emissions. To avoid false notifications, more strict criteria are used for some specific An example ofnotification a web is page shownMetOp-A generated in passed over by Fig. this area. SACS 11. Thenotification using page This shows (time GOME-2 a of notification box measurement, data with was the location for information of sent of a the the email to warning, specific SZA, the maximum SO users 1 h01 after on the day of thecoverage while year. The limiting values the have increase been in determined the noise empirically (instrument-specific).Dedicated to SO have the best email notification (see alsonotification and the the example instrument, the showna region in link number, to some Fig. a details 10) dedicated aboutSO web contains: the page processing, the generated time bywhether the of a system, cloud the coordinates correction of has the been maximum applied or not, and finally the solar zenith angle. 5 5 25 20 15 10 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2 emissions from 2 and aerosols/ash 2 signal and ash in the region 2 , and a Google-Earth file, see erent webpages. 5954 5953 ff ). For the UV-visible instruments, there is also a link to http://gmt.soest.hawaii.edu image, one can find two links to the same image but using notifications over Europe in 2004. During the first week of 2 2 notification 2 brightness temperature index image there is also a link to the SO 2 warning archive 2 erent mapping tools (interpolated image using the Generic Mapping Tools from the ff November, an eruption occurredthe eruption in fell Iceland as (Grìmsvötn far away volcano). as Volcanic mainland ash Europe and from caused short-term disruption of period. The main volcanicState activity of detected Papua byDemocratic New Republic SACS Guinea, of in Congo the 2004 (DRC),Rwanda, as archipelago is the shown of in in DRC Fig. the thevolcanoes, and 13a. Independent Republic The including Uganda borderland of Mount between iserupting Vanuatu, one Nyamuragira on and 25 of and May the 2004. the MountNyiamuragira Details from most about Nyiragongo the 1979 active satellite which to monitoring regionspresents 2005 of were also containing can SO several both be eight SO found in Bluth and Carn (2008). Figure 13a in a quick andsmall user-friendly volcanic eruptions way. which Note might that not our always lead system to4.3.1 also a notification. allows the Notifications monitoring from 2004 of to 2006Data (SCIAMACHY, OMI, and from AIRS) the SCIAMACHY, OMI, and AIRS instruments are available for this 4.3 Nine years of data andAlthough notifications the archive multi-sensor notification systemyears is only of operational since historical Aprilservice. data 2012, This nine have section been presentsusing an reanalysed the overview for of five thenotifications all sensors. is the development notifications shown of For identified withSACS the each by a portal, warning SACS allows highlight year any of (from interested the person 2004 main to events. investigate to historical This eruptive 2012), tool, emissions available an on image the of all the of the warnings isthe an user interactive can map.interactive visualise When tool, the moving a images the commonavailable corresponding cursor with list to the on relevant with the a links all to warning. warning the the In point, di warnings addition (chronologically to sorted) this is also delay of 12 h separates the time between two warnings, as explained above. The map side-by-side. Below the SO di University from Hawaii, see and the use of cloud data in calculations), and the images of SO updated on the SACSinstruments web of site. interest, The for a warningof given subpage all month/year and allows the to the corresponding visualise users warnings a to map (see with select next the the section). location For a given region, a minimum and ten hours after thisand notification IASI from took GOME-2, place. two others confirmations from AIRS Update of SO As soon as a warning is detected by the system, the warning archives are automatically Confirmation of SO For the example shown in112 Fig. 11, (see IASI also Fig. detectedjust 12) SO 3 min and after acted theNo as one notification of a has GOME-2, been confirmation. whichon sent In took GOME-2, to place fact the but at the users, thenotification 23:42 UTC, as box processing dedicated as for there of the show web already IASI Fig. IASI page was warning 10. a using was has the notification been same based displaying automatically template. updated Note that with two the VCD image. As a complement,to a a map listing showing including the morepage. volcanoes information Furthermore, in about a each the direct of region link them) (withall to is a the corresponding also link near SACS provided real-time images on monitoring (for thisto web all web page data instruments), is providers), and given for a with the link region to considered. the data (files or link http://www.google.com/earth the corresponding cloud coveraddition fraction to (CCF) the image. SO In case of a IASI notification, in 5 5 20 25 15 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1 − gh ected ff 12 10 × kg and a volume and ash reached 11 2 and using dispersion 10 3 × − of gas with a 2 km long curtain of 3 usive eruption, a huge amount of gas ff 5956 5955 observations from the GOME-2 and IASI instruments became emitted during the initial eruption travelled rapidly northward over 2 2 over the 35 h release period. Note that at this time of the year, the thermal c into Iceland. Assuming an ash density of 2200 kgm 3 ffi c from the United States to Asia and causing ash falls on Alaska’s Unimak IASI) ffi The Jebel al-Tair eruption started unexpectedly on 30 September 2007 after 124 yr In 2006, volcanic activity has been detected by SACS (Fig. 13c) in the Andes The volcanic activity in DRC (Galle et al., 2005) and in Galapagos and Vanuatu plume reached the2008; low Clarisse stratosphere et at al., an 2008; Yang altitude et of al., 2009). about The 16 km eruption of (Eckhardt Piton et de al., la Fournaise (although not all events are relevant forvolcano), aviation), notably the in Papua archipelago New Guinea(Tungurahua (Rabaul of volcano), Vanuatu the (Ambrym Boninand Islands and in of Ethiopia Lopevi Japan (Manda volcanoes), (Fukutoku-Okanoba),Jebel Hararo). al-Tair in Italy The Island (Yemen) (Etna), two Ecuador and largest at eruptions Réunion Island of (France). 2007 wereof observed dormancy. at SO Egypt and eastward over Pakistan and India (Clarisse et al., 2008). The volcanic observed by our system forNorthern some Kurile volcanoes Islands of and the inKliuchevskoi Russian Kamchatka), volcano as Federation started shown (located in in another Fig. the to eruption 15a. experience In cycle. January the On 2007, largest 28 the air explosions June, so tra this far volcano recorded began Island. in Volcanic activity that has eruption also be cycle, monitored disrupting by SACS in many other regions on Earth (22 and 24 May, Fig.by 14). the Note row anomaly that and for was this still date, able the to4.3.2 OMI provide sensor global coverage. was Notifications not yet from a 2007 to 2012 (SCIAMACHY,Since OMI, AIRS, 2007, GOME-2 SO available and and have been included in SACS. Volcanic emissions in 2007 have been a large explosion, producing anThe ash movement column of of this about volcanic clouddrifting 18 km has westward and height been causing monitored (Prata diversion during et ofOMI 23 al., many sensor days 2007). planes. measured (see The a Fig. 20 VCD 14), May, at uprapidly 17:02 to UTC, dispersed 122.2 the DU. the Several days volcanic after cloud the eruption, on the the wind north-east and the south-west directions distance (more than 18 000 km westward). A large dome collapse was accompanied by pass over Pakistan andBritish India; Overseas (3) Territory) the released 20 a May volcanic eruption cloud of which travelled Soufrière over Hills a (Montserrat, very long Cordillera (Colombia and Peru),parts but of the the world: threevolcano (1) strongest (Papua on eruptions 6 New occurredstratosphere. October, Guinea), a in Several large notifications other sending explosive havecloud a eruption been took traveling plume issued place by westward; of atA SACS strong Rabaul (2) gas showing eruption began the and the in volcanic 2007). the ash The Nyamuragira night volcanic of cloud up volcano the initially 27 moved to was November north-eastward (see to the e.g. finally also Prata travel to lower and active the Bernardo, west and in 2006. cloud with an estimatedlava volume fountains of (Geist 150 et al., millionsand 2008). m particles During was this ejected e inan the altitude low troposphere. estimated Theatmospheric below plume emissions of 5 of km SO this (Yang volcano ceased. et al., 2009). At the end of October 2005, observations) to monitor the volcanic plume. has continued in 2005eruptions as are can be alsoOkanoba seen visible: volcano, in located (1) Fig. 6(about km the 13b. northeast The 1300 submarine km signatures of south-west eruption of theGalápagos, of Ecuador. two pyramidal of After Tokyo); additional island 26 the (2) yr ofan being the Japanese Minami-Iwojima active inactive fault, eruption and the Fukutoku- volcanic six of activity monthswith of the after the a Sierra an Sierra Negra fissure earthquake raised Negra on opening again on volcano, inside 22 October the 2005 rim of the caldera. This eruption emitted a volcanic airline tra models from the VAACs, Witham etfor al. the (2007) larger gives plume, an that emission correspondsof to up 0.15 an to km erupted 9.50 mass ofIR 3.3 sensor (AIRS) was the best instrument (best coverage and time laps between 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | . 2 2 1 − s 3 images. c across 2 c over the ffi ffi observed by UV-visible into the atmosphere for 2 2 emission shows a budget 2 cloud observed on the afternoon -rich cloud (up to 676.4 DU on 8 2 0.2 Tg by Haywood et al. (2010). 2 ± ). The ash images from IASI (showing ◦ and ash cloud are well co-located (see lla volcano erupted on 3 November. This 2 ffi 5958 5957 by 0.25 ◦ notifications identified by SACS for the year 2010. ected regions Fig. 15b). was estimated for this day by Tulet and Villeneuve ff plume was emitted two days before and was observed 2 2 1 cloud from Kasatochi as observed by IASI on 10 and 11 − 2 image). We can see that the ash detection (with a low level 2 ected by volcanic activity. The 2010 eruptions of Eyjafjallajökull ff and ash clouds observed by AIRS are shown in Fig. 17 (ash image plume was estimated to be 1.2 clouds show a similar pattern on 10 August (see Fig. 16a). Note that 2 2 2 ected the radiative budget of the atmosphere (Haywood et al., 2010). and water vapour creating sulfides or sulphuric acid. In May 2010, during ff cially over in October 2010, when snow falling on the glacier did not melt 2 ffi Figure 18a shows all the SO Three major eruptions that occurred in 2009 were identified by the SACS warning Two months after Kasatochi eruption, Dala Figure 16 presents the SO The SACS notifications of 2008 are presented in Fig. 15b. Besides a few eruptions between SO volcanic ash cloudswestern over and Europe, northern causing Europe2010). enormous over an Additional disruption initial localised to perioddeclared air disruption of o six tra continued daysanymore. in into From April May 14 2010 to 2010. (Zehner, volcano 20 The erupted April, (see ash eruption covered Fig.from was large 19 AIRS areas with and of IASI images northern from ofclosed 14 by Europe the to the when authorities. 17 level During the April). of theseand Most days, confidence the of IR quantity of the of satellites airports ash SO of was detection Northern low Europe (less were than 5 DU), possibly due to local chemical reactions of 17 June. TheIsland. No ash ash was cloud detected detected by AIRS by over AIRS the PacificMany is ocean. regions located were over a volcano the in Sakhalin Iceland were Russian relatively small, but unusual meteorological conditions brought This eruption, which was onesignificantly of a the 10 largest stratosphericImages injections of in the the SO lastsuperimposed 50 over yr, the SO of confidence) over the RussianOn land on the the morning north (UTC ofFig. time) the 17a). Note Sea of that of 16 the Okhotsk firston June, is SO the SO an West artefact. coast of USA. Figure 17b shows the SO service (Fig. 15c):islands, and redoubt Sarychev volcano volcano in(11–19 the in Kuril June islands. 2009) Alaska, The emitted explosivea eruption Fernandina a range of huge Sarychev of volcano amount altitudesmass in of of of ash Galápagos 10–16 km the and (Carn SO SO and Lopez, 2011; Clarisse et al., 2012). The Canada is an artefact inThe the analysis volcanic of plume the emitted spectrumAugust). by and We the Kasatoshi can process was see of on a ashcloud 11 SO detection. August (see that Fig. the 16b). detected ash cloud is smaller thanvolcano, the located SO in the AfarAle region Range. of We can Ethiopia,largest see is in observed one Fig. in of 15b the Ethiopianotifications that six in over a volcanoes historical India few in and times, days the the the after south Erta volcanic this of cloud China. eruption, generated which six was SO the August (interpolation with a gridthe of level 0.25 of confidence of theThe detection) ash have been and superimposed SO over theash SO observed with a low level of confidence over the south of Alaska and the west of on the Galapagos islands(Ethiopia), (Cerro the Azul two volcano) mostKasatochi and significant volcanoes the (Aleutian explosive Islands, eruption eruptions Alaska, ofThese happened USA), two Dalafilla respectively, at eruptions in volcano have July the been and Okmok studiedin August. extensively and the and more literature information (e.g. canClarisse be Prata et found et al., 2011). al., These 2010;North strong American Karagulian eruptions continent caused et (see a al., a real 2010; threat to Krotkov air et tra al., 2010; eruption in 100 yra in fissure produced this a lava region flowA that (Deroussi degassing reached et the up sea al.,(2011). with to a 2009). Their flux 1800 kgs estimated On study at 2of 100 of m 230 April, kt. the This the temporal eruption stopped opening evolution on of of 1 the May. SO (Réunion Island) started during the night of 30 March 2007. This was the largest 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2 was measured (up in the atmosphere, and ash cloud (see 2 2 2 detected by IASI and AIRS on 2 plume observed by IASI during the night of - and ash-rich plume was estimated to be and ash clouds were collocated. Afterwards, 2 2 5960 5959 2 and ash measured by IASI on 5 November. notifications (see Fig. 18a) and allowed a good 2 2 usive phases took place and released a mass of SO cloud, which travelled over Canada and came back over ff image. A null, low, medium and high level of aerosols/ash 2 2 and ash clouds were observed by IR sensors respectively notification archives span, this eruption is the most ash-rich 2 2 c occurred. On 1 September 2012, an explosive eruption took ffi were monitored respectively by IASI during 10 and 15 days after the 2 c of the Southern Hemisphere during the month of June 2011 in Chili, ffi was ejected northwards while the ash cloud went to the southeast (see GOME- 2 Figure 18c shows the SACS notifications for 2012. Continuous activity was recorded During the night of 12 June 2011, the Eritrean Nabro volcano started to erupt (see On 4 June 2011, the eruption of the Puyehue-Cordón Caulle volcano started. Out The largest number of notifications of the SACS system to date occurred during The strongest eruption of 2010 was the one of Merapi on 3 November on the Island place at Bezymianni volcano (Kamchatka), producing an SO volcanic cloud. We can13 see and in 14 Fig. June. 3 Figure15–16 the 23 June. cloud shows The the of amount SO SO oflargely ash undetected emitted by by IASI Nabrowas and still for AIRS), detected this while by eruption the IASI was ash in very emitted Fig. low 23. by (and theat Puyehue the volcano Nyamuragira volcano (DRC). Summitby eruptions of SACS Etna (Italy) in were alsodisruption detected January–April of 2012, air tra and again in July–October 2012, but no strong Fig. 3). Thisthreating explosive international eruption routes ejectedvolcano from a spewed the huge a Far amount volcanicand East of plume the to SO Middle across East. Europe. the Satellite On route information 14 of was critical June, many in the flights monitoring Nabro over the East journey of Africa the the volcanic cloud disperseda and few circled day, the around cloud the offor this ash South particular covered pole the eruption, (see main thatlimited part Fig. occurred coverage during of 22). and Southern the Within Austral high IASI winter,volcanic latitudes. and the Note plume. UV AIRS that The sensors were had SO theduring only 3 sensors and able 5the to weeks. track air The globally volcanic tra the ashArgentina, emitted Uruguay, Brazil, by South Puyehue Africa, consequently Australia and disturbed New Zealand. was under the limit of detection 3 days after theof start the of nine the years eruption. therecorded SO by our system.the The first volcanic two cloud days emitted of this was eruption, an the ash-laden SO plume. During Europe, was monitored during 3 weeks. The ash cloud, which travelled over Europe, Grìmsvötn eruption. The SO the year 2011 (Fig.Icelandic Grìmsvötn 18b). volcano (21–28 The May), the threeCaulle eruption major of volcano the events (4–7 Chilean of Puyehue-Cordón June),7 and 2011 the July). were eruption A the of characteristic eruptionsSO the feature of Eritrean of the Nabro volcano the2 (12 Grìmsvötn image June– eruption Fig. is 21).superimposed In that onto this the a SO figure, largedetected the amount by image of GOME-2 of corresponds theand respectively absorbing AAI to aerosols over 3.5. AAI index Aerosol has under detection been 2, on AAI the of north coast 2.5, of AAI Norway of is 3, not related to the start of the eruption.complementarities) The identified five many SO instruments usedmonitoring by of SACS (with the their Merapi’sthen space- southward). eruption and and time- its volcanic cloud (eastward movement and time, remote sensing (groundemissions deformation by spectroscopic by technique), apertureand together the radar, with ground and the deformation monitoring monitoring byvolcanic geodetic of of crisis, technique, the gas provided avoiding seismicity precursory the signalset death of al., this of 2012). several Explosiveof thousand and about people e living 0.44 Tg. aroundabout The (Surono 12 altitude km. of FigureAsh the 20 and SO presents SO SO to 28.6 DU for AIRS, on 6 May). of Java, Indonesia. Rapidcollapse ascent of the of lava magma domePeople put from had the the to large depths population move living away of around from the the their volcano volcano homes in and danger. around the the flanks of Merapi. For the first the second phase of emissions, a more significant amount of SO 5 5 25 20 10 15 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | -rich 2 cult detection of ash, c, was the eruption of ffi ffi ). We created a notification -rich plume associated with and ash in near real-time on 2 2 from satellite sensors is essential for 2 5962 5961 http://sacs.aeronomie.be detection and not the more di 2 erent volcanic cloud compositions (sometimes SO ff notification and dedicated webpage creation, an associated and ash are not exactly at the same locations. 2 2 and ash clouds took the same trajectory, nevertheless the high 2 c during the last 10 yr. We can see the uniqueness of each eruption. This c densities with an estimated rate of growth of about 2–5 % per year during ffi ffi MetOp-B), and possiblyoutcome also of the improved on-going SACS2 satellite project); data products for ash (as an to incorporate more sensors in the system (in particular IASI and GOME-2 on c, the increase of volcano surveillance is a critical need for future aircraft safety – ffi Finally, the next objectives for our service are: The near real-time monitoring of ash and SO In this section, we have shown the major volcanic events which have disturbed The last 2012 eruption which caused a disruption to air tra sun), more than 95 %actually of considers the only notifications thehowever have SO for been successful. each The SO image warning of system ash/aerosols isthe provided. observations of In ash particular, from a IASI and level AIRS of (Clarisse confidence et is al., 2013). included for have assessed the limitationsnotifications. At of the our time system444 of notifications writing, and (emails the estimated sent SACS the within multi-sensor information warning April success and system 2012. rate links generated With to of(mainly images) a the due since number its of to activation 17 observations false at notifications high provided by solar UV-visible zenith sensors angle or during an eclipse of the the international Volcanic Ashonboard Advisory polar Centres orbiting (VAACs). platforms,Service Focussing this (SACS). on This study free instruments service presents providesa the images global of Support scale SO via to asystem Aviation web interface Control and ( demonstratedduring that the it is lastsynergy able decade data to that products detect weresensors from all (AIRS a UV-visible volcanic and sensors threat IASI) events (OMI with to that a and aviation. revisiting occurred GOME-2) time The of and (at current thermal least) system 6 IR h uses anywhere on in Earth. We air tra the period 1990–2050 (ESCAP, 2005).tra With the increase of commercial(Prata, and 2009). freight air failure. Europe, North America, the north Atlantic and Asia regions have the highest Ash emitted from volcanoessucked poses into a the significant aircraft’s threat engines, to it aircraft readily because melts once and it can is potentially cause engine diversity is characterised by di and/or sometimes ash-rich) driven by todispersing specific the meteorological conditions plume occasionally over severalnotification continents. system To from synthetize 2010 the to full 2012,activity performance the diagnosis of is of our presented SACS in monitoring of the the Appendix volcanic A. 5 Conclusions and perspectives cloud was notthis particularly eruption, ash-rich. SO Weconcentrations can of SO see in Fig. 24 thatair for tra the first day of by SACS that were able toTokyo monitor VAAC the reported volcanic of cloud. The anDespite ash ash this, advisory cloud no board ash at from was the an detected altitude by of the 10 instruments km, usedthe spreading by Chilean to SACS. Copahue the volcano NNW. (23–25ash December). emissions An was spewed SO intoover the Chile sky and (Fig. aviation 24). authorities TheContrarily in volcanic to South plume America the was warned transported previous airlines eruption to of avoid the Puyehue area. in June 2011, the Copahue’s volcanic sent out an ash-cloud aviationin warning that and area were the cancelled. major Lessthe intercontinental than Tolbachik, routes two erupted months that on after pass this 27north eruption, November. a and The nearby northwest main volcano, (NNW), part asyear observed of and by the IASI for volcanic and this ejection AIRS location, drifted sensors. At the this thermal time IR of the instruments were the only instruments used Figs. 11 and 12). With a cloud rising to an altitude of about 10 km, the Tokyo VAAC 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ). The , 2008. and SACS2 projects) + ce), the Darwin VAAC ffi www.volcano.si.edu plume height from satellite 2 airs and the European Space Agency ff erent levels of notification, in line with ff 10.1080/01431160802168434 5964 5963 , 1999. c safety, all the strong eruptions with a threat to ffi ). Many thanks to ESA for the funding (SACS, SACS 10.1136/oem.59.8.523 http://vast.nilu.no ce for Scientific, Technical and Cultural A ffi to implement new visualisation toolsthe and di users needs. In particular, customised notifications will be set-up to trigger to operate athermal new IR instruments notification (Clarisse system et al., selective 2013); to for provide the detection informationobservations (e.g. of in Van Gent ash et NRT using al., 2013); on volcanic SO volcanic plume dispersionproject modelling ( and forecasts as part of the ESA VAST – – – 2005, Int. J. Remote Sens., 29, 6667–6685, doi: Nicholson, R. A., Norton,volcanic G., ash of Searl, the A.,1142–1145, Soufriere Sparks, doi: Hills R. Volcano, Montserrat: S. hazards J., implications, and Science, Vickers, 283, B. P.: Cristobalite in AIRS Algorithm Theoretical Basis BasisVersion Document, Level 2.2i, 1B, PartCalifornia, Jet 1: 10 Infrared November Spectrometer, Propulsion 2000. Laboratory, CaliforniaRevercomb, H., Institute Rosenkranz, P.W., Smith, of W. L.,AIRS/AMSU/HSB Staelin, technology, D. on H., Pasadena, Strow, L. theprocessing L., and systems, Aqua Susskind, IEEE J.: T. mission: Geosci. Remote, design, 41, 253–264, science 2003. objectives, data products, and Bluth, G. J. S. and Carn, S. A.: Exceptional sulfur degassing from Nyamuragira volcano, 1979– Baxter, P. J., Bonadonna, C., Dupree, R., Hards, V. L., Kohn, S. C., Murphy, M. D., Nichols, A., Aumann, H. H., Chahine, M. T., Gautier, C., Goldberg, M. D., Kalnay, E., McMillin, L. M., Aumann, H. H., Gregorich, D., Gaiser, S., Hagan, D., Pagano, T., Strow, L. L., and Ting, D.: References This work was also undertakenP. F. under Coheur the and L. auspices Clarisse of are thewith respectively O3M F.R.S.-FNRS. The Research SAF research Associate project in and of Belgium PostdoctoralFederal the Researcher was O EUMETSAT. funded by the(ESA-Prodex F.R.S.-FNRS, the arrangements Belgian C-4000103226). State FinancialConcertées” support (Communauté by Française the de Belgique) “Actions is de also Recherche acknowledged. Acknowledgements. and the support.CNES and We EUMETSAT arefree for access grateful data to to ofthe AIRS NASA IASI Toulouse data VAAC and and on(Bureau (Météo-France), GOME-2. EOSDIS. FMI of the We Meteorology), We for London the wouldthe thank the Montréal Anchorage VAAC like also VAAC VAAC (UK-MetO (Government very also (NOAA), JPL/NASA ofwhich to the fast Canada), brings for Wellington acknowledge and us delivery the VAAC all the energy (MetService), the of and team users motivation for from OMI, and their very helps useful us feedback, to continue and to improve our service. aviation have been detected.year These 2012, results the prove SACSfalse multi the notifications sensors quality (success system rate of of has our 96 issued %). system. 316 For notifications the with only 11 for which SACS has detectedfollowing: 37 volcanic % activity. in The 2010, detection 62of % scores in volcanic by 2011, activity SACS and are considered 71 %particles the by detected in GVP in 2012. the is Note atmosphere, not thatthe as only the SACS criteria seismic based point activity on of plays the view a emission and key of air role gas tra in and their survey. From Diagnosis of SACS from 2010 to 2012 For the period 2010–2012, we havevolcanic investigated eruptions. the We success have listed rate all ofsystem volcanic SACS eruptions in and detected detecting compared by the them SACSin warning to total), the according volcanoesresults to known can to the be be Globalthe active found Volcanism corresponding for in Programme SACS this Table regions. ( period 4, The (80 which volcanoes in gives red the correspond location to the of volcanoes the 80 volcanoes and Appendix A 5 5 25 20 15 10 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , , , , 2011. 10.1175/1520- 10.5194/acp-8-7723-2008 10.5194/amt-4-1705-2011 with IASI, the September 2007 10.1016/0377-0273(94)90038-8 10.1029/2011GL047402 2 , 2012. , 2009. , 2010. , 2013. , 1999. 5966 5965 , 2008. , 2009. , 2008. 10.5194/amt-5-581-2012 , last access: 13 January 2013, 2010. 10.1029/2010GL044828 10.5194/acp-9-6041-2009 10.5194/acp-13-2195-2013 ects on aircraft operations, in: Fire and Mud: Eruptions and Lahars of Mount ff 10.1016/j.jvolgeores.2008.01.029 10.1016/j.jvolgeores.2008.10.002 10.5194/acp-8-3881-2008 anti, M., Casadevall, T. 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H., Flemming, J., 5 5 20 15 25 10 30 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | -line ff vertical columnsvertical columns BIRAvertical columns NASA/KNMI/FMI DU DLRindex (and 2–3 columns) h DU (EU: 45’) ULB 2–3vertical h columns NILU DU K (DU) 1–2 h 1–2 h DU 1–2 h plume height BIRA km o 2 2 2 2 2 2 Absorbing aerosol index KNMIAbsorbing aerosol index KNMISO Absorbing aerosol index KNMI – 2–3 h – 2–3 h – 2–3 h (h) 5972 5971 Duration of monitoring ) (km) coverage products 60 96024 260080 96 1920 24 SO 12 SO 24 220015 SO 1650 12 SO 12 SO 2 × × × × × type time availability (km Pixel (max) Pixel (max) Pixel (max) Pixel (max) Pixel (max) Pixel (max) Pixel (max) Pixel (max) Geographical coverage of SACS monitoring for October 2012. List of data products available from SACS. Zone 1 h 2 h 3 h 4 h 6 h 8 h 12 h 24 h ABC 14.5 %D 15.9 %E (5) 18.8 %F (5) 24.7 %World (5) 31.3 % 28.8 31.6 % % (7) 72.5 % 31.2 % (8) (5) (8) 36.1 % (8) (5) 44.8 % (7) 50.1 % 42.5 50.6 % % (9) 94.8 % 46.0 % (10) (10) (5) 51.3 % (10) (6) 57.9 % 61.9 (8) % 62.3 % 55.0 % (11) 97.3 % (14) 59.0 (14) % (7) (14) 64.8 % 71.0 % (7) 72.5 % 72.8 % (9) (12) 98.8 % 75.0 (19) % (19) 78.5 (19) % (8) 84.9 90.3 % % 87.9 % (8) 88.1 % 100.0 % (10) (13) (22) 88.5 % (22) (22) 90.9 % 97.0 99.8 % (8) % 96.0 % 96.1 % (8) 100 (10) % (14) (30) (30) 98.0 % (30) 98.5 99.7 % % 100 % 99.4 (8) % 99.4 % (11) 100 (9) % (15) (38) (38) (38) 100 % 100 % 100 100 % % 100 % (13) 100 % (17) 100 (23) % (15) (71) (71) (71) (ENVISAT) (Aura) (MetOp-A) (MetOp-A)AIRS(Aqua) Infrared 09:30 p.m. 01:30 a.m. Sep 2002–present 15 01:30 p.m. Ash indicator Ash indicator ULB ULB – 1–2 h – 1–2 h SCIAMACHY UV/visible 10:00 a.m.OMI Apr 2004–2012GOME-2 30 UV/visible UV/visible 01:30 p.m.IASI 09:30 a.m. Sep 2004–present Jan 2007–present 13 40 Infrared 09:30 a.m. Oct 2007–present 12 Instruments Data Overpass Data Resolution Swath Global Data Participants Units Delay Table 2. Table 1. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 14 2010 Fukutoku-Okanoba 517 2010 NW Rota-1 − notification system. − 5974 5973 2 ) (m) notifications. ◦ 2.767.79 29628.425.53 748 2010 3726 Ol Doinyo Lengai 2010 1330 2010 Batu Tara 2010 Rinjani Langila 2 42.8321.23 1122 2632 2010 Chaitén 2010 Piton de la Fournaise 14.27 797 2010 Gaua − − − − − − − )( ◦ 77.37 1.22 4276 201072.65 Galeras 17.3319.05 64.42 63.63 1725 1512 2011 2011 Grímsvötn Katla 19.62 63.63 166684.7090.60 2010 10.46 Eyjafjallalökull 14.38 1670 2552 2010 2010 Arenal Pacaya 169.94 52.83 1730 2011 Cleveland − − − − − − − − 307 35.91 106 111111 160.64 160.32 56.06 55.13 4835 2376 2011 2011 Kliuchevskoi Kizimen 211303 141.49310310 24.28 311 123.58 311 116.57 404 148.42 408 167.50 101 106 55.71 111111111 156.02203 158.03203 50.68 153.93210 52.56210 1156 48.96211 1829 139.53 2010211 1170 123.68 2010 Ebeko 34.08 145.80 2010 Gorely 13.26 144.77 Ekarma 18.13 815 2462 14.60 2010 570 2010 Miyake-jima Mayon 2010 Pagan SACSregion Longitude Latitude106 Summit ( Year Volcano name List of the volcanoes having their last eruptions in years 2010, 2011 or 2012. The Key criteria used by the SACS SO 300 km) < InstrumentsThreshold radiusType of observationThreshold values SCIAMACHYThreshold value GOME-2 80 km VCDproximity volcano ( 1.8 DU OMI 1.25 DU 85 km VCD 1.8 DU IASI 1.45 DU 50 km 1.45 VCD DU 1.25 DU AIRS No need No 2.9 need K No need DBT No need 3 DU VCD Avoid SAAthreshold value Avoid pollutionthreshold value Yes 3.25 DU Yes 3.25 DU Yes 2 DU Yes 2 DU No Yes 1.6 need DU No need No need No need No need corresponding SACS regionaltitude of of these the volcanoes, summit)SACS their system are has presented. positions identified The an (latitude, red SO longitude band and corresponds the to the volcanoes for which Table 4. Table 3. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 5976 5975 ) (m) ◦ 2.001.47 5230 50231.52 20121.41 Sangay 2012 34700.38 Tungurahua 3058 2012 2891 Nyiragongo 20128.11 Nyamuragira 20126.10 Marapi 36766.14 813 2012 Semeru 2012 1750 Krakatau 2012 Bagana 37.8519.53 299716.25 36110.38 2012 1334 Copahue 2012 851 2012 Yasur Ambrym 2012 Tinakula 39.42 2847 2012 Villarrica − − − − − − − − ) (m) − − − − − ◦ 0.08 3562 20117.54 Reventador 7.94 29684.27 23294.08 20115.05 688 Merapi 2011 1807 Tengger Caldera 2011 2334 2011 Rabaul Manam 2011 Ulawun 40.5977.53 2236 3794 2011 2011 Puyehue-Cordon Caulle Erebus 35.24 4107 2011 Planchón-Peteroa 15.4019.75 1496 515 2011 Aoba 2011 Tofua − − − − − − − − − − − )( ◦ 71.17 90.8891.55 14.4798.62 14.7683.77 3763 19.0262.18 3772 10.02 2012 5426 16.72 Fuego 2012 3340 2012 Santa Maria 915 2012 Popocatépetl Turrialba 201275.32 Soufrière78.34 Hills 78.44 4.8976.03 5321 2.93 2012 Nevado del Ruiz 5364 2012 Nevado del Huila 71.93 )( − − − − − − − − − − − ◦ 84.23 10.20 2708 2012 Poás 72.12 87.0085.62 12.7086.85 11.54 1745 12.60 1610 2011 1061 San 2011 Cristóbal 77.66 2011 Concepción Telica 70.57 155.29103.62 19.42 19.51 1222 3850 2012 2012 Kilauea Colima 175.07 − − − − − − − − − − 412412 169.44 168.12 404 203 203 203 204 206206207 15.21210 15.00210 40.67 38.79303 130.66 37.73303 129.72 13.60 924 31.58 3330 29.64 2012307 613 2012 1117 Stromboli Etna 799 2012 2012 29.25 Erta Sakura-jima Ale 2012 Suwanose-jima SACSregion Longitude Latitude203 Summit ( Year Volcano name 303 303 307309310 29.20 310 100.47 310 127.63310 127.88310 112.92 1.49311 105.42 1.68404 124.79 1325 155.20 1335 2012 1.36 Ibu 2012 Dukono 1580 2012 Lokon-Empung 412 165.80 512 167.17 403 203 203 209210210 93.86210 130.86303 124.05 12.28 31.93 131.11 12.77 354 1700 32.88 1565 2011 2011 1592 Barren 2011 Kirishima Island Bulusan 2011 Aso SACSregion Longitude Latitude203 Summit ( Year Volcano name 307310310 41.70310 125.40310 124.73 13.37311 110.44 2.78311 112.95 1.11 2218311 152.20 1827311 2011 145.04 1784312 2011 Nabro 151.33 403 2011 Karangetang 167.83 [Api Siau] Soputan 111111111 161.36111 159.45201 56.65 160.59203 54.05 160.33203 3283 55.98 1536 55.83 2012 2882 2012 Shiveluch 3682 2012 Karymsky Bezymianny 2012 Tolbachik Continued. 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Figure Figure s are availab ), VAST ( resides resides and because we have no knowl SO , delays of retrievals, swath

SO 2 A (Munro et al., 2006 . Fig consulted - moving moving westward. This example shows and confirms that SO allow a good estimation a VCD is for all UV measurement the 19.42° (155.29°W; of Kilauea volcano The and str 2008 17 May in Hawaii, volcano of Kilauea andOMI eruption for an low) SO location of the plume between the 3 instruments. To the compare SO chosen for the 3 instruments, and the measurements have been plotted as a function of longit fairly good agreement between the VCD values is Figure Figure absorption absorption and scattering SO column emissions lower plumes. The SO influencing the UV light path in the atmosphere global data se as a function of longitude during an eruption of Kilauea volcano (155.29 Fig. 2. 18 May 2008. Fig. 1. right plot AIRS/Aqua AIRS/Aqua (Aumann et al., 2000

9 6 7 8 3 4 5 1 2 retrieval

18 19 20 14 15 16 17 10 11 12 13 the reliable and timely monitoring of volcanic plumes to define and demonstrate an optimal an optimal demonstrate and define to

2/MetOp - delivers delivers are

s shows the advantage of combining multip http://savaa.nilu.no

satellite satellite platform, data type and availability, data provider, units each instrument (resolution in km²) is an approximate value syste SACS the in used ash observations) It it allows the NRT SACS system also used data can still be satellite satellite instruments widely used to sound atmospheric applications: composition and GOME SACS data SACS measurements by space ( aim

9 7 8 5 6 4 3 2 1

19 18

16 17 14 15

11 12 13 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

1 - - 7 (see (see and and the time time by -

), 9 For For AIRS, cal cal column

. The AIRS gaps) gaps) and a .

1 1 to to 2760 cm - -

ne 2011 at the The The retrievals algorithm algorithm 1

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with with OMI during the 2 2 (

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emitted emitted by the Earth SO st ded in near real

IASI IASI SO

21 ieval ieval scheme of AIRS is a low low altitude

and and 14 from from 645 cm

the the The provi ed by a relatively good 5 km depending on the th

. - s (at nadir) ) cd cd the displacement of the

4 are .

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2 OMI during the OMIGr during GOME-2 and - monitoring monitoring of

d) is present at altitudes L1 L1 d s

), while the IASI algorithm is based on the after the

2 (c)

1 emissions. emissions. As most of the SO . retrievals retrievals are also affected by clouds and -

, and a second step to adjust the amount of

2 2 on GOME

2 and 2 and allow - absorption absorption band around 1362 cm cm

ed

2 and and a spectral sampling of 0.25 cm is We can see in but in the context of aviation it is actually an h olcanic plumes 28

, s from SO ws4.ulb.ac.be/Alerts

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1 ading over time. over time. ading (apodised) - of the outgoing thermal radiation 5980 5979 of

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- http://cpm both cm

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in detecting v in detecting sensitive sensitive to anthropogenic and AAI from from AAI and

AIRS and AAI from 327 and and 1385 cm images images from IASI and AIRS for the 13 UTC UTC

1 ULB ( 1 is limited to the atmospheric layers above 3 - rmal IR sensors (IASI and AIRS) (IASI and IR sensors rmal spectrum spectrum ,

(b)

asymmetric asymmetric stretch 1 2 -  the cm  IASB IASB using the algorithm from NILU. The retr

by these two sensors means that SO s there. As a general comment, SO -

 down down to the surface. cm 2 table and EUMETSAT operational pressure, temperature and humidity 2

density density

-

2 and b) AIRS b) and

e the to SO operate during operate

up 137 SO - 395

, days (ash detected by AAI retrieval by AAI detected (ash days IASI . The instruments are operating in a nadir view with typical footprints (circular to (circular footprints with typical view nadir in a . are operating The instruments 1

- can strong 1 (1 resolution resolution of 0.5 cm -

for IASI and a)

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the of satellite products products of satellite

8

(a) 2 rofile. rofile. This limitation might seem serious from from

- the next 2 next the 140 spectral spectral

0.5 vertical column density images from IASI and AIRS for the 13 and 14 June vertical vertical column

(and hence (and hence 2 2

line line radiative transfer calculations (see details in Prata and Bernardo, 2007). products of IASI and AIRS -

Ash index Ash 2

round : images and evolves as the instrument is degr the instrument as and evolves images are provided are provided in NRT by imitations with with a

4 Iceland. Images show the first days first of the show eruption the Iceland. Images 2 most most of their travel time. This fact combined w 2 Both sensors L

on system 5 index retrievals from the retrievals from index

SACS SACS SO b shows the IASI ash detection at 10:30 depending depending on the position on the swath) 2

Figure Figure

be tuned to avoid false instrumental noise (especially at high solar zenith angles for the UV sensors). The latter generally shows up in the SO 3. 3.5.1 SO Because of competing water vapour absorption sensitivity humidity vertical p advantage as the detection of SO spend component of the SACS system. As a complement, the measurement UV sensitivity sensors are characteri degassing, it also renders the measurements hotspots are confined to a limited number of regions (China, South Africa, Siberia), the SACS system can easily 4 during ash cloud resolution of resolution :

3 SACS SO Ash index from wavenumbers wavenumbers are used IASI SO SO

based based on off

retrievals retrievals are processed by BIRA step step process with a first step to identify pixels tical

- 3 4 5 6 7 8 9 1 2 2 2 10 11 12 13 14 15 16 17 hree Both IR instruments cover t measurements a NASA's Earth Observing System Data and Information System (EOSDIS, SO two SO from details in Clarisse et al., 2012) also involves the conversion of the measured signal into a by making use of a large look Figure Figure beginning of the eruption of Nabro. Note that IASI 15 km and km. 12 diameters respectively of and AIRS observations are plotted using circles with mean ellip respectively. atmosphere 3.2 3.2 The IASI instrument is a Fourier transform spectrometer. The spectral coverage is (with no gaps) instrument is an echelle grating spectrometer covering th spectral Fig. 4. Grímsvötn eruption on Iceland. Imagesafternoon show the of first 21 days May of 2011. the eruption, which started on the Fig. 3. 2011 at theplotted beginning using of circles with the mean eruption diameters of of respectively Nabro. 12 km Note and 15 that km. IASI and AIRS observations are

9 6 7 8 1 2 3 4 5 12 13 14 15 16 17 18 10 11 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

, 11

Table Table

the IR is is in in

VCD from 10 2 has ible see than than 2

arth's vis E sh) sh) and - n December

, because in in the region Thanks Thanks to its

. ionosphere ionosphere (at ess OMI on 2 January . ons). ons). This dip in ab from from UV 2, IASI, AIRS). The the ash of product the ash -

5 are are not treated

. (c) y y the SACS system; and he he row anomaly exist Fig For For example i emissions emissions and the strategy rows

2 affected affected by the SAA Note that Note

2 January 2008 . As a result of this, the inner result a . As of the this, inner nitoring nitoring system. Because of the lower lower into the less less A, pass daily through the inner on - measurements r October 2012 October r visible in is

2 instruments induced by the South - , , as is penetrate penetrate every every 2 hours 50% of the time ( , OMI

GOME-2, and and and MetOp

vis Neverthel instruments). detection detection alone). processing. e.g.

- - t should be noted that because of the strict 2 2, 2, and c) OMI plume is related to the eruption of the (b) - artefacts 8 h of monitoring from SACS instruments line schemes to correct for t 2 - , Aura ). Currently, the affected from axisfrom rotational the

noise (b) other other sensors in in a 24 hours interval. The percentage value drops to emissions

sampled sampled depends depends on the day of year.

. nvisat affected.

called called "row anomaly" since 25 June 2007. This anomaly with - lts lts in of SACS monitoring fo monitoring SACS of the the combined detection of both elevated aerosol and SO he South Atlantic Anomaly (SAA) and it covers a part of hours of monitoring from SACS instruments (example of the SACS monitoringof from hours

5982 5981

e e.g. the coverage of the Earth by SACS after 8 hours of

Several Several off SCIAMACHY SCIAMACHY and GOME latitude latitude regions due to overlapping orbits. This is particularly energy energy charged particles) is on one side closer to the global global monitoring system of SO

- ). - .

of October 2012). of October is lessis c F zones th - and ash

E 27 SCIAMACHY, 2 - OMI

; coverage VCD VCD from SO concentrations

(a)

ellites, ellites, such as E 2 of D 2 the SACS in Table 2; b) 8 Table in

retrievals retrievals and resu

is the percentage of the region of interest sampled b 2

plume plume is related to the eruption of the Llaima volcano (Chile), marked by a blue sampling used

in the data coverage

ected. 2 field aboutis offsetfield km by 500 pxl

ff irection irection angles, corresponding to rows on the CCD detector. The row anomaly tional SO tional orbiting sat volcanic region. region. Upon passing the inner belt, charged particles may impact on the detector, shaped shaped regions of high - www.knmi.nl/omi/research/product 2 (as can be seen Fig 5 Fig seen be can 2 (as - VCD VCD from a) SCIAMACHY, b) GOME - outhern outhern Atlantic Ocean: it lies roughly between latitudes 5°S and 40°S, and between -

tial etic 2 S s yields very few false detections. But i

VCD from better better protection to radiation than side. This region is named t less less good (due to the SZA limit for UV : Geographical Geographical :

but are not implemented yet in the NRT data NRT the in yet not implemented but are excep 2 2 visible on these images on visible ected by the SAA. The SO . Low )

normal normal radiance values, which in turn decreases the quality of the measurements, notably in

. The SO - magn ff

of time time any location in the world GOME %, 60%, 50% and 30% for periods respectively of 12, 8, 6, 4, 3, 2 and 1 hour(s). 2 and 3, 12, 8, 6, 4, of respectively periods for 30% and 50% 60%, %,

are - esent esent results from time time (see or than n the SAA

- Table Table and spa g to a reduction

geographical geographical coverage the higher sampling rates for high users users

been evaluated: e

f Iceland is Example Example of SO hich hich gives it s

orbiting orbiting satellites with different overpass times, some geographical regions are observed more : d over than than the other are are sensitive to all types of absorbing aerosols (desert dust, biomass burning aerosols, volcanic a - leadin w

5

a) Geographical zones zones Geographical a) , arth's dipolar arth's and and AIRS sensor Known anomalies impacting the data the impacting anomalies Known Aerosol products Aerosol

arth's arth's magnetic field allows charged particles and cosmic rays to nes (see Fig. 6a) and we have estimated, based on data of October 2012, the percentage of the areas Yan et al., 2012 al., et Yan

OMI instrument has started to suffer from a so : E E 3 2 Geographical zones used in Table 2; 6 to warn to zo e

emporal e.g. e.g. Figure Figure affected by the SAA triangle in the plots. Artefacts in the SO Anomaly Atlantic Th affects particular viewing d increase SACS ( ~500 km of altitude) radiation belt i causing higher the UV. The SAA affects the SO design SCIAMACHY 3.5. Besides the fact that the aerosol products are qualitative products (indexes), sensors are therefore not purely selective for ash. However, than (in SO even plume fact more for the volcanic highly selective IASI implementation. current in the detected not are often plumes ash concentration 2, low ofstep conditions 3.5. The Van Allen belt (doughnut surface South America and the longitudes 0°W and 80°W (the precise strength, shape and size of the SAA varies with the seas the apparent apparent is is the maximum number of overpasses. From Table 2, it can be seen that with four instruments, SACS T Example of SO

Note Note that th Global monitoring Global of

1 Figure Figure lso

. 3 4 5 6 7 8 9 1 2 2). the coverage o A interesting for Icelandic volcanoes (zone E) that will be monitoring monitoring in Fig. 6b). Table 2 presents the results for the different parameters zones ha and time durations. A set of two max monitors in near real 75 90%, 95%, 99.5%, 4 In this section we pr adopted 4 It is important to know precisely the time and space sampling of the SACS mo use of polar frequently than others. To evaluate the revisiting frequency of latitude SACS, we have defined seven geographical that have been observed at least once by one of the satellite instruments (OMI, calculation GOME was done for several time intervals (se 23 24 25 26 18 19 20 21 22 10 11 12 13 14 15 16 17

(example of 27 October 2012). Fig. 6. (a) Fig. 5. 2008 in theLlaima region volcano (Chile), a markedSCIAMACHY by and a GOME-2 blue instruments trianglethese induced in images; by the OMI the plots. is South Artefacts less Atlantic a in Anomaly the are SO visible on 8 9 5 6 7 1 2 3 4 16 17 18 19 14 15 10 11 12 13 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

-

2 2 . . 2 13 - 14 ather ather more more

region special special

at ). To avoid represents same same 3

. from GOME from For IASI, r to users as soon 3.5.

in in the below

. Finally, one

potentially potentially multiple ) ); b) locations of SO b) locations );

vertical column density 2 are system system considers lower again

emissions. emissions. To avoid false

The black ellipse ellipse black The notification

2 SO . a , or pollution.

s (see Table 3 Table (see

notification (a) IASI IASI and AIRS, and they produce warnings pixels. SAA is detected (see Table 3). Note also th in that the

. An illustration of the SACS multi 2

vertical column density vertical column density system. less less than 300 km the system

2 SACS

), ), and is therefore straightforward. The ] SO ces plume est est China, Central North Russia and South

the the K . SACS send a) a) . warning respectively respectively

. (distan

notification

elvin elvin [ K 12 hours, a pixels

ific ific areas (W SACS of

locations of SO the 5984 5983 of December 2012 December of from from the South Atlantic Anomaly (see section

warnings

(b) rd s hreshold hreshold value is considered t a period The different parts are described in more detail more in described parts are different The

. monitoring service. monitoring

8 2

small small eruptions and degassing, affected by instrumental noise,affected by instrumental come the 23 the

Overview of Overview

within : defined defined geographical regions Fig. - 8 observations observations (from one of the instruments), the first step is the analysis of he SO

close close to a given volcano in . If 2 s that they are sensitive to anthropogenic SO adius” considered in the SACS in the SACS considered adius” more more strict i used used are given in Table 3 for s r volcano

(to avoid sending redundant information)

for t for Predefined Predefined world regions used by

SO s

Figure Figure : or not at all 9 ible sensors

plumes plumes from new new s. s.

(called (called DBT and expressed in vis sensor 2 relies relies on pre -

hreshold hreshold is detected

Copahue t

s dedicated region dedicated SO

Figure system and

is generated

much much less strict strict criteria are used for some spec sensor warning system warning sensor in in this region, a visible plume - threshold threshold values based on VCD, the criteria apply directly on the measured Difference of

from thermal IR sensors thermal from for a for - for measurement

(DBT and VCD)

s system is presented is presented system

notification more more , s ruption of the ruption of the values values E for two pixels above the “threshold value” is shown with the issues warning the with of issues is value” shown twopixels “threshold above the for volcanic volcanic using the criteria defined in section 4.2.1. After a volcanic eruption, there warning warning service

: warning

2 7 SACS multi SACS notification notification notification

SO new new

zoom zoom 2 new new notification

2 2 . 2 A . the area defined by “ defined the the area hreshold hreshold Figure Figure

IASI IASI and AIRS are than considering Brightness Temperature threshold values no false almost Another Another limitation of UV false settings are used for t limitation of UV notification Africa). SO

As soon as SACS harvests the data The as a no sensors SO 4 Eruption of the Copahue volcano 23 December 2012. Overview of the SACS notification system.

8 9 4 5 6 7 2 3 1 8 9 1 2 3 4 5 6 7 10 11 12 13 14 15 Fig. 8. from GOME-2. A zoomwarning. for The two black pixels ellipse above representsthe the the SACS “threshold warning area system value” defined (see is by Table the shown 3); “threshold with radius” the considered issues in of Fig. 7.

- 14 region Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | same same

2 2 .

s to users as soon d

15

time time in in the noise - below signal

potentially potentially multiple

2

the SO e shown in notification are d, the related d, the related again for this region for region this

is issued. This

issue notification many many is

a

o

s notification concentration detected. concentration notification

notification 2 is detected are are used in the near real

SO

. An illustration of the SACS multi s notification going going system.

-

SACS shows shows the locations (and associated plume

region region number, some details about the oordinates of the maximum 9 the the . SACS send , c the Figure Figure

notification decided decided to consider a set of world regions of 30°

email email notification (see also the exampl s less than 8 hours, the visible sensor depending on the day of the year. The the system - te te that the same region 12 hours, a The

a flag indicating whether a cloud correction has been sers sers and also to avoid issuing to

SACS SACS , status status can possibly become ON. The system compares the ).

of 5986 5985 in latitude.

it it has been

and ash images. As soon as a As soon images. ash and

the the 2 each UV

and and the instrument, 75° gathered into a notification sent by email to subscribe who users sent by email a notification into gathered

SO sent to users in case exceptional of to case an in users sent

warning is

status” status” of this region. If there is no on a period

The different parts are described in more detail more in described partsare different The

SACS SACS system. No

. monitoring service. monitoring is used for

8 warning 2

the

notification notification off - polewards polewards of Overview of Overview warning

“ of observations (UTC) within : Fig. Fig. defined defined geographical regions cut - 8

email email observations observations (from one of the instruments), the first step is the analysis of he SO per region and per 12 hours). per and region per

in

the solar zenith angle. solar zenith the . If 2 since since 12 hours), the

(to avoid sending redundant information) status for t for vide timely information to the u

Predefined Predefined world regions used by

SO

. Figure Figure on related to the

the time of the : : 9 ted ted by the system. For this reason, notification

and finally and finally new new Example of an of Example an

warning notification : specific) relies relies on pre solar solar zenith angle - is detected http://sacs.aeronomie.be/alert/subscribe.php 10

otification dedicated region dedicated Example of an email notification sent to users in case of an exceptional SO n

Figure system and Predefined world regions used by the SACS notification system and for the SO is generated essing, essing, a link to a dedicated web page generated by Figure Figure

up enables to pro - sensor warning system warning sensor mail mail plume - - for a for (instrument Note that a values have been determined empirically to have the best coverage while limiting the increase in set one (maximum E informati Important to SACS ( Fig. 10) contains proc along with the date and time not, or applied warnings warnings genera by 30° plus two polar regions name/number) of the 62 regions of the to display services archive and monitoring ‘ON’. is flagged region of the Check The second step is to check the (meaning no time of observations with the processing time. If the delay i

system is presented is presented system

Fig. 10. concentration detected. Fig. 9. monitoring service.

7 8 9 4 5 6 1 2 3 20 21 22 19 18 13 14 15 16 17 10 11 12 using using the criteria defined in section 4.2.1. After a volcanic eruption, there volcanic volcanic warning warning service

warning 2 SACS multi SACS notification

SO new new

2 new new notification 2 . 2 . the data As soon as SACS harvests SO The as a no sensors 4

8 9 6 7 4 5 3 2 1 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

2 - 16 Fig. Fig. SO

the the

oogle 17 s a G

) and brightness brightness nk to the 2

1 2 . warnings

notification side. side. Below the Fig. e the images IASI - , , and a s 2, which took Note Note that our historical historical data (eruption of (eruption -

by this by

- (see , SZA, maximum page shows a box with

page is given with all after after For a given region, a

112

years years of

a given month/year and ber 2012 ber as there already wa The

ours notification h nine ser ser can visuali friendly friendly way. , for - u in addition in to addition the SO n the SACS portal, allows any ten ten Septem

,

. the warning st the the region ) terest

about about each of them) is also provided and and

of

as explained above. The map of the of in

, the ,1 the and and aerosols/ash side two point, point, the )

(see (see next section). 2

for a specific notification is shown in available available o http://gmt.soest.hawaii.edu

, notification SO and and ash in

location year year (from 2004 to 2012), an image of all the time time monitoring web

see see - warnings, warnings, Kuril islands Kuril warning warning 2 data archives archives are automatically updated on the SACS

web page visible instruments, there is also a li -

warnings

instruments - each signal A passed over this area.

This tool ber 2012. Confirmation of Confirmation 2012. ber -

2 service. This section presents an overview of all the ing different mapping tools (interpolated image using (interpolated mapping tools different ing

VCD image. As a complement, a map showing the the

2 SO

warning vents. vents. Septem SO 5988 5987 select select 1 warning archive

(notification to on

2 , corresponding corresponding s he relevant links to the different webpages. different to the links relevant he - . For the UV ) ser k to the u IASI

system, system, the oving the cursor on a

image. image. In case of a IASI (time (time of measurement,

. . No notification has been sent to the users, all all the

system system is only operational since April 2012,

a lin

10

a listing including more information instruments), instruments), and a link to the data (files or link to data providers), for the

notifications (CCF) page Fig. Fig.

11, IASI also detected also When When m but the dedicated web page has been updated automatically with the notification rmations from AIRS and IASI took place. took AIRS and IASI from rmations Bezymianny volcano in the in volcano Bezymianny

all . In addition to this interactive tool, a common list with all the separates the time between two images from images from 2, - Fig. web sh notification notification

using using the same displaying template. Note that

generated generated by SACS using GOME archive

. In fact the processing of IASI was just 3 minutes after the one of GOME warning there is subpage subpage allows the is detected by the notification

and a and

ion’s ion’s

2 2 email email sensor with the location of

- of data and of data

SO : SO : warning

12 warning warning 2 2, two others confi others 2, two

is is shown with a highlight of the main e identified by SACS using the five sensors. For and aerosol images from GOME from images aerosol and - http://www.google.com/earth

a map notificat a web page IASI warning 2 s

years

SO

e is an interactive map. 2 The s

. the Figure Figure and ash images from IASI, on 1 September 2012. Confirmation of notification by and aerosol images from GOME-2 (notification web page), on 1 September 2012 : SO gs SO as a confirmation , see been been reanalysed for the development of the

2 2

11 Nine ed visuali SO SO Although Although the multi have notification notifications interested person to investigate historical eruptive emissions in a quick and user notification. a lead to always not might which eruptions volcanic of small monitoring the also allows system Update of Update As soon as a web site to minimum delay of 12 hours warnin corresponding to the with t available is also sorted) (chronologically 4.3 For For the example shown in act place at 23:42 UTC, as show notification based on GOME box for GOME from Confirmation of Confirmation image, one can find butlinks image, image two us to the same

This notification This notification was to sent the users 1h01 after MetOp 2 . Figure Figure

Earth file cloud corresponding cover fraction temperature index image volcanoes in the region (with a link to on this web page. Furthermore, a direct link corresponding SACS to images (for the near real considered. region An example of 11 the information of the value, and the use of cloud data in calculations), and the images of SO the Generic Mapping Tools from the University from Hawaii, Dedicated Dedicated 2 3 4 5 6 7 8 9 1 16 17 18 19 20 21 22 10 11 12 13 14 15

2 3 4 5 6 7 8 9 1 Fig. 12. (eruption of the Bezymianny volcano in the Kuril islands). Fig. 11. IASI. 10 11 12 13 14 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

, 3 of

19 The The km (see (see best best

9.50 9.50 × 2) derland derland week

as can be ;

s s the At the end

. up to stratosphere. stratosphere. wa

ash ash density of he he bor

er Iwojima Iwojima (about T

n -

. Details Details about the he main volcanic of November 18 the the first a

ejected ejected in the low

T

3 . of the Sierra Negra th volume volume of 0.15 ng a

volcanoes, volcanoes, including a 27 the archipelago of the was

This eruption emitted a , uring uring eling eling westward . Fig. 1 eight eight of Minami

. . D . Assumi he submarine eruption of the kg and

gives gives an emission T has continued in 2005 11 1) km km long curtain of lava fountains

- 5 can be found in Bluth and Carn or this period. f in 2004 mal mal IR sensor (AIRS)

. containing r the night of the

le le s into into Iceland

1) On 6 October, a eruption large explosive

also also visible: monitor the volcanic plume volcanic the monitor began began in

) in the Andes Cordillera (Colombia and Peru) . Volcanic . Volcanic ash from the eruption fell as far away , 2005, and 2006 and 2005, , c

to . 3 are 1 Witham Witham et al. (2007)

, s for 2004 s for Fig. Fig. Galapagos Galapagos and Vanuatu ceased Sierra Sierra Negra volcano, Galápagos, Ecuador. After 26 years an an erupted mass of 3.3 × 10 5990 5989 Hills volcano from 20 May to 8 June 2006 (from right to left). to right (from June 2006 to May 8 20 from Hills volcano eruptions eruptions

instruments instruments are availab and and in notification

notifications notifications over Europe

A strong eruption 2 her her parts of the world: . SACS this this time of the year, the the uption, uption, a huge amount of gas and particles : SO

Soufrière the the Independent State of Papua New Guinea 13 by by SACS showing the volcanic cloud trav from from the VAACs

is is one of the most active region tic tic Republic of Congo (DRC), as shown in of this volcano volcano of this

n

s term term disruption of airline traffic - Figure Figure , and AIRS issued of two additional in in Iceland volcano) (Grìmsvötn o several 2) the eruption of the

OMI

emitted by s and and ash reached an altitude estimated below 5 km (Yang et al., 2009) Democra

active active in 2006

emitted by Soufrière Hills volcano from 20 May to 8 June 2006

, that corresponds to Note Note that at ; 2 , 2 from 2004 to 2006 (SCIAMACHY, OMI, and AIRS) and OMI, (SCIAMACHY, to 2006 2004 from

. 2 emissions emissions from Nyiamuragira from 1979 to 200 and and Uganda in 2004 is i

also also 2 Tokyo) have been was , and the

During During this effusive er presents presents als of s Notifications Okanoba Okanoba volcano, located 6 km northeast of the pyramidal island

six months after an earthquake on an active fault, the volcanic activity he signature - a images of imagesSO of T

est est 3

.

4.3.1 SCIAMACHY w b - eruption eruption occurred

3

h release period 1 OMI and using dispersion models

- 2 1 the : (best coverage and time laps between observations) laps between observations) time and coverage (best 3 for for the larger plume - outh

s 1 14 - m notification monitoring monitoring of SO Figure Figure 1 . Fig. Fig. gain on 22 October 2005 with a fissure opening inside the rim of the caldera

hr . g

the three strongest eruptions in occurred ot 12 Figure Figure ata ata from ver ver the 35 OMI images of SO SACS notifications for 2004, 2005, and 2006. In 2006, volcanic activity has been detected by SACS ( but took place at Rabaul volcano (Papua New Guinea), sending a plume of gas and ash up to the low Several Nyamuragira volcano Japanese Japanese Fukutoku 1300 km being inactive and raised a volcanic cloud with an estimated volume of 150 millions m³ of gas with a 2 (Geist et al., 2008). troposphere. The plume of SO emission atmospheric 2005, of October D activity detected by SACS Republic of Vanuatu between Rwanda, the DRC Mount Nyamuragira and Mount Nyiragongo which were both erupting on May satellite 25, 2004. (2008). November, an as mainland Europe and caused short 2200 kg 10 o instrument The volcanic in activity DRC (Galle et al., 2005) seen in

2 3 4 5 6 7 8 9 1 24 25 26 27 28 29 16 17 18 19 20 21 22 23 10 11 12 13 14 15 Fig. 14. (from right to left). Fig. 13. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 10 (a)

a

a). a). 22 6 few days days few a that

b 5

21 1 Fig. in on a) 10 August 2008; b) 11 2008; August b) 11 on a) 10 1 August that the detected ash

. We can see We can see 10 and 11 August (interpolation with

on 3 November. This volcano, located in the on IASI IASI We can see on 1

7, 2008, and 2009 and 2008, 7,

Ale Range. Ale Range. . 200

s for clouds clouds show a similar pattern on 10 August (see Fig. 1

2 5992 5991 emitted by the Kasatochi emitted by volcano August 2008 August

notification as as observed by SACS

: 15 Kasatochi Kasatochi

Figure Figure and ash index index ash and level level of confidence over the south of Alaska and the west of Canada is an

from (up to 676.4 DU on 8 August).

eruption, eruption, Dalaffilla volcano erupted cloud (see Fig. 16b). (see Fig. cloud

2 images. images. The ash and SO

cloud cloud

2 2 The The ash images from IASI (showing the level of confidence of the detection) have been O . S column density column

rich cloud 2 - 2 the SO the the Kasatochi

SO

column density and ash index emitted by the Kasatochi volcano on over

after after IASI 1 11 August 2008.

2 : s presents presents 16

6 posed (b) 1

im ure Figure Figure IASI SO Fig grid of 0.25° by 0.25°) super Note that ash observed with a low artefact in the analysis of the spectrum and Kasatoshi was the a SO process of ash detection. The volcanic plume SO the than cloud is smaller emitted by Two month in the Erta volcanoes ofsix is one the Ethiopia, of Afar region SACS notifications for 2007, 2008, and 2009.

2 3 4 5 6 7 8 9 1 10 Fig. 16. Fig. 15. August 2008; Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 16 (a)

2 s th he for for 23 and and T wa

. me me June, June, SO

): ): Redoubt plu (ash image

th

c 2 5 7 s s detected by 16 1 1

Kuril Kuril islands

Fig. Fig. 24 Fig. Fig. of the atmosphere ( two days before

the into the atmosphere

No ash wa 2 . budget on a) 16 June 17 June 2009; on a) b) 16 the volcanic cloud generated shown shown in

as emitted are (UTC (UTC time) of the w low level of confidence) over the

volcano

observed observed on the afternoon of the 17

AIRS plume plume

with with a

2 morning cloud

Sarychev Sarychev volcano in SO 2 Sarychev the the first

10, 2011, and 2012 and 2011, 10, , and . On detection detection (

observed observed by

s s for 20 s for n 2009. er the Sakhalin Russian Island islands

.

loud ov emitted by the emitted 5994 5993 b shows the SO June identified identified by the SACS warning service

emitted a emitted huge of amount ash SO and 7

Note Note that the 1 ) that the ash is an artefact

significantly significantly affected the radiative .

a) were SACS notificatio SACS ure

see 7 : and ash c Galápagos 18 2 Fig

2009 2009 SO

Figure Figure y and ash index index ash y and 9 2009 June We can 1 . - (see Fig. 1

(Carn and Lopez, 2011; Clarisse et al., 2012). The mass of the SO of the 11

( s

image) . occurred occurred in

2 located 16 km mage - - I column column densit

. co that 2 s s in the last 50 years, ± 0.2 Tg by Haywood et al. (2010). This eruption, which was one of the 10 largest over India and the south of China south and the India over

SO of 10 the SO

s which which was the largest observed in Ethiopia in historical times,

s well well 1.2

column density and ash index emitted by the Sarychev volcano on over AIRS 2

be : 17 17 June 2009. eruption of eruption Sarychev eruption,

notification posed

. The ash cloud detected by AIRS is located 2 major major eruptions over the Pacific ocean Pacific the over

im (b) observed observed on the West coast of USA. Figure Figure

SO June

Haywood Haywood et al., 2010) AIRS SO SACS notifications for 2010, 2011, and 2012

estimated estimated to stratospheric injection ( super Russian land on the north of the Sea of Okhotsk and ash cloud are was of AIRS Three volcano in Alaska, Fernandina volcano in explosive a range of altitude six after this

3 4 5 6 7 8 9 1 2 11 12 13 14 15 16 10 Fig. 18. Fig. 17. June 2009;

, - .6 of 10 26 . . In 2 Rapid Rapid SO . unusual unusual presents presents . For the

and and time during during Additional Additional

Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | affected affected by (up to 28 20

-

were Indonesia a mass of monitoring monitoring of the Figure

by IASI

large population living living population large was was measured the a good

2 (with (with their space the flanks of Merapi sulfides sulfides or sulphuric acid

put

SO

respectively about 12 km. 25

enormous enormous disruption to air traffic

be around 2010. Many regions satellites satellites was low (less than 5 DU)

creating n the Island of Java, Eyjafjallajökull Eyjafjallajökull o and and allowed the Merapi’s eruption (5 November 2010). (5 November eruption the Merapi’s

southward). year year causing monitored

a) ruption of ruption of , homes nd IR 8 used used by SACS the e in Iceland were relatively small, but

ant ant amount of the the

20 April, ash covered large areas of northern during were during

.

for to to s estimated to 2

IASI) 4 3 November visible a signific -

volcano in spring 2010 image from IASI during the Merapi’s eruption

(AIRS and (AIRS

f the seismicity and the ground deformation by geodetic over over Europe (see (see Fig. 1 2 SACS and and water vapour

UV

from IASI IASI from s s 2

5996 5995 sensors From From 1 IR

away from their . volcano (Iceland) Ash Ash and SO

ich ich plume wa and the collapse of the lava dome dome of the lava the collapse and r image Merapi Merapi on

- 2 he five instruments from thermal from

with images of the level of confidence of ash detection from AIRS from of of ash confidence level ofdetection with images the

T 9 SO mages . i monitoring monitoring o 1

identified identified by notification anymore

observed observed by index index 2

the and and ash

the 2 Ash

of Eyjafjallajökull : Fig. Fig. - November.

19 2 SO

s the one of ). ). Most of the airports of Northern Europe were closed by the authorities. olcanic olcanic ash cloud SO over v Figure Figure (see of the volcano of the volcano

on 5

many many 1 notifications posed posed . People had to move pted

2 im depths together together with rt of the eruption

SO s brought . the Ash index images from thermal IR sensors (AIRS and IASI) during the eruption of Ash image superimposed over the SO precursory precursory signals of this volcanic crisis, avoiding the death of several thousand people identified identified

he second phase of emissions, a more and its volcanic cloud (eastward movement and then and then movement (eastward cloud volcanic its and all all the The 2010 eruption

The altitude of the SO

Fig. 20. (5 November 2010). Fig. 19. Eyjafjallajökull volcano (Iceland) in spring 2010. on the glacier did not melt shows Ash image Ash super provided

a : e volcano in danger 8 th 20 1

falling falling and and ash measured by IASI

2 Figure Figure

and 15 days after the sta complementarities) eruption Merapi’s technique, living around (Surono et al., 2012). Explosive and effusive phases took place and released about 0.44 Tg. SO ascent of magma from from ascent of magma around first time, remote sensing (ground deformation spectroscopic technique), by aperture radar, and monitoring of gas emissions by possibly possibly due to local chemical reactions between SO May 2010, during t on 6 May) AIRS, DU for The strongest eruption of 2010 was localised localised disruption continued into May 2010. The eruption was declared officially over in October 2010, when snow eru volcano whenEurope the and IASI from 14 April to 17 April During these days, the quantity of Figure volcanic activity. meteorological condition across western and northern Europe over an initial period of six days in April 2010 (Zehner, 2010).

9 6 7 8 4 5 2 3 1 25

23 24 21 22

19 20 17 18

15 16 13 14

11 12 10

e 27 . Th erosol ) Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | b (12 (12 June 8 . A

1 3.5

). Fig. 1 of aerosols/ash (

volcano

201

2 y he he 28 level SO cloud, cloud, which travelled AAI over AAI h

able to Ma was ejected northwards was ejected northwards

2 the

southern southern 2 28 May), the eruption of - and and the the

that occurred that occurred

, the image of absorbing , image the the , SO , 3 2011).

Within Within a few day, t June

. the nine years )

, 6 2

2 AAI AAI of The The volcanic cloud emitted were the only sensors the only sensors were Fig. Fig. Out of the air traffic of

In In figure this and and ash clouds were collocated. 2.5, 2.5,

eruption 2 .

) (see (see

1 SO 2 Grìmsvötn eruption, 23 Grìmsvötn disturbed ( occurred occurred during the year 2011

2 AAI ofAAI - observed observed by IR sensors respectively during 3 Fig. Fig.

Grìmsvötn Grìmsvötn eruption. The SO Note that for this particular eruption Cordón Caulle Cordón - . the the consequently rich recorded by our system.

- 2 image ption is that a large amount of a amount is that ption large - 5998 5997 Puyehue image. image. A null, low, medium and hig (

t ash 2 Cordón Cordón Caulle volcano started. high high latitudes - June), June), and the eruption of the Eritrean Nabro

IASI and ash clouds were 7

2 - of the Icelandic Grìmsvötn volcano (21 by Puyehue s Puyehue see GOME see The SO to to the SO he first two days of this eruption, the the dispersed dispersed and circled around the South pole on sh emitted a of the SACS system to date and ash detected by ash and

During t the UV sensors had limited coverage and IASI and AIRS and IASI and coverage UVlimited had sensors the

, , this eruption is the mos 2 cloud cloud the eruption SO posed

the main the partmain of Southern :

plume. plume. 22 im

volcanic The volcanic the volcanic plume. and aerosols (ash) detected by GOME detected by (ash) aerosols and covered

laden archives archives span Figure Figure 2

- , the Austral winter, Austral notifications and ash detected by IASI (Puyehue-Cordón Caulle eruption, 6 June 2011). and aerosols (ash) detected by GOME-2 (Grìmsvötn eruption, 23 May 2011). SO the

of ash corresponds respectively to AAI 2, under respectively corresponds globally globally : 2 2 Cordón Cordón Caulle volcano (4 - f 2011 were 2 21 - fterwards ack SO SO A cloud during tr and 5 weeks. On 4 June 2011, the eruption of notification was an ash

1 2 3 4 5 6 7 8 and and came back over Europe, was monitored during 3 weeks. The ash cloud, which travelled over Figure Figure Fig. 22. Fig. 21. on on the north coast of Norway is not related to by GOME by was under the limit of detection 3 days after the start of the eruption. of the start after the 3 days of detection limit the under was ion he largest number of 7 July). A characteristic feature of the Grìmsvötn eru feature of the Grìmsvötn 7 AJuly). characteristic

aerosols aerosols index has been super detected detect over Canada Europe, three major events o the Chilean Puyehue - while ( went southeast to the ash cloud the T

7 8 9 5 6 3 4 1 2 11 10

30 the the the

Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper . The | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | )

4 ook to avoid

Fig. 2 ( cloud cloud was not

clouds clouds t spreading spreading to the airlines

, Copahue Copahue volcano

. ). 2 is presented in 29 and and

north north ast ast to E for this arned arned and and 1 10 km Puyehue Puyehue ic ic cloud

over over East and ash different different volcanic cloud ar 1

F 1 2 an an explosive the the

nto nto the sky

Fig. Fig. the the Nyamuragira

2011).

performance performance of our notification Figure Figure 23 shows the at sed by (see

from from the

.

April April 2012, and again

of the volcan s

– December 2012). December June

able to monitor the volcanic cloud. full full spewed spewed i cloud cloud aviation warning

, 16 ,

- an altitude of of June , 23 , to specific meteorological conditions

, South Africa, Australia and

volcanic volcanic ejection drifted . th as route route of many flights ash cloud

of September 2012, in January w

e the the

st and and Brazil s

2 and and 14

ing ing the journey th SO 3 The The 1 international international route across

s the eruption of the Chilean

. than after this a Less two eruption, months

), while the ash emitted by driven driven by ing the 1 he amount of ash emitted by Nabro monitor ing ing an

T

. in emission and ash are not exactly at the same locations. locations. same at the not exactly are ash and occurred threat

ors. ors. At this time of the year and for this location, the detected detected by SACS 2 rich) and and AIRS , cancelled. cancelled.

ntinuous ntinuous activity was recorded

- produc Copahue Copahue eruption . To synthetiz ash ash of an ash cloud at and and AIRS

16 June - traffic traffic Tokyo Tokyo VAAC sent out an ash were

a volcanic plume Nabro and Puyehue eruptions and Puyehue Nabro

ed ( 6000 5999

the first day of this eruption, SO ili, ili, Argentina, Uruguay, was was critical

ed by IASI , the area

November. November. The main part of the

IASI ed to air traffic, wa th for in in Ch

that

. report 3 s s for 2012. Co in 2 in the atmosphere detect on 27

2 that detected detected by IASI un

pass Fig. Fig. ed 2

about about 10 km SO 4 ly in in 2 SO s of Etna (Italy) were also that detected by IASI ( detected by IASI

notification during during the night of 15 Satellite Satellite information

a disruption of of June 2011, Eritrean the Nabro volcano started to erupt (see Fig. 3). This explosive and ash detected by ash and Fig.

y instruments used by SACS that were ash 2 by IASI and AIRS sens th the the Nabro volcano spew and and large

l routes l routes d over several continents SO in

an an altitude of plume plume associated with : over Chile and aviation authorities in South America w the the cloud of an

23 rich and/or sometimes ash 2 - of June,

2 Summit Summit eruption

as detected by the instruments used by SACS used the instruments by as detected rich rich th SO -

rising rising to . Figure Figure w 2 : shows shows the SACS in Fig. 3 observed

c 24 was very low ( 8 the plume SO October October 2012, but no strong disruption of air as the the night of the 12 1 volcano, volcano, the Tolbachik, erupt

which which caused and ash detected by IASI (Copahue eruption, 23 December 2012). and ash detected by IASI (Nabro and Puyehue eruptions, 16 June 2011). . The 14

–

plume plume observed by IASI 2 2

major major intercontinenta 2 , no ash ash , no y to the previous eruption of Puyehue in June 2011, the Copahue’s volcanic SO SO Figure volcano (DRC). in July eruption took place at Bezymianni volcano (Kamchatka), With a cloud the nearby New Zealand New During eruption ejected a huge amount of Europe Africa and the Middle East. We can see SO eruption IASI by detected still was volcano hemisphere hemisphere during the month of June 2011 Figure Figure ). An board board from the Tokyo VAAC il rich. We can see was transported -

, nevertheless the high concentrations of SO concentrations high the , nevertheless eruption 2 3 4 5 6 7 8 9 1 (sometimes (sometimes SO

11 12 13 14 15 16 17 10 dispersing s Fig. 24. Fig. 23.

om om 2010 to 2012, the diagnosis of SACS monitoring of the volcanic activity Contrar plume plume .

2012

December Despite this Despite 25 -

composition occasionally system fr appendix In this section, we have shown the major volcanic events which have disturbed years. air We traffic can during see the the uniqueness last of 10 each eruption. This diversity is characteri same trajectory same The last (23 volcanic the area. particularly ash and northwest (NNW), thermal IR instruments were the onl The ash advisory NNW.

9 7 8 5 6 2 3 4 1 17 15 16 12 13 14 11 10