Gravity Wave Processes: Their Parameterization in Global Climate Models

406 Pages·1997·54.518 MB·English

by  Isamu Hirota (auth.), Kevin Hamilton (eds.)

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Series I: Global Environmental Change, Vol. 50
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Gravity Wave Processes
Their Parameterization
in Global Climate Models
Edited by
Kevin Hamilton
Princeton University
Geophysical Fluid Dynamics Laboratory
Princeton, NJ 08542, USA
With 189 Figures (2 Colour Plates) and 15 Tables
Springer
Published in cooperation with NATO Scientific Affairs Division
Proceedings of the NATO Advanced Research Workshop "Gravity Wave
Processes and Their Parameterization in Global Climate Models", held in
santa Fe, USA, April 1-5, 1996
LIbrary of Congress Cataloging-in-PublicatIon Data
Gravity wave processes their parauterlzation in global cllrute
models I edIted by KevIn Hamilton.
p. cm. -- <NATO ASI series. Series I. Global envlron.ent
change : voI. 50)
"Published In cooperatIon wIth NATO SClent1flc Affairs Division."
"Proceedings of the NATO Advanced Research ~orkshop "Gravity ~ave
Processes and Their ParaJleterl;tatlon in Global Cllrute Models". held
In Santa Fe. USA. AprIl 1-5, 1996"--T.p. verso.
InclUdes bibllographlcal references and index.
ISBN.I): 978-)-642-64495-5 c·ISBN-13: 978-)-642-60654-0
001: 10.1007/978-3-642-60654-0
1. Cllrutology--MatheJiatical lIodels--Congresses. 2. GravIty
waves--Congresses. 3. Atmosphere, Upper--Mathematlcal lIodels-
-Congresses. I. Hnllton. KeVin, 1956- II. North AtlantIc
Tr~aty Organization. ScIentIfic Affairs DivIsiOn. III. NATO
A.. anced ResearCh rlorkshop "GraVity rlave Processes ahd Their
Parneterization in Global Cliute Models' 11996 Sarna Fe. [New
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PREFACE
Gravitywavescanacttotransfermeanhorizontalmomentumfromthegroundtolevels
aloft in the atmosphere or from one layer of the atmosphere to another. Flow over
topography can generate stationary gravity waves that break nonlinearly in the
troposphereandlowerstratosphere. Suchwavestransfermomentumfromthebreaking
region to the earth's surface, and thisprocessis thought to actas a significantdrag on
the eastward mean winds in the midlatitude troposphere. It is known that numerical
simulationmodels ofthe global atmosphererun withoutany attempt to impose such a
drag tend to produce results characterized by unrealistically intense eastward surface
windsinmidlatitudes. Otherprocesses(suchasconvection,jetstreaminstabilitiesetc.)
can produce gravity waves with nonzero horizontal phase speeds and which act to
transfer mean momentum between the troposphere and the middle atmosphere.
Comprehensive numerical models of the atmosphere generally produce unrealistic
simulations of the extratropical stratospheric/mesospheric circulation unless some
accountistakenoftheeffectsofthesegravitywaves. Ifcrediblesimulationsofclimate
(andpredictionsofclimateresponsetoanthropogenicforcing) aretobeobtained,some
physicallyjustifiableparameterizationofthemomentum transport due tounresolvable
gravity waves needs tobeformulated. Thisissueisnowrecognizedasoneofthemost
importantchallengesindynamicalmeteorology.
Inordertobeginaddressing thisproblemaNATO AdvancedResearchWorkshopwas
heldinSantaFe,U.S.A.,fromApril 1-5, 1996. Themeetingwasattendedbyatotalof
36scientistsfrom 10countries. Theworkshopwasnotableinbringingtogetherexperts
inobservationsandtheoryofgravitywavesalongwithrepresentativesofseveralclimate
modellinggroups. This volumeincludes26papersrepresentingcontributionsfrom 30
ofthe meeting participants and serves as anexcellentsummary ofthe scientificissues
discussed.
IwouldliketothanktheScientificAffairsDivisionofNATOforprovidingthebulkof
the financial supportfor the meeting. Additional support was provided by the World
Climate Research Programme as part ofits initiative on Stratospheric Processes and
theirRoleinClimate(SPARC) andbytheSolar-TerrestrialEnergyProgram. FinallyI
wish to thank the attendees for their enthusiastic participation at the workshop (even
through some ofthe very long sessions that were scheduled!) and for submitting the
excellentpapersthatmakeupthisvolume.
KevinHamilton
CONTENTS
SOMEPROBLEMSRELATINGTOTHEOBSERVEDCHARACTERISTICSOF
GRAVITYWAVES INTHEMIDDLEATMOSPHERE
I.Hirota
GRAVITY-WAVEPARAMETERSINTHELOWERSTRATOSPHERE
R.A. Vincent,S.I.AllenandS.D.Eckermann 7
MEASUREMENTSOFINTERMITTENCYINTHEUPPERSTRATOSPHERE
ANDMESOSPHERE
R.I.SicaandM.D.Thorsley 27
CLIMATOLOGYANDHYDRODYNAMICSOURCESOFINTERNAL
GRAVITYWAVESINTHEMIDDLEANDUPPERATMOSPHERE
N.M.Gavrilov 45
OBSERVATIONALSTUDIESOFGRAVITYWAVESASSOCIATEDWITH
CONVECTION
KS~ ~
EXPERIMENTALCONSTRAINTSONGRAVITYWAVEPARAMETERIZATION
FROMINSITUMEASUREMENTSOFTEMPERATUREANDTURBULENCE
F.-1Ltibken 69
ANALYSISOFINTERMITTENCYINAIRCRAFTMEASUREMENTSOF
VELOCITY,TEMPERATUREANDATMOSPHERICTRACERSUSING
WAVELETTRANSFORMS
1T.Bacmeister,S.D.Eckermann,L.Sparling,K.RChan,
M.LoewensteinandM.H.Proffitt 85
OBSERVATIONSOFGRAVITYWAVESWITHTHEUARSMICROWAVE
LIMBSOUNDER
D.L.WuandJ.W.Waters 103
MAINTENANCEOFTHETROPICALOSCILLATIONSOFZONAL-MEAN
WINDS INTHEMIDDLEATMOSPHEREBYCONVECITVELY-FORCED
GRAVITYWAVES
F.SassiandR.RGarcia 121
NUMERICALMODELLINGOFINERTIA-GRAVITYWAVEEMISSIONBY
FRONTSANDJETS
M.J.ReederandM.Griffiths 137
AMODELOFNON-STATIONARYGRAVITYWAVESINTHESTRATOSPHERE
ANDCOMPARISONTOOBSERVATIONS
M.I.Alexander 153
THEPROPAGATIONANDBREAKINGOFGRAVITYWAYESEXCITEDBY
FORCINGINTHETROPOSPHERE
RR.Garciaand1M.Prusa 169
ESTIMATEOFATMOSPHERICDISSIPATIONDERIVEDFROMUARSIHRDI
MEASUREMENTS
V.A. Yudin,M.A.GellerandB.V.Khattatov 187
VIII
ONTHENONLINEARINTERACTIONSBETWEENGRAVITYWAVESIN
SHEARFLOWS
J. VannesteandF.Vial 199
GRAVITYWAVESPECfRALMODELSANDTHESHAPESOFGRAVITY
WAVESPECfRAATLOWVERTICALWAVENUMBERS
C.D.WarnerandM.E.McIntyre 217
NONLINEARITYOFTHESATURATIONSPECfRUM
C.O.flines 227
SENSITIVITYSTUDIESUSINGTHEIDNESANDFRITTSGRAVITYWAVE
DRAGPARAMETERIZATIONS
C.McLandress 245
MODELINGTHESEASONALCYCLESANDEQUATORIALOSCILLATIONS
WITHAPARAMETERIZATIONOFTHEDOPPLERSPREADGRAVITY
WAVETHEORY
H.G.Mayr,J.G.Mengel,C.O.flines, K.L. ChanandN.F. Arnold 257
THEREPRESENTATIONOFSUB-GRIDSCALEOROGRAPHYINGCMs
F.LottandM.Miller 275
THEEFFECTOFPARAMETERIZEDGRAVITYWAVEDRAGON
SIMULATIONSOFTHEMIDDLEATMOSPHEREDURINGNORTHERN
WINTER1991/1992-GENERALEVOLUTION
B.N.Lawrence 291
THEPARAMETERIZATIONOFGRAVITYWAVEDRAGBASEDONTHE
NONLINEARDIFFUSIONOFWAVBSPECfRA
A.S.Medvedev,G.P. KlaassenandB.A.Boville 309
EFFECfSOFGRAVITYWAVEDRAGINTHEBERLINTROPOSPHERE
STRATOSPHERE-MESOSPHEREGCM
