Quan>fyingtheTransportofAirintoMesoscaleConvec>veSystemUpdraVs
1
2
2
RachelPhinney ,PeterMarinescu ,SusanvandenHeever 1
2
UniversityofNebraska-Lincoln ,ColoradoStateUniversity Results:Lowvs.Mid-levelTracers
Introduc>on
Results:CaseComparison
Figure4.ThefracFonoftheiniFaltracer
amountasafuncFonofheight(m)where
theverFcalvelocityisgreaterthan5ms-1
at10:30UTC.
Scien>ficQues>on:Howmuchmid-levelairisge3ng
intoMCSupdra:s?
Methods
TheRegionalAtmosphericModelingSystem(RAMS)1wasusedto
simulatetwocasesfromtheMid-la>tudeCon>nentalConvec>veCloud
Experiment(MC3E)2,3:May20,2011andMay23-24,2011.
Figure1.NEXRADradarreflecFvity(dBZ)at2.5kmabovegroundfor(le6)20Mayat10:30UTC
and(right)24Mayat05:00UTC
Crosssec>ons
0900UTC
Figure5.Bargraphcomparisonof
T01-T02andT05-T06between7and8
kilometerson20Mayat10:30UTC.
1045UTC
TheRAMSsimula>onsu>lizedaredescribedinMarinescuetal.(2016).
Theyused1.2kmhorizontalgridspacingandver>calgridspacingof75
mnearthesurface,stretchedto500mnear4kmabovegroundlevel.
Forthestudyhere,thesesimula>onswererestartedduringtheMCS
maturestagesandrunfor2hours.Tracerswereplacedinfrontand
behindtheMCSatmul>pleal>tudestostudyairtransportwithin
MCSs.
TracerIni>aliza>on
T03
T02
T01
Therewere16tracer
heights,each1kminthe
ver>cal,and150kmx150
kminthehorizontal(Figures
2and3).Eachlayerwas
populatedwiththesame
totalnumberoftracers.
Figure2.(top).CrosssecFonofthe20May
caseat09:00UTCshowingthelocaFonof
thetraceriniFalizaFon.EachsecFonis1km
thickand150kmx150kminthehorizontal.
Totalcondensateiscontouredinblack.
Figure3.(bo\om).Planviewofthe20Mayat
09:00UTCwithverFcallyintegrated
condensatecontouredandthetracerlocaFons
outlinedinblack.
Figure7.SameasFigure4,but
for24Mayat03:30UTC.
Resultsofthisgraphare
comparedwiththatofFigure4.
Notethechangeinx-axisscale.
1)  Greateramountsoftracersareobservedinthe24Maycase.
2)  Thedifferencebetweenlow-levelandmid-leveltracersis
smallerinthe20Maycasei.e.mid-levelairprovidesalarger
frac>onoftheairwithinupdraVsinthe20Maycase
comparedtothe24Maycase.
•  Toseehowmanytracerswereenteringintotheupper
regionsofthestormthetotalquan>>esoftracersbetween
7and8kilometerswereevaluated.Itwasdiscoveredthatin
thisregiontherewere1.5>mesmorelow-leveltracersthan
mid-leveltracers(Figure5).Thisisconsistentwithour
findingswhenlookingatthetracerquan>>esforalheights.
height(m)
•  Thetotalquan>>esofthe
tracerswithintheupdraV
showthat6%ofairfromthe
low-levels(T01-T02)and3%of
airfromthemid-levels(T05T06)arecontainedwithinthe
MCSupdraVs(w>5ms-1)aVer
1.5hours.
•  Resultsfromthe24Maycase
aswellasother>messhow
similarresults.
height(m)
AnMCS(MesoscaleConvec>veSystem)isdefinedasathunderstorm
withacon>nuousprecipita>onregionatleast100kilometersinthe
horizontaldirec>on(AMSGlossary).
Airhasdis>nctcharacteris>csatdifferentlevelsthroughoutthe
atmosphere.It’sknownthatairnearthesurfaceentersintoMCS
updraVs,butwhataboutairfromthemid-levels?Thecharacteris>csof
airintheselayers,suchasthedrynessofthelayerortheaerosol
content,couldimpacttheMCSmicrophysicsanddynamics.
height(m)
Bothoftheseobserva>onsarethoughttobepartlyduetothe
strongerupdraVsaswellasthelargerupdraVregioninthe24May
casewhichhassignificantlymoreupdraVsthan20Maycase
(Figure8).Thegreateramountoftracersobservedwithinthe
convec>velineinthe24Maycasewerealsopartlyduetothe
northernadvec>onoftracersbywindsinthe20Maycasewhich
meantthatthesetracersdidnotbecomeentrainedintothe
updraV.
24May,2011
20May,2011
T01-T02
T05-T06
T09-T10
Figure6.CrosssecFonat35.1oNfor20Maycaseat(le6)
09:00UTCand(right)10:45UTC.T01-T02iscontouredinblue,
T05-T06iscontouredingreen,andT09-T10iscontouredinred
atavalueof9e-6.Totalcondensateiscontouredinblack.
Conclusions
•  Asexpected,morelow-levelairiswithinMCSupdraVs(6%comparedto3%).Thisalsoshows,
howeverthatmid-leveltracersarepresentwithinMCSupdraVsinamountsthatcouldhaveimpacts
onthemicrophysicsanddynamicsofthesystem.
•  UpdraVstrengthandwidthoftheupdraVregionmayimpacttheamountofmid-leveltracers
ge[ngintoMCSupdraVs.
FutureWork
•  AnalyzetracersplacedbehindtheMCS
•  ComparetracerstoCCNconcentra>ontodeterminehowmanyaerosolsgetac>vatedandwhereinac>vated
aerosolsendup.
Figure8.Planviewplotsfor(le6)20Maycaseat10:30UTCand(right)24Maycaseat03:30
UTCwithverFcalvelocitygreaterthan5ms-1contouredinred.Totalcondensateiscontouredin
black.
Acknowledgements
ThisworkhasbeensupportedbytheNa>onalScienceFounda>onResearchExperiencesfor
UndergraduatesSiteinClimateScienceatColoradoStateUniversityunderthecoopera>ve
agreementNo.AGS-1461270andtheDepartmentofEnergy.GrantNumber:DE-SC0010569.
References
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nuclea>on,regenera>on,deposi>on,andradia>on.J.Appl.Meteor.Climatol.,inpress.
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Soc.
3.Marinescu,P.J.,andCoauthors,2016:MicrophysicalStructureandEvolu>onofLatentHea>ngProfilesinTwo
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Formoreinforma>on,[email protected]