Moist Convection and the 2010-2011 Revival of Jupiter's South Equatorial Belt

6.9 MB·

by  Leigh N. Fletcher

Moist Convection and the 2010-2011 Revival of Jupiter’s South Equatorial Belt
LeighN.Fletchera,G.S.Ortonb,J.H.Rogersc,R.S.Gilesd,A.V.Payneb,P.G.J.Irwind,M.Vedovatoe
aDepartmentofPhysics&Astronomy,UniversityofLeicester,UniversityRoad,Leicester,LE17RH,UK
bJetPropulsionLaboratory,CaliforniaInstituteofTechnology,4800OakGroveDrive,Pasadena,CA,91109,USA
cBritishAstronomicalAssociation,BurlingtonHouse,Piccadilly,LondonW1J0DU,UK
dAtmospheric,Oceanic&PlanetaryPhysics,DepartmentofPhysics,UniversityofOxford,ClarendonLaboratory,ParksRoad,Oxford,OX13PU,UK
eJUPOSTeam,UnioneAstrofiliItaliani
Abstract
7The transformation of Jupiter’s South Equatorial Belt (SEB) from its faded, whitened state in 2009-2010 (Fletcher et al., 2011b)
1toitsnormalbrownappearanceisdocumentedviacomparisonsofthermal-infrared(5-20µm)andvisible-lightimagingbetween
0
November 2010 and November 2011. The SEB revival consisted of convective eruptions triggered over ∼ 100 days, potentially
2
poweredbythelatentheatreleasedbythecondensationofwater. Theplumesrisefromthewatercloudbaseandultimatelydiverge

nandcoolinthestably-stratifieduppertroposphere. Thermal-IRimagesfromtheVeryLargeTelescope(VLT)wereacquired2days
a
aftertheSEBdisturbancewasfirstdetectedasasmallwhitespotbyamateurobserversonNovember9th2010. Subsequentimages
J
over several months revealed the cold, putatively anticyclonic and cloudy plume tops (area 2.5×106 km2) surrounded by warm,
4
cloud-freeconditionsattheirperipheriesduetosubsidence.Thelatentheatingwasnotdirectlydetectableinthe5-20µmrange.The

] majorityoftheplumeseruptedfromasinglesourcenear140−160◦W,coincidentwiththeremnantcycloniccirculationofabrown
P
barge that had formed during the fade. The warm remnant of the cyclone could still be observed in IRTF imaging 5 days before
E
the November 9th eruption. Additional plumes erupted from the leading edge of the central disturbance immediately east of the
h.source,whichpropagatedslowlyeastwardstoencountertheGreatRedSpot. Thetroposphericplumesweresufficientlyvigorousto
pexcitestratosphericthermalwavesovertheSEBwitha20−30◦longitudinalwavelengthand5-6Ktemperaturecontrastsat5mbar,
-
showingadirectconnectionbetweenmoistconvectionandstratosphericwaveactivity. Thesubsidenceandcompressionalheating
o
rofdry,unsaturatedairwarmedthetroposphere(particularlytothenorthwestofthecentralbranchoftherevival)andremovedthe
t
saerosolsthathadbeenresponsibleforthefade. Dark,cloud-freelaneswestoftheplumeswerethefirsttoshowthecolourchange,
aand elongated due to the zonal windshear to form the characteristic ‘S-shape’ of the revival complex. The aerosol-free air was
[
redistributed and mixed throughout the SEB by the zonal flow, following a westward-moving southern branch and an eastward-

1movingnorthernbranchthatrevivedthebrowncolourationover∼ 200days. ThetransitionfromthecoolconditionsoftheSEBZ
v
duringthefadetotherevivedSEBcauseda2-4Krisein500-mbartemperatures(leavingaparticularlywarmsouthernSEB)and
5areductionofaerosolopacitybyfactorsof2-3. Newly-clearedgapsintheuppertroposphericaerosollayerappeareddifferentin
6
9filterssensingthe∼700-mbarclouddeckandthe2-3barclouddeck,suggestingcomplexverticalstructureinthedowndrafts. The
0last stage of the revival was the re-establishment of normal convective activity northwest of the GRS in September 2011, ∼ 840
0daysafterthelastoccurrenceinJune2009. Moistconvectionmaythereforeplayanimportantroleincontrollingthetimescaleand
1.atmosphericvariabilityduringtheSEBlifecycle.
0
Keywords: Jupiter,Atmospheres,composition,Atmospheres,dynamics
7
1
:
v
1. Introduction 2010, Jupiter’s South Equatorial Belt (SEB, between the pro-
i
X gradeSEBnjetat6.1◦SandtheretrogradeSEBsjetat17.2◦S,
Global upheavals of Jupiter’s banded structure can produce
r planetocentriclatitudes)underwentadramaticchangefrombe-
astrikingchangestotheplanet’sappearanceoveraperiodofjust
ingthedarkestandbroadestbeltontheplanettoafaded,white,
a few months, capturing the attention of amateur and profes-
zone-like state. This signalled the start of a whitening and re-
sionalobserversalikeandpromptingintenseperiodsofscrutiny
darkening cycle, known as an SEB fade and revival, that was
ofthegiantplanet(Rogers,1995). Thetemporalvariabilityof
investigatedforthefirsttimeinthethermalinfrared(5-25µm)
Jupiter’s bright, cloudy zones and darker, cloud-free belts can
to understand the temperature and aerosol changes associated
reveal the atmospheric processes shaping the gas giant’s typ-
withthe‘disappearance’(whitening)ofthebelt(Fletcheretal.,
ical appearance, including large-scale overturning, moist con-
2011b, hereafter Paper 1). Narrow-band thermal-IR images
vectivedynamics,andcloudcondensation. Between2009and
werepresentedbetweenMay2008andSeptember2010,track-
ingtheshutdownofthenormalconvectiveactivityintheSEB
throughtothefully-fadedandquiescentstateinmid-2010.
Emailaddress:[email protected](LeighN.
Fletcher) Herewepresentthefirstcharacterisationofthermalchanges
PreprintsubmittedtoIcarus January5,2017
associatedwitharevivaloftheSEB.Section2describestheco- SEBZtoexhibitcoolzone-liketemperaturesfor p>300mbar
ordinatedcampaignof5-20µmimagingnecessarytotrackthe (i.e.,withintheconvectiveregion),butnoSEBZwasdetectable
event,utilisingdatafromtheVLTandGemini-SouthinChile; at lower pressures in the radiatively-controlled upper tropo-
theIRTF,SubaruandGemini-NorthinHawaii;intandemwith sphere. Ultimately,thechangeinopacityandreflectivityofthe
amateurobserversfromaroundtheglobe.Acomprehensiveob- troposphericaerosolsobscuredthebrownchromophoresofthe
servational timeline for the revival is given in Section 3, from SEBandcausedthewholebelttowhitenover,althoughwecau-
thedetectionofSEBplumesinNovember2010tothereturnto tion the reader that no spectroscopically-identifiable ammonia
‘normal’SEBconditionsinlate2011. Thisincludestempera- ice signatures (Baines et al., 2002) have been reported during
tureandaerosolmeasurementsfrominversionsoftheinfrared thisfadedstate.
data. Section 4 presents an analogy between the SEB revival By August 2009 the SEB(S) had also begun to cloud over
plumes and mesoscale convective systems on Earth, using the andtakeonapalerappearance,andbyNovember2009itwas
dynamicsofmoistconvectiontoexplainthethermalvariations indistinguishable from the rest of the SEB. Only the SEB(N)
observedduringtheSEBrevival. remaineddarkandcloud-free(i.e.,brightat4.8µm)bytheend
of the 2009 apparition (May 2009-January 2010). During the
1.1. Historicalbackground onsetofthefade,aseriesoffivebrownbarges(cyclonic,cloud-
HistoricalaccountsofcolourchangesduringSEBlifecycles free andwarm-temperature ovals, namedB1 to B5)formed in
(Peek,1958;Rogers,1995;Sa´nchez-LavegaandGomez,1996) thepalebrownSEB(S)atprogressivelygreaterlongitudeswest
revealedsimilarpatternsduringeachfadeandrevival,enabling of the Great Red Spot (Rogers, 2011a; Fletcher et al., 2011b;
predictions for the general progression of this episodic event. Pe´rez-Hoyos et al., 2012). The first barge appeared just west
AssummarisedinPaper1,the2009-10cyclewasthefifthsince oftheGRSinJune2009,thefifthbargeformedinAugust,and
thefirstspacecraftencounterwithJupiter(Pioneer10in1973), these cyclonic regions appeared to be an unusual new feature
withSEBfadesandrevivalsoccurringbetween1972-1975(Or- oftheSEBfadedstate. Thesebargesweredarkandconspicu-
tonetal.,1981;Rogers,1995),1989-1990(Rogers,1992;Satoh ousinJanuary2010,butthesetoofadedandwereonlyfaintly
andKawabata,1992;KuehnandBeebe,1993;SatohandKawa- visible as oval outlines when Jupiter reappeared from behind
bata, 1994), 1992-1993 (Sa´nchez-Lavega and Gomez, 1996; theSuninApril2010. ByJuly2010,whenthefadewascom-
Moreno et al., 1997) and a partial fade in 2007 (Reuter et al., plete, the brown barges were only detectable as faint thermal
2007;Bainesetal.,2007). Thetwentiethcenturysawfourteen signaturesat10.8µm(sensingtemperaturesandammoniagas
suchrevivals,fromthe1919/20cycle-thefirsttobeobserved near500mbar). BythistimethewholeSEBwaspaleincolour
indetailafteraquietperiodof37years-tothe1992/93cycle and dark at 4.8 µm and 8.6 µm due to a two-fold increase in
(Rogers,1995). Thegapbetweentherevivalandthenextfade troposphericmid-IRaerosolopacitysincemid-2008.
can be anything between 2-14 years, making the onset of the
fadedifficulttopredict. 1.2. Expectationsfortherevival
The 2009-10 fade sequence can be summarised as follows Paper 1 demonstrated that the normal convective motions
(seeTable4ofPaper1). Thefilamentaryconvectionthatnor- that typify the SEB had completely shut down by mid-2010,
mallydominatesthe‘wake’tothenorthwestoftheGreatRed and suggested that this was replaced by zone-like upwelling
SpothadlargelyceasedbylateMay2009,signallingtheonset of fresh condensables like NH gas. We hypothesised that re-
3
of a more quiescent state for the SEB. By July a band of ele- moval of the white colouration would require sublimation of
vatedcloudopacityfilledthecentreoftheSEB(knownasthe the ices due to a temperature rise, leading to a revival of the
SEB zone, or SEBZ), separating the cloud-free northern and SEB.Buthowwouldsuchatemperatureriseoccur? Wouldit
southern components of the belt, the SEB(N) and SEB(S), re- be a slow or rapid change? Historical records (Rogers, 1995;
spectively. This increased cloudiness was observed at 4.8 and Sa´nchez-LavegaandGomez,1996)suggestthatasinglewhite
8.6 µm, which sense opacity near the 2-3 bar level and 800- convective plume (the SEB disturbance, or SEBD) would ini-
mbar level, respectively, and preceded the visible fade of the tiate the process by punching through the stagnant, quiescent
SEBbyseveralmonths. Usinga3-layeraerosoldistributionto white cloud layer. The disturbance would then spread in a vi-
modelvisiblereflectivity,Pe´rez-Hoyosetal.(2012)confirmed olent and eruptive manner, producing three distinct branches:
thatthefadewasdetectedearliestatthedeepest-sensingwave- a central branch where the interior of the SEB is reviving; a
lengths, and caused a substantial increase in the optical thick- northern branch moving eastward to restore the SEB(N); and
nessofthetopmostcondensationcloud(1.0±0.4bar)andre- a southern branch of dark spots moving westward to restore
flectivity of aerosols throughout the upper troposphere (0.24- the SEB(S) (Rogers, 1995). These three branches were all
1.4 bar). Such a sequence hinted at a large-scale change dif- observed in visible-light imaging during the 2010-11 revival
fusing upwards from the deeper atmosphere and affecting all (Rogers,2011a,2016), buthowdotheyrelatetothechanging
longitudessimultaneously. Thereappearedtobenodetectable temperaturefield? Couldabelt-widetemperatureriseprecede
changeinthecloudaltitudesorcloud-trackedwindsduringthe theSEBD,graduallycreatingconditionssuitableforthecolour
fade (Pe´rez-Hoyos et al., 2012), and Fletcher et al. (2011b) change (Orton et al., 1981; Satoh and Kawabata, 1994)? Al-
speculated that enhanced vertical mixing of volatile-laden air, ternatively,therisingplumescoulddirectlyinjectlatentheatas
combinedwithcondensationinthecoolSEBZ,servedtomod- gaseous species condense out, or large-scale sinking motions
ify pre-existing aerosol layers. The upwelling also caused the surrounding small-scale plumes could warm the atmosphere
2
by subsidence and adiabatic warming. Furthermore, Paper 1 2.2. IRTF/MIRSI
suggested that the SEBD might be related to the residual cy- NASA’s Infrared Telescope Facility (IRTF) provided 7-24
clonic circulations (subsidence and warming) associated with µm imaging using the MIRSI instrument (Mid Infrared Spec-
the five brown barges: the 2007 SEBD erupted from a brown trometer and Imager, Deutsch et al., 2003), albeit at a lower
spot(Rogers,2007), andthesamemayhaveoccurredin1993 diffraction-limited spatial resolution due to the smaller diam-
(Sa´nchez-LavegaandGomez,1996). Inthefollowingsections, eter(3m)oftheprimarymirror. MIRSIfeatureda320×240
wepresentthermal-infraredimagingduringtherevivaltoshed Si:Asarraywitha0.3”pixelscaleovera1.6×1.2arcminfieldof
new light on the environmental changes associated with this view,andhadbeenobservingJupitersince2004(Fletcheretal.,
colourchange. 2010). Unfortunately, a problem with MIRSI’s electronics in
late2011,attheendofthesequencepresentedhere,meantthat
the instrument was removed from the observatory pending a
2. ObservationsandSpectralInversion significantupgrade.
2.3. Subaru/COMICS
Paper 1 focussed solely on thermal-IR observations of the
SEBfadefromtheEuropeanSouthernObservatory(ESO)Very The Cooled Mid-IR Camera and Spectrograph (COMICS,
Large Telescope (VLT) in Chile and the NASA Infrared Tele- Kataza et al., 2000) is mounted on the 8.2-m diameter Sub-
scope Facility (IRTF) in Hawaii. However, capturing such a aru telescope operated by the Japanese National Astronomi-
rapidly evolving revival event required the use of multiple fa- cal Observatory. Subaru/COMICS has provided observations
cilitiesintheM(4.5-5.2µm), N(8-13µm)andQ(17-24µm) of Jupiter since 2005, and acquired images on August 27th
bands as outlined below. Images were initially reduced us- 2011 covering 2/3 of Jupiter’s longitudes. COMICS features
inginstrument-specificsoftwareprovidedbytheobservatories. a320×240pixelarraywithasmallerpixelscale(0.133”)and
Despiking and bad pixel removal, geometrical registration by field of view (42×32”) than IRTF/MIRSI. Combined with a
fitting the limb, cylindrical reprojection and absolute calibra- large chopping amplitude than VLT/VISIR, this implied that
tionwereperformedfollowingtechniquesdescribedinFletcher Jupiter’sfulldisccanbeobservedwithouttheneedformultiple
et al. (2009b). Radiometric calibration in the 7-24 µm range pointings. COMICSusesasimilarfiltersettoVISIRinTable
was achieved via scaling the central meridian radiances in a 2.
particularimagetozonalmeanVoyager/IRISandCassini/CIRS
spectraconvolvedwiththerelevantfilterfunction,avoidingthe 2.4. Gemini-S/TReCS
regionoftheSEB.Alllatitudesinthisstudyareplanetocentric, The Thermal-Region Camera Spectrograph (TReCS, De
alllongitudesarequotedforJupiter’sSystemIIIWest. Thefol- BuizerandFisher,2005)onGemini-Southwasacquiringspec-
lowingsubsectionsbrieflydescribetheseveninstrumentsused troscopicobservationsofJupiterin2010and2011thatwillbe
inthiswork. thesubjectofafuturepublication. However,acquisitionimag-
ing at 8.6 and 10.3 µm captured the progress of the SEB re-
2.1. VLT/VISIR vivalonNovember21st2010andJuly27th2011. TheTReCS
320×240detectorand0.09”pixelscaleprovidedasmallfield
The VLT Imager and Spectrometer for the mid-infrared ofviewof28.8×21.6”which,whencombinedwiththesmall
(VISIR Lagage et al., 2004) on the 8.2-m diameter Melipal chopping amplitude of 15”, means that the Jupiter images are
telescope has been used to study Jupiter since 2006. We ob- often obscured by the negative chopped beam. Although at-
servedtheSEBrevivalonmultipleoccasionsbetweenNovem- temptsweremadetoremovethis,theresultingimagesaregen-
ber2010andSeptember2011(Table1). WewereawardedDi- erallyofalowquality. TReCSwasretiredfromGemini-South
rectorsDiscretionaryTime(programme286.C-5009)andregu- inearly2012tomakewayfornewinstrumentation.
larobservations(programme087.C-0024)toextendtheprevi-
2.5. Gemini-N/NIRI
ousstudiesoftheSEBfade(Fletcheretal.,2011b). Observa-
tions were acquired in 8 discrete filters (Table 2) between 7.9 Director’s discretionary time on the Near InfraRed Imager
and 19.5 µm, chopping and nodding to remove the sky back- and Spectrometer (NIRI, Hodapp et al., 2003) on Gemini-
ground.VISIR’s256×256pixelarrayandpixelscaleof0.127” North was awarded to study the onset of the SEB revival,
providedafieldofviewof32×32”. Combinedwiththemax- and successfully captured the central branch on three dates in
imum chopping amplitude of 25”, it was necessary to observe November 2010. Each observation consisted of hundreds of
northern and southern hemispheres independently (and some- short0.2-secondexposuresat4.7µmwithouttheadaptiveop-
times on different nights). A full image sequence of a single tics system, selecting only the best frames (i.e., those with
hemisphere took approximately 50 minutes to complete. The the least blurring due to atmospheric seeing) for coaddition.
ESOdatapipelinewasusedforinitialreductionandbad-pixel Thistechnique,sometimesreferredtoas‘luckyimaging’(e.g.,
removalviaitsfront-endinterface,GASGANO.TheVISIRob- Mousis et al., 2014), permits spatial resolutions approaching
servationsofJupiterinSeptember2011werethefinalonesbe- diffraction-limited seeing (0.15” from an 8.1-m observatory at
fore the instrument was removed from the telescope for refur- 4.7µm). NIRI’s1024×1024pixelInSbarray,combinedwith
bishmentbetween2012-2015. the f/32cameraprovidinga0.022”pixelscale,limitsthefield
3
Table1:InfraredobservationsoftheSEBrevival.
Date Instrument ProgrammeID Comments Figures
2010-11Apparition
2010-11-04 IRTF/MIRSI 2010B010 Centrallongitudebeforerevivalplume 3,4
2010-11-11 VLT/VISIR 286.C-5009 Revivalplumeat8.6µm 4
2010-11-13 IRTF/SpeX 2010B010 Revivalplumeat5µm 5
2010-11-13 VLT/VISIR 286.C-5009 Non-revivinghemisphere,allfilters 4
2010-11-16 IRTF/NSFCAM2 2010B010 Centralbranchat5µm 5
2010-11-18 Gemini-N/NIRI GN-2010B-DD-3 5-µmluckyimaging 5
2010-11-21 Gemini-S/TReCS GS-2010B-Q-8 Acquisitionimaging,centralbranch 4
2010-11-21 Gemini-N/NIRI GN-2010B-DD-3 5-µmluckyimaging 5
2010-11-28 IRTF/NSFCAM2 2010B010 Centralbranchat5µm 5
2010-11-30 Gemini-N/NIRI GN-2010B-DD-3 5-µmluckyimaging 5
2010-12-01 VLT/VISIR 286.C-5009 Revivalcentralbranch,allfilters 4,6,7
2010-12-05/06 IRTF/MIRSI 2010B010 Centralbranch 4
2010-12-05 IRTF/NSFCAM2 2010B010 Centralbranchat5µm 1,5
2010-12-10 IRTF/NSFCAM2 2010B010 Centralbranchat5µm 5
2011-01-06 IRTF/NSFCAM2 2010B012 5µm 5
2011-01-09 IRTF/NSFCAM2 2010B012 5µm 5
2011-01-16 VLT/VISIR 286.C-5009 Revivalcentralbranch,allfilters 6,8
2011-01-27 IRTF/SpeX 2010B012 Maturerevivalat5µm 5
2011-01-27/31 VLT/VISIR 087.C-0024(A) Revivalglobalcoverage 8,9
2011-03-01 IRTF/NSFCAM2 2011A010 5µm 5
2011-12Apparition
2011-07-25/26 IRTF/MIRSI 2011A010 Lowquality,overlappedGemini-S/TReCS Notshown
2011-07-27 Gemini-S/TReCS GS-2011A-Q-11 Acquisitionimaging,maturerevival 8
2011-08-27 Subaru/COMICS O11154 Near-globalmapinallfilters 10
2011-08-29/31 IRTF/NSFCAM2 2011B027 5µm,Maturerevival 1
2011-08-30 IRTF/MIRSI 2011B027 Maturerevival 8
2011-09-13/18 VLT/VISIR 087.C-0024(B) Post-revivalglobalcoverage 8,11
2011-11-25 Gemini-S/TReCS GS-2011B-Q-11 GRSconvectionrestarted 8
Table2:VLT/VISIRFiltersusedinthisstudy.ApproximatepeaksofthefiltercontributionfunctionsarebasedonFletcheretal.(2009b).
Name Wavelength(µm) Sensitivity Approx. Pressure(mbar)
J7.9 7.90 StratosphericT(p) 5
PAH1 8.59 AerosolsandT(p) 650
SIV2 10.77 NH ,aerosols,T(p) 400
3
NeII 1 12.27 StratosphericT(p)andC H 6
2 6
NeII 2 13.04 TroposphericT(p) 460
Q1 17.65 TroposphericT(p) 200
Q2 18.72 TroposphericT(p) 270
Q3 19.50 TroposphericT(p) 400
4
of view to 22×22”. This was mosaicked across the disc on model was minimised whilst ensuring smooth and physically-
each of the three dates, but only those positions showing the plausibleverticalprofilesusingpreviouslyderivedtemperature
SEB revival are considered in this study. These data were not andchemicaldistributionsaspriors. Althoughbettersuitedto
absolutelycalibrated,butthefluxeswerescaledtomatchthose spectroscopy, this spectral inversion algorithm was applied to
ofourIRTFobservations(seenextsection). photometricimagingbyFletcheretal.(2009b)andcanbeused
to map Jupiter’s tropospheric and stratospheric temperatures,
2.6. IRTF/NSFCAM2andSpeX alongwithestimatesofthespatialdistributionofmid-infrared
The4.7-µmobservationsfromGemini-N/NIRIweresupple- aerosolopacity. ThereaderisreferredtoFletcheretal.(2009b)
mentedbyIRTFobservationswithlowerspatialresolutionbut foradescriptionofthesourcesofspectrallinedata,theconver-
better time coverage throughout the fade/revival cycle. We sion of line data to k-distributions for rapid spectral inversion,
primarily used the NSFCAM2 instrument (Shure et al., 1994) andtheinputstoJupiter’saprioriatmosphericstructure.
to extend the time sequence shown in Fig. 7 of Paper 1, Temperatures in the troposphere and stratosphere were de-
monitoring the changing 4.7-µm emission. NSFCAM2 had a fined on a grid of 80 layers between 10 bar and 0.1 mbar and
2048×2048pixelarraywitha0.04”pixelscale,equatingtoa thefullT(p)isretrievedateverylocation. Retrievalsofaerosol
large 81×81” field of view for efficient mapping of Jupiter’s opacity, NH and C H simply use a scaling of (i) a compact
3 2 6
fulldisc. NSFCAM2wasremovedfromthetelescopeinearly cloudwithabaseat800mbarandextinctioncross-sectionde-
2012fortheinstallationofanewinfrareddetector,sotheSEB terminedby10-µmradiusNH ice(Fletcheretal.,2009a);(ii)
3
revival sequence was among the last observations acquired by an NH profile well-mixed at 100 ppm for p > 800 mbar and
3
this facility with the old array. Standard stars were not sys- decliningathigheraltitudesduetobothcondensationandpho-
tematically acquired to calibrate the NSFCAM2 observations, tolysis (e.g., Achterberg et al., 2006); and (iii) a C H profile
2 6
so we adopted the relative radiometric calibration technique increasingwithheightinthestratospherefollowingNixonetal.
of Ortiz et al. (1998) from their study of NEB hotspots from (2007). Withonlyeightphotometricpointsdefiningeachspec-
IRTF/NSFCAM data between 1993-1997. Finally, the NSF- trum, this inversion suffers from low vertical resolution and
CAM2 images were supplemented by guide-camera observa- degeneracies between temperature, aerosols and composition
tions from the SpeX instrument (Rayner et al., 2003). These (particularly for p > 400 mbar) that manifest as large uncer-
used a 512 × 512 pixel array with a larger 0.12” pixel scale taintiesonretrievedquantities(Fletcheretal.,2009b). Asare-
(60 × 60” field of view), resulting in lower-quality imaging sult, novariabilityofammoniaorethanewasdetectedoutside
than NSFCAM2. Nevertheless, they are useful for extending of the uncertainties on the spectral inversion. The spatial and
thetimeseriesofthe4.8-µmobservations. temporalvariabilityoftemperaturesandaerosolopacityduring
theSEBrevivalsequencewillbediscussedbelow.
2.7. AmateurImaging
Thethermalimagingfromprofessionaltelescopesissupple- 3. Results: TheSEBRevivalTimeline
mentedthroughoutthisarticlebyvisible-lightimagesfromnu-
merous amateur observers. Images were submitted to the JU- Interpreting such a complex, evolving phenomenon from a
POS project1, British Astronomical Association2 and ALPO- seriesofincompleteinfraredsnapshotswasaconsiderablechal-
Japan3. Some are also available via PVOL (Planetary Virtual lenge. ComprehensivereportsontheSEBrevivalhavebeenas-
Observatory and Laboratory4). These three-colour images are sembledfromamateurimaging(e.g.,Rogers,2011a,b;Rogers
typicallyobtainedfrom20-41cmaperturetelescopesusingthe and Adamoli, 2015; Rogers, 2016), and we summarise those
webcam-image-stackingtechnique(Mousisetal.,2014;Karda- pointsdirectlyrelatedtotheinfraredimaginginthefollowing
sisetal.,2015). Imagesweregeometricallyregisteredandcon- sections. Thissectionisorganisedasfollows: Section3.1de-
vertedtocylindricalmapsusingtheWinJUPOSprogram(cre- scribes the initial disturbance; Section 3.2 describes the early
atedbyG. Hahn), whichisavailableathttp://jupos.org. Limb evolutionofthecentralbranchinNovember2010;Section3.3
darkeningisempiricallycorrectedforusingbest-fitcurves.The presentsourfirstmulti-spectralviewsoftherevivalcomplexin
namesoftheobserversandobservationtimesaredescribedin December2010;thedevelopmentofthenorthernandsouthern
theimagecaptions. branchesisrevealedinSection3.4,includingtheproductionof
astratosphericwaveabovetherevivingSEBinSection3.5;and
2.8. SpectralInversion Section3.6describesthelatestagesoftherevivalandthereturn
Cylindrical radiance maps in VISIR N- and Q-band filters to‘normal’conditionsinJuly-September2011. Asummaryof
were used to form crude spectral image cubes for analysis us- thethermalandaerosolchangesisdescribedinSection3.7,and
ing an optimal estimation retrieval algorithm, NEMESIS (Ir- thekeyeventsduringthetwelvemonthsoftheSEBrevivalare
winetal.,2008),followingidenticalproceduresoutlinedinPa- summarisedinTable3.
per 1. The residual between the data and the spectral forward Beforeexploringthedetailsoftherevival,NSFCAM25-µm
observations in Figs. 1 and 2 reveal the general structure and
consequencesofthisevent. Fig. 1comparesvisibleand5-µm
1http://jupos.org
maps mid-revival (December 2010) and post-revival (August
2www.britastro.org/sectionfront/15
3http://alpo-j.asahikawa-med.ac.jp 2011), showing the re-establishment of the typical appearance
4www.pvol.ehu.es of the SEB, both in visible light (dark brown coloration) and
5
e (a ) Vis ible L ight Dece mbe r 201 0
d
u 40
t
ti
a
L 20
NEB
c
ntri 0 EZ SEBn Central branch Northern branch
e SEB
oc -20 SEBs Front
t Southern branch
e
n -40
a
Pl 36 0 33 0 30 0 27 0 24 0 21 0 18 0 15 0 12 0 9 0 6 0 3 0 0
System III West Longitude
e ( b) N SFCA M2 4 .70 µ m D ecem ber 2010
d
u 40
t
ti
a
L 20

c
tri 0 Northern branch
n
e SEB(N)
c -20
o
et Southern branch
n -40
a
Pl 36 0 33 0 30 0 27 0 24 0 21 0 18 0 15 0 12 0 9 0 6 0 3 0 0
System III West Longitude
e (c) N SFC AM2 4.70 µ m Augu st 20 11
d
u 40
t
ti
a
L 20

c
tri 0
n
e
c -20
o
t
e
n -40
a
Pl 36 0 33 0 30 0 27 0 24 0 21 0 18 0 15 0 12 0 9 0 6 0 3 0 0
System III West Longitude
e (d) V isible Light Aug ust 2 011
d
u 40
t
ti
a
L 20
c NEB
tri 0 EZ
n
e
c -20 SEB
o
t
e
n -40
a
Pl 36 0 33 0 30 0 27 0 24 0 21 0 18 0 15 0 12 0 9 0 6 0 3 0 0
System III West Longitude
Figure1:GlobalmapsofJupiterinvisiblelightandat5µmfromNSFCAM2,assembledovermultiplenightsin2010and2011,showingtheSEBinthemiddleoftherevivalandafter
therevivalwascomplete.Theprominentfeaturesoftherevival(thenorthern,centralandsouthernbranches),aswellasthedirectionsofthezonaljets(theSEBnandSEBs)thatborder
theSEB,arelabelled.Thevisiblelightmapinpanel(a)wasassembledbyM.VedovatofromimagesbetweenDecember4th-5thbyT.Kumamori,C.Go,D.ParkerandK.Yunoki.The
5-µmimageinpanel(b)wascreatedfromimagesonNovember27th,December5thand6th2010.The5-µmimageinpanel(c)wascreatedfromimagesacquiredonAugust29th,31st
andSeptember1st2011.Thevisiblelightmapinpanel(d)wasassembledbyM.VedovatofromimagesbetweenAugust29th-30thbyM.Jacquesson,C.GoandA.Wesley.
6
(a) SEB Fade Sequence (2008-2010)
2008-05-27
1.0
2008-06-16
2008-07-10
e 0.8 2008-07-27
c 2008-08-07
n
a 2008-09-24
di
a 0.6 2009-07-20
R
2009-08-06

d
e 2009-08-18
alis 0.4 2009-08-27
m 2010-06-24
or 2010-06-30
N 0.2 2010-07-01
2010-09-03
0.0 2010-09-05
60 50 40 30 20 10 0 -10 -20 -30 -40 -50 -60
Planetocentric Latitude
(b) SEB Revival Sequence (2010-2011)
2010-11-05
1.0
2010-11-16
2010-11-16
2010-11-27
e 0.8
c 2010-11-28
n
a 2010-12-06
di
a 0.6 2010-12-10
R
2011-01-06

d
e 2011-01-09
alis 0.4 2011-03-01
m 2011-03-01
r 2011-08-29
o
N 0.2 2011-08-29
2011-08-31
2011-08-31
0.0
2011-09-01
60 50 40 30 20 10 0 -10 -20 -30 -40 -50 -60
2011-09-01
Planetocentric Latitude
Figure2:Central-meridianbrightnessesextractedfromallNSFCAM2imagesat4.7µmduringtheSEBfadeandrevivalsequence.Radianceswereaveragedwithin±50◦longitudeofthe
centralmeridianforeachimage.ThetoppanelisidenticaltothatshownbyFletcheretal.(2011b),thebottompanelshowsthenewdatabetweenNovember2010andSeptember2011.In
theabsenceofanabsoluteradiometriccalibration,allradiancevalueshavebeennormalisedsothattheequatorialbrightnessremainsapproximatelyunchanged.Inadditiontotherecovery
ofbrightnessovertheSEB,anexpansionandcontractioneventcanbeobservedintheNEBbetween2009-2011.
7
in the infrared (bright at 5 µm, indicating a clearing of cloud werenoaxisymmetricchangestotheSEBoncetheplumeerup-
opacity). Thecompleteclouding-overoftheSEBinlate2010 tionhadstarted,andthatthesourceoftherevivalwaslocalised
madethebeltalmostindistinguishablefromtheequatorialzone inlongitude.
(EZ)andtheSouthTropicalZone(STropZ),withtheexception Inspection of the revival plume (WS1) images on Novem-
of the narrow lane of emission from the northern edge of the ber 11th (day 2, Fig. 4b) shows that the visibly-bright central
SEBnear7◦S.Furthermore,theGreatRedSpotappearedvisi- plume was associated with a decrease in brightness tempera-
blyredandisolatedinthefadedbeltandindistinguishableat5 ture of ∼ 10 K compared to the surrounding faded SEB. Fur-
µm(Fig.1a-b),whereasitsperipherywasonceagaincloudfree thermore, there was no obvious injection of latent heat from
andbrightbyAugust2011(Fig. 1c). Fig. 2showstheevolu- condensation at the altitudes probed by this filter. Any warm-
tionof5-µmemissionthroughoutthefadeandrevivalsequence ing associated with the first plume eruption must therefore be
(2008-2011)5. Althoughtherevivalwasacomplexfunctionof located at high pressures (p > 0.5 bar), below the altitudes to
longitude,theneteffectwasaten-foldincreaseintheemission whichVISIRissensitive. Theperipheryoftheplumeappeared
at5-µmoveraperiodofafewmonths. warmer and asymmetric, with a ‘tail’ of brighter emission to
thesouthwestthatcoincideswithvisibly-darkstructuresinthe
3.1. InitialSEBdisturbanceandrevivalsource amateurimaging. Thesedarkstructuresusuallyformedonthe
Amateurobserversfirstnotedadramaticbrightplumeinthe westwardsideofthebrightplumeswithin2-3daysoftheplume
faded SEB on November 9th 2010 (day 0), which went on to appearing(Rogers,2011a,2016). Thestructuressubsequently
become the source of the SEB revival (white spot 1, WS1 at extendednorthwardtoformadark‘lane’thatmarkedthewest-
15.1 ± 0.2◦S and 148◦W, Rogers, 2011a, 2016). Prior to the ernboundaryofacellsurroundingtheplume. Theextensionof
eruptionofWS1,IRTF/MIRSIinfraredimagingonNovember the plume and peripheral warming to the southwest is consis-
4th(Fig. 3, fivedaysbeforetheoutbreak)showedarelatively tentwiththeshearbetweentheprogradeSEBnjetnear7◦Sand
bland,quiescentSEB,withonenotableexception.Visible-light theretrogradeSEBsjetnear17◦S.
imaginghadshownthatWS1eruptedfromthewhitenedrem- ThedecreaseinbrightnesstemperatureassociatedwithWS1
nantofcyclonicbargeB2thathadbeenpresentearlierin2010 could be caused by two factors - adiabatic upwelling, expan-
(Rogers,2011a;Pe´rez-Hoyosetal.,2012;Rogers,2016). The sion and cooling (near 500-600 mbar) within a rising plume,
IRTF images in Fig. 3 confirm that this barge B2 remained and/or a sharp rise in the aerosol optical depth to block out
warmer than its surroundings: images at 9.8 µm (sensing a the 8.6-µm emission. Without multi-spectral imaging we can-
combination of ∼ 400-mbar temperatures and ammonia opac- notdistinguishbetweenthesetwoscenarios,butforwardmod-
ity)and13.2µm(sensing∼ 500-mbartemperatures)showthe elling indicates that the aerosol opacity must increase ten-fold
presence of a small, warm sector at 16◦S, 144◦W, coincident at the plume location if temperatures are assumed to be con-
with the whitened remnant of barge B2. The sector spanned stant. Similarly, the slight increase in brightness temperature
approximately 3◦ longitude (∼ 3600 km) and 2◦ latitude. The atthesouthwesternperipheryislikelyduetosubsidence,adia-
cyclonic warm region was not observed at other wavelengths baticwarmingandtheinitiationoftheicesublimationtobegin
that sense higher, cooler altitudes, and did not produce cloud- to reveal the dark underlying belt. 5-µm images obtained by
freeconditionssensedat4.8and8.7µm(Fig. 3). IRTF/SpeXandIRTF/NSFCAM2onNovember13thand16th,
AftertheeruptionofWS1fromthiscyclonicbarge,thesub- respectively(Fig.5a-b,day4to7)donotreadilyshowtheindi-
sequent evolution of the plume is shown via a comparison of vidualplumes(whichwouldappeardarkatthiswavelengthdue
8.6-µm and visible-light imaging in Fig. 4. Christopher Go totheirhighopacity),butdorevealtheincreasedemissionfrom
(Philippines)firstobservedWS1at12:30UTonNovember9th regions immediately west of WS1. This decrease in aerosol
(Fig. 4b), which was confirmed one rotation later by Donald opacityisconsistentwithsubsidencethroughthe2-3barcloud
Parker (USA) and Gary Walker (USA), when it was already deck,warmingandclearingaerosolsinthedarkerregionssur-
brighter.Insubsequentrotationsitwasreportedasthebrightest roundingtheplume.WS1wasdiscernibleforjustfivedays(the
spotontheplanetbymanyobservers,particularlyinCH -band darkerlanecouldbeseenforeight,Rogers,2011a,2016), but
4
imagingat889nm,suggestiveofaconvectiveplumereaching was just the first of many such eruptions at the revival source
highabovethequiescentSEBcloudtops. Thefirstinfraredim- region.
ageofthisrevivalplumeat148◦WwasacquiredbyVLT/VISIR
onNovember11th(day2,Fig. 4b)6. Inaddition,VISIRimag- 3.2. PlumeEvolutioninNovember2010
ingwasacquiredtwodayslateronNovember13th(day4),but
targeted the still-faded SEB on the opposite hemisphere away FromNovember9thtoDecember1st(days0-22,Fig. 4and
from the erupting plumes (Fig. 4c). This confirms that there Fig. 5),Rogers(2011a,2016)reportedthreeadditionalplumes
eruptingclosetotheoriginalsourceofWS1,plusfoursimilar
plumesarrangedinalinealongtheleadingedgeofthecentral
5Figs.1and2alsoshowan‘expansionevent’oftheNEB,whichincreased branch(seebelow). Eachplumefromthesourcesubsequently
inlatitudinalextentin2009beforereturningtoanarrowerstatein2011.These appearedasthecentreofalargercell,borderedtothewestby
NEBexpansioneventsoccuronceevery3-5yearsandwillbethesubjectofa
thedarkerlane. Multipleplumesweresometimesactiveatthe
futurestudy.
6Circumstancesoutsideofourcontrolmeantthatonlyan8.6-µmacquisition same time, and new plumes appeared every 2-6 days between
imagewastakenonNovember11thratherthanafullfilterset November 9th and December 13th 2010. By December 2010,
8
Table3:Timelineofeventsinthe2010-2011Revival.Foracompaniontablecoveringthefade,pleaseseeFletcheretal.(2011b).
Time Event PossibleImplication
2010-Jul-Nov SEBfullyfaded(Fletcheretal.,2011b). SEB(S)(narrowandundulat- SEBfadecomplete.
ing) and SEB(N) are detectable at 8.6 µm, barges cannot be distinctly
observed (except at 10.8 µm); central SEB covered by high opacity
cloud.
2010-Sep-21 Jupiteratopposition Centreof2010/11apparition.
2010-Nov-04 BrownbargeB2stillfaintlyvisibleinIRTF/MIRSIimaging
2010-Nov-09 C.GoreportsfirstevidenceofSEBdisturbance(WS1)andrevival RevivalofSEBbegins.
2010-Nov-09-17 Emergence of new white plumes WS2, 3 from the location of former Bargeastheplumesource.
bargeB2
2010-Nov-21 Notable cloud holes and visibly-dark patches extending west along
SEB(S)
2010-Nov-19-30 Newplumeseruptingfromleadingedgeratherthanoriginalsource.
2010-Dec Frequencyandvisibilityofplumesbeginstodecrease. Storedpotentialenergybeginstobe
exhausted.
2010-Dec-11 NorthernbranchreachestheGRS.
2011-Jan Revivalspreadover100◦longitude;firstmajordarkspotsonSEB(N).
2011-Jan-05 NorthernbranchbeginstoformadarkcollararoundtheGRS.
2011-Jan-08 LeadingedgeofSouthernbrancharrivesatGRS. SEB(S)revivalalmostcomplete.
2011-Feb-05 Lastreportedplumefromthesourceregion. Endofconvectiveactivity.
2011-Feb-20 LeadingedgeofcentralbranchreachedGRS.
2011-Apr-06 SolarConjunction
2011-May-Jun Darkcolorationrestoredatalllongitudes.
2011-Aug-Sep General quiescence of SEB and formation of new, smaller cyclonic Potentialforarenewedfade.
barges.
2011-Sep-21 Firstsignsof‘normal’convectionNWoftheGRS. Revivalcyclehascompleted.
2011-Oct-09 Jupiteratopposition Centreof2011/2012apparition.
M IRSI 4. 90 µm 2010-11 -04 23: 11UT M IRSI 8 .70 µm 2010-11 -04 23: 19UT M IRSI 13 .2 µm 2 010-11 -04 23: 25UT
0 0 0 B2
Planetocentric Latitude---321000 222200116802 Planetocentric Latitude---321000 111444345 Planetocentric Latitude---321000 112289
204 142 127
202 141
-40 200 -40 140 -40 126
16 0 150 140 130 120 110 10 0 16 0 150 140 130 120 110 10 0 16 0 150 140 130 120 110 10 0
System III West Longitude System III West Longitude System III West Longitude
0 M IRSI 7. 70 µm 2010-11 -04 23: 15UT 0 M IRSBI2 9. 80 µm 2 010-11 -04 23: 22UT 0 M IRSI 17 .2 µm 2010-11 -04 23: 28UT
Planetocentric Latitude---321000 111155550246 Planetocentric Latitude---321000 1111 33331223....5050 Planetocentric Latitude---321000 111112229012
131.0
148
-40 -40 1 30.5 -40 118
16 0 150 140 130 120 110 10 0 16 0 150 140 130 120 110 10 0 16 0 150 140 130 120 110 10 0
System III West Longitude System III West Longitude System III West Longitude
Figure3:SurveyofthefadedSEBinIRTF/MIRSIimagingonNovember4th2010,fivedaysbeforetheoutbreakat148◦W.The17.2µmimageisrepresentativeofsimilarimagesat
17.9,18.4,20.3and24.8µm.AwarmspotisvisibleintheSEBnear144◦Winthe9.8and13.2-µmfilters(asindicatedbytheyellowlines),confirmingthecontinuedpresenceofawarm
cyclonicbargeimmediatelypriortotheeruption.
9
(a) MIRS I 8.7 0 µm 2010 -11- 04 23 :19U T A. Lasala 201 0-11 -05 1 8:52 UT
0 146 0
e e
d d
u u
atit -10 144 atit -10
L L
c c
entri -20 142 entri -20
c c
o o
et -30 et -30
an 140 an
Pl -40 Pl -40
160 150 140 130 120 110 100 90 80 70 60 50 160 150 140 130 120 110 100 90 80 70 60 50
System III West Longitude System III West Longitude
(b) VISIR 8.59 µm 2010 -11-1 1 23 :56U T 150 C . Go 201 0-11- 12 1: 03UT
0 0
de 148 de
u u
atit -10 146 atit -10
L L
ntric -20 144 ntric -20
ce 142 ce
o o
net -30 140 net -30
a a
Pl -40 138 Pl -40
17 0 16 0 15 0 14 0 13 0 12 0 11 0 10 0 9 0 8 0 7 0 6 0 17 0 16 0 15 0 14 0 13 0 12 0 11 0 10 0 9 0 8 0 7 0 6 0
System III West Longitude System III West Longitude
(c) V ISIR 8.59 µm 2 010-1 1-13 00:4 1UT C. Go 2 010- 11-13 10:2 2UT
0 148 0
e e
d d
atitu -10 146 atitu -10
L L
c 144 c
ntri -20 ntri -20
ce 142 ce
o o
net -30 140 net -30
a a
Pl -40 Pl -40
330 320 310 300 290 280 270 260 250 240 230 22 0 330 320 310 300 290 280 270 260 250 240 230 22 0
System III West Longitude System III West Longitude
(d ) TR eCS 8.60 µm 2 010-1 1-21 04:1 4UT E . Mo rales 2010 -11- 21 23 :51U T
0 152 0
e e
d d
atitu -10 150 atitu -10
L L
c 148 c
ntri -20 ntri -20
ce 146 ce
o o
et -30 et -30
an 144 an
Pl -40 Pl -40
23 0 22 0 21 0 20 0 19 0 18 0 17 0 16 0 15 0 14 0 13 0 12 0 11 0 23 0 22 0 21 0 20 0 19 0 18 0 17 0 16 0 15 0 14 0 13 0 12 0 11 0
System III West Longitude System III West Longitude
( e) VI SIR 8 .59 µ m 20 10-1 2-01 01:5 6UT 152 D . Pa rker 2 010- 12-0 1 01: 44UT
0 0
de 150 de
u u
atit -10 148 atit -10
L L
c 146 c
entri -20 144 entri -20
c c
eto -30 142 eto -30
an 140 an
Pl -40 Pl -40
22 0 210 200 190 180 170 160 150 140 130 120 110 10 0 22 0 210 200 190 180 170 160 150 140 130 120 110
System III West Longitude System III West Longitude
(f ) MIR SI 8. 70 µm 201 0-12 -05 0 4:22 UT 148 G . Wa lker 2 010- 12-06 01: 23UT
0 0
de 147 de
u u
atit -10 146 atit -10
L L
entric -20 114445 entric -20
c c
o o
et -30 143 et -30
n n
Pla -40 142 Pla -40
1 80 170 160 150 140 130 120 110 100 90 80 70 1 80 170 160 150 140 130 120 110 100 90 80 70
System III West Longitude System III West Longitude
Figure4:Comparisonof8.6-µmbrightnesstemperaturemaps(sensingtemperatureandaerosolopacitynear600mbar)andvisible-lightimagingfromNovember-December2010,showing
theatmosphericconditionsbeforetherevival(a,c),duringtheinitialoutbreak(b),andfollowingthedevelopmentofplumesduringthefirstmonth(d,e,f).Darkoval-shapedregionsin
thethermalobservationsareduetoanabsenceofdataattheselocations(eitherduetocroppingbytheinstrumentalfieldofview,orobscurationbychoppedbeams).Thebrightspotat
310◦WinthevisibleimageonrowcisIo,thedarkovalinthevisible-lightimageinrowfisasatelliteshadow.Thebrightnesstemperaturescale(K)isshowninthecentreofthefigure.
10