S.Pawson 327
THEROLEOFPARAMETERIZEDDRAGINATROPOSPHERE-STRATOSPHERE
MESOSPHEREGENERALCIRCULATIONMODEL
K.Hamilton 337
SEASONALSIMULATIONSWITHTHECANADIANMIDDLEATMOSPHERE
MODEL:SENSITIVITYTOACOMBINATIONOFOROGRAPlflCAND
DOPPLERSPREADPARAMETERlZATIONSOFGRAVITYWAVBDRAG
N.A.McFarlane,C.~&Landress andS.Beagley 351
MIDDLEATMOSPHERESIMULATIONSWITHTHEECHAM4MODEL:
SENSITIVITYTOTHEDOPPLERSPREADGRAVITYWAVB
PARAMETERIZATION
E.Manzini,N.A.McFarlaneandC.McLandress 367
THEMESOSPHEREINTHEEXTENDEDUGAMPGCM
W.A.NortonandJ.Thubum 383
SomeProblemsRelatingto theObserved Characteristics ofGravity
Wavesinthe MiddleAtmosphere
Isamu Hirota
DepartmentofGeophysics
Kyoto University
Sakyoku, Kyoto606
Japan
ABSTRACT. Acritical review is presentedofthe understandingofgravity wave character
isticsbasedonearlierobservationalstudiessincethe 1980's. Followingcommentsonthebasic
idea ofthe gravity wave dynamics and the capability ofobservational techniques, results of
rocketsonde, balloonsondeand MU radardataanalyses are brieflyrecalled. Itis stressedthat
the"climatologyofgravity wavesources"is stillopento question,eventhough we havehad
somecasestudiesofvarious processesforthe generationofgravity waves inthe loweratmo
sphere. Anotherimportantquestionistheverticaldistributionofgravitywaveactivitiesrelating
towavebreaking(and/ordissipation)processesinthestratosphereandmesosphere,inconnec
tion withseasonal variationsofthe backgroundfield. Finallycritical commentsare added on
thecurrentattemptofthegravitywaveparameterizationinGCMsbyemphasizingtheneedfor
many moredetailedobservationsinthefuture.
1. Introduction
Through the progress made in observing the middle atmosphere in the last three decades,
theclimatologyoftheglobalcirculationhas beenestablished(e.g.,CIRAmodel),andourun
derstandingofthemechanismforthegenerationandmaintenanceofthemeanzonalwindand
temperaturefield hasbeensubstantiallydevelopedin termsoflarge-scaledynamicsas wellas
radiativeandphoto-chemicalprocesses.
Inadditiontothis,around 1980,itbecamewidelyrecognizedthatverticallypropagating,in
ternalgravitywavesplayanimportantroleindeterminingthelarge-scalewindfieldinthemid
dle atmospherethrough their momentum transport and deposition. In their pioneering works
Lindzen(1981),Matsuno(1982)andHolton(1982)showedtheeffectofthebreakingofgravity
wavesonthemeanzonalflow,andinthelastdecadetherehavebeenmanyattemptstoparame
terizethegravitywaveeffectinthenumerical modellingofthemiddleatmosphereonaglobal
basis.
Itshouldbenoted,however,thatthesenumericalmodelsassumeaprioriphysicalparameters
ofgravitywavessuchaswaveamplitudesandfrequencies withouthavingsubstantialevidence
forthese in the actualatmosphere. Inthe presentpaper,therefore, Ishouldlike toreview our
observationalstudiestoclarifywhatpropertiesofgravitywavesareknownandwhatisneeded
forfuturestudies.
2. Difficultiesinobservationsofgravity waves
Sinceinternalgravity waves have largeramplitudes inassociation withtheir vertical prop-
agation in such a way as Ivl '" POI/2 '" exp(z/2H), it is easier to separate them from the
NATOAS)Series.Vol.I50
GravityWaveProcesses
TheirParameterizationinGlobalClimateModels
EditedbyKevinHamilton
©Springer-VerlagBerlinHeidelberg1997
2
backgroundflowandlarge-scalewavesinthemiddleatmospherethaninthetroposphere. MST
radars, lidars,rocketsandballoonshavebeenusedasobservationaltoolsforthispurpose.
However,thesetechniquesareessentiallybasedonsingle-stationobservationsto obtainthe
physicalquantityofgravitywavesasafunctionofheightandtimeatafixed location(theonly
exception is the recent satellite observation under development). Because ofthis limitation,
observableparametersateachstationareverticalwavelengthandDoppler-shiftedfrequency,in
additiontothemeanfield. Horizontalwavelengthandintrinsicfrequency, forexample,haveto
beestimatedindirectly with theaid oftheoretical considerations (e.g., dispersion relation) by
assumingthedominanceofmonochromaticwaves.
Moreover,inviewoftheinhomogeneousdistributionofwavesourcesandintermittentoccur
renceofgenerationprocesses, wehavetobecarefulindetectingrepresentativecharacteristics
ofgravitywavesinbothcasestudiesandlong-termstatistics.
3. Earlystatisticsformorphologyandclimatology
Inordertohaveanoverviewofthegravitywaveactivityinthemiddleatmosphereonaglobal
basis,thoughinarathercrudemanner,Hirota(1984)firstpresentedtheclimatologyofgravity
waveswiththeaidofmeteorologicalrocketobservationsgatheredatmanystationsoverseveral
years. By applying a high-pass filter to daily rocket data in the height range of20 - 65km,
windandtemperaturefluctuationswithverticalscale:S lOkmareextracted,andtheirvariances
(r.m.s.) wereusedas aroughmeasureofthegravity waveactivity. Alargeseasonal variation
witha maximuminwinterathighlatitudesas wellasevidencefor asemiannualcycleatlow
latitudeswerefoundfromthesestatistics. Thissortofclimatologyhasbeenrecentlyrevisedby
Eckermann,HirotaandHocking(1994)byexpandingthedataperiodto 1977-1987.
Hirotaand Niki (1985) madea st.atisticalstudy basedon thesamerocketdatato showthat
theshortverticalscalewindfluctuations aredue mainlytoupwardpropagatinginertia-gravity
waves, as judged from the rotation ofhorizontal wind vectors in hodographs. Note that the
degreeofellipticpolarizationofhodographsgivesusinformationabouttheintrinsicfrequency
was wellas thedirectionofhorizontal propagation ofgravity waves. Results ofthe statistics
indicatethatthedominantvaluesof f/w (j : Coriolisparameter)fall intotherangeof 0.2'"
0.4inspiteoftheseasonalchangeofthemeanflow. Thissuggestsawidevarietyofhorizontal
phasevelocities.
Itshouldbereminded, ofcourse,thatrocketsoundingsaretooinfrequenttoresolvethebe
haviourofgravity wavesintimeandaretoosparseingeographicaldistributionto resolvethe
continent-oceancontrastandthedifferencebetweenthenorthernandsouthernhemispheres.
4. Wavesourcesin theloweratmosphere
Ourgoalintheclimatological studyofgravity waves is togivefull informationabout their
effectsonthe globalcirculationofthe middleatmospherein terms ofgravity wave forcing of
themeanflow throughmomentumdeposition. Thewave varianceshowninearlyclimatology
is not necessarilythe forcing itselfbutmerely arough measureofthe dominant structureand
behaviourofgravitywavespropagatingfrombelow. Henceournextstepshouldbetoobserve
wavegenerationprocessesintheloweratmosphere.
Ithas beenassumedthatgravitywavesshouldbegeneratedinthetropospherebytheeffect
oftopography,synopticdisturbances,convectiveactivity,geostrophicadjustmentaroundthejet
streamandshearinstabilities,butinthesecasesdetailsarepoorlyknownandrelyonafewcase
studies.
3
As regards thetopographiceffecton gravity wave generation, Sato (1990) madeadetailed
analysisofverticalwinddisturbancesinthetroposphereandlowerstratosphereasobservedby
theMUradaratShigaraki,Japaninwintertimewhenthetroposphericwesterliesaredominant.
Inastatisticalapproach,sheshowedthattheverticalwinddisturbancesareduemainlytogravity
waves generated by the effectofmountain trains located to the westofthe MU radarsite. It
is quite interesting to note that, among 8 observation periods within 1985-1987, the gravity
waveintensityisnotuniformbutratherintermittent,i.e.,activeperiodsandquietperiodsexist,
suggestingthatthegenerationofgravitywavesbytopographyisnotsimplyafunctionofsurface
winds.
Concerningwavegenerationfromthemid-latitudejetstream,HirotaandNiki(1986)madea
casestudyofinertia-gravitywavesaroundtheintensewesterliesoverJapaninwinterusingthe
MUradar. Fromtheirhodographanalysis,theyfoundthatthedirectionofhorizontalwindvector
rotation,namelythedirectionofverticalpropagation,isoppositeaboveandbelowtheheightof
thejetcore(~ llkm). Thisfactstronglysupportsthetheoreticalideaofthejetstreamasawave
source. Thisanalysis wasextendedby Kitamuraand Hirota(1989)overtheJapaneseislands
(27°-45°N),withtheaidofoperationalrawinsoundeobservationsat18stationsfortheyearof
1986. Resultsofthestatisticalanalysisrevealedthatthegravitywaveswithverticalwavelengths
of2~Skmaredominantinthelowerstratosphereandtheirdistributioninameridionalplane
along 1400E iscloselyrelatedtothesubtropicaljetoverJapan. Itisalso noteworthythatthis
work proves for the first time the usefulnessofroutine balloon observations for the study of
gravitywaves.
However, recentstudy by Sato (1994) based on 3-yeardata ofthe MU radar claimed that
thegeostrophicadjustmentatthejetaxisisnotnecessarilythemaingeneration mechanismof
gravitywaves,sincemostoftheseinthelowerstratospherepropagatemeridionallytowardthe
jet. Therefore, wehavetosaythattherestillremainsaproblemwiththegenerationprocessof
geostrophicadjustmentaroundthejetstream.
Anotherimportantcandidategravitywavesourceisconvectionassociatedwithsynoptic-scale
disturbances. ByusingtheMUradar,Sato(1993)madeadetailedanalysisofsmall-scaledistur
bancesduringthepassageofatyphoon(tropicalcyclone)overJapanandshowedclearevidence
ofverticallypropagatinggravitywavesinthelowerstratospherewithacharacteristicperiodof
severalhours whichappearedinassociation withthe intense convective motions(rainbands)
inthetyphoon. Itisalsonotedthatherresultrepresentsquitetypicalbehaviourbuttheintense
convection, observedinthetyphoon, is aratherfragmentary phenomenonin theextratropics.
(GravitywavegenerationfromconvectionsinthetropicswillbediscussedbySatointhisvol
ume.)
AstatisticalstudyontroposphericsourcesofgravitywaveexcitationwasalsomadebyFritts
andNastrom(1992)basedondataobtainedaboardcommercialaircraftflyingoverthewestern
partofUSAandeasternPacific. Theirstudyshowedtherelativecontributionofvarioussources
suchastopography,jetstream,frontandconvection.
As was mentionedearlier, the global distribution ofwave sources is, however, quite inho
mogeneous inspace and time, and henceourknowledge ofthe "climatologyofgravity wave
sources"isstillverypoor. Althoughrecentprogressinsatelliteobservations(cf. WuandWaters,
1996)wouldbepromisingforthispurpose,itisemphasizedthatmanymoredetailedobserva
tions,usingvarioustechniquesandcoveringwideregionsoflatitudesandlongitudesandacross
long timespan is ofgreatimportance. In this regards, the use ofa global network ofroutine
balloonobservationsisrecommended.