GEOPHYSICAL
RF•EARCH
LETTERS,
VOL.20,NO.12,PAGES
1259-1262,/UNE
18,1993
COMPARISON
•)FHRDI
WIND
MEASUREMENTS
WITH
RADAR
AND
ROCKET
OBSERVATIONS
M.D.Burrage,
1W.R.Skinner,
1A.R.Marshalift
P.B.Hays,
1R.S.Lieberman,
1S.J.
Franke,
2
D.A.Oell,
1D.A.Ortland,
l Y.T.Morton,
1F.J.Schmidlin,3
R.A.Vincent,
4andD.L.Wul
Abstract.Wind fieldsin the mesosphere
and lower self-absorbed,
whilea stronger
line is usedat higheraltitudes
thermosphere
areobtained
withtheHighResolution
Doppler (85 - 105 kin). For the upwardscan,a line of 'medium
Imager(HRDi) ontheUpperAtmosphere
Research
Satellite
(UARS)by observing
theDopplershiftsof emission
linesin
the 02 Atmospheric
band. The validityof the measured
windsdepends
onanaccurate
knowledge
of thepositions
on
strength'is usedat all altitudes. The wavenumbersand the
relativeline strengthsobservedwith the operationalmode
most commonly used for the mesosphereand lower
thermosphere,which employs two different viewing
the detectorof the observedlines in the absenceof a wind
azimuths, are indicated in Table 1. The use of two lines at
inducedDopplershift Thesepositions
havebeendetermined eachaltitudeallowsthe temperatureand volumeemission
toanaccuracy
ofapproximately
5 ms-1fromthecomparisonrate to be determinedfrom the ratio of the line strengths.
of windsmeasured
by HRDI withthoseobtained
byMF Becauseof the large changein the spacecraftvelocity and
radars. Excellent agreementis found between HRDI
Earthrotationcomponent
of the Doppler shift betweenthe
measuredwinds andwindsobservedwith radarsandrockets. two azimuths,
it wasnotpossiblefor the weakintensitycase
In addition,
thesensitivity
of HRDI to migrating
tidesand to find a singleline thatfell withinthe detectorrangefor both
otherlargescalewavesis demonstrated.
viewingdirections.
The HRDI instrumentincorporatesa fully gimbaled
1. Introduction
telescope,which collectslight from the atmosphereand
The High ResolutionDopplerImager(HRDI) on the allowslimb scansto be performedat any azimuth. Vector
UpperAtmosphere
Research
Satellite
(UARS)is designed
to winds are determinedby observingthe same atmospheric
measurehorizontalwindsin the mesosphere
and lower volumefromtwo nearlyorthogonalviewing directions.This
thermosphere
andin thestratosphere.
Oneof theobjectives is achievedby employingthe pointing capabilityof the
of theHRDI investigations
is to develop
a comprehensivetelescopeandthespacecraftmotion. Usually,the telescope
a regionof theatmosphere
in a directionor azimuth
globalclimatology
of thewindsin thealtituderange65-105 observes
km. This will serveasa referencepointfor futurestudies angleof 45' to thespacecraft
velocityvector,and9 minutes
andprovidecomparison
for globalmodels.To date,most later nearly the same atmosphericvolume is sampledby
studiesof this region have employedthe view of the using a telescopeazimuth of 135'. On a given day,
circulation based on COSPAR
International Reference
Atmosphere(CIRA) data obtainedfrom meteorological
rocketspriorto 1970. Morerecentwindobservations
earfled
outwitha networkof radarsshowfeatures
notpresent
in the
CIRA climatology [e.g. Balsley and Riddle, 1984;
Tetenbaum
et al., 1986;Mansonet al., 1987]. Thisreport
oufiinesthe procedureby which systematicerrorsin the
HRDI dataareinferred,anddemonstrates
theconsistency
of
HRDI
wind
measurements
with
other
observationsare carried out on only one side of the
spacecraft,
eitherthe warm (sun) side or the cold side, and
this determinesthe latitudinalcoverageof the data. The
Doppler shift measuredby the instrumentis a weighted
averageof thevelocitycomponent
at eachaltitudealongthe
line of sight(LOS). ?rofilesof the LOS velocitymustbe
mathematically
invertedusingtheknownweightingfunctions
observational
techniquesand the applicabilityof HRDI observations
to
studies
of largescalemesosphedc
waves.
HRDI is a tripleetalonFabry-PerotInterferometer
[Hays
et al., 1993], which is usedto observethe very smallwind
induced
Dopplershiftsof absorotion
andemission
rotational
to obtain the actual wind.
The inversion of HRDI
data is
carriedoutusinga sequential
estimation
technique
basedon
the methodof Rodgers[!976; !990]. An effect of the
inversion processis that real vertical and horizontal
variationsmay be smoothed,
while any systematicerrorin
the LOS measurement will be distorted.
The LOS wind is derived from the measured eentroid
lines
inthe02Atmospheric
(b
[Abreu
position,vm, of an absorption
or emission!inc on the
k' Zg -X Z-•
! bands
, , et
al.,1989].
Inthemesosphere
andlower
tl•ermosphere,
A (0 detector,andis givenby
- 0) bandemissionfeaturesare observed,the brightness
and
v = vm- Vo(v,q•)- ct(T- T o)- f(t)
self-absorption
of whicharedependent
ontherotational
line
quantumnumberL Lower J valuedlines are typically
brighterbutsufferfrommoreself-absorption,
andthechoice
T•
of whichline to usedepends
on altitude.As theatmosphere
is penetrated
moredeeply,a balancemustbestruckbetween whereall of the termsin Eq. (1) have velocityunits. The
line brightness
andself-absorption.Therefore,in orderto
termv0 corresponds
to the zerowind reference
position,
-v•cosecos(•2xR•
sin
•cos0
scantheatmosphere
from65 to 105kin,rotational
linesof whichis a functionof the wavenumber,v, andthe azimuthof
threedifferent
strengths
areused.Thescanis performed
in
the observation,
•. The parametertt denotesthe sensitivity
bothanupwardanda downward
direction
at approximately of the line position to the mean temperature of the
the samegeographical
location.Measurements
collected instrument,T, relative to a referencetemperature,TO. The
duringthedownward
scanat loweraltitudes
(65 - 85 kin) long term drift of the instrumentarisingfrom the gradual
employa lineof weakerintensity
thatis notsignificantly adjustmentto the space environment (outgassing)is
represented
by a functionof time,f(0. The termse• andf(t)
are obtainedusingobservations
of spectrallinesof onboard
1Space
Physics
Research
Laboratory,
University
ofMichigan,
2Department
ofElectrical
andComputer
Engineering,
University calibrationlamps. Thesecalibrationsare cardedout every
day, and the derived temperatureand long term drift
of Illinois
corrections
areaccurate
to withina few ms-1 (Skinneret al.,
Goddard
Space
FlightCenter,
Wallops
Flight
Facility.
Wind Measurements
with The High Resolution
Department
ofPhysics
andMathPhysics,
University
otAddaide Atmospheric
DopplerImager(HRDI), 1993). The final twotermsof Eq.
(1) are corrections
whichmustbe appliedto accountfor the
spacecraft
velocity,Vs,andtheEarthrotation,whereœis the
elevationangleof theobservation,RE andTE aretheradius
androtationperiodof theEarth,andOand• arethelatitude
andobservation
bearinganglefromnorth.
,
Copyright
1993bytheAmerican
Geophysical
Union.
Papernumber93GL01108
An accurate knowledge of the component of the
0094-8534/93/93 GL-01108503.00
spacecraft
velocityand the Earth rotationin the viewing
!259
TABLE
1.
Azimuth 45'
Ak (km)
65-85
Upscan
13076.318
Downscan
13052.316'
(medium)
85-105
FWARM • /
Wavenumbersand relative strengthsof emission
linesemployedby theHRDI mesosphem
andlower
thermosphcm
scanningmode.
13076.318
(weak)
13138.194
(medium)
Azimuth 135'
Up scan
13076.318
(medium)
13076.318
(strong). (medium).
Downscan
13041.118
(weak)
13138.194
(strong).....
iili•
directionis essential.The spacecraft
velocityis about7500
ms-1, so evena smalluncompensated
component
will
seriouslyaffect the wind determination. The uncertaintyin
therequiredcorrectionlies not in the accuracyof thesatellite
velocity,whichis knownto betterthan 1 ms'l, but in the
locationof the telescopeviewing directionrelativeto the
satellitetrajectory.The spacecraftattitudeis knownto about
0.01', which translatesto a wind measurement
errorof only
BCOLD
Fig. 1. Schematic
diagramillustrating
thegeometry
of HRDI
observationsmade on both the warm and the cold sidesof the
spacecraft.The measurements
FWARMandFCOLD
are
obtained in the forward directions relative to the satellite
~1 ms-1. However,therelationship
between
thespacecraft trajectoryat azimuthsof 45øand-45ø,and the measurements
andBcot.i)areobtained
in thebackward
directions
at
referenceframeandthe telescopeframeexhibitsa variation BWARM
azimuths of 135 ø and -135'.
which dependsmainly on long term changesin the solar
heatingof the spacecraft. The misalignmentbetweenthe
spacecraft
frameandthe HRDI instrumentframeis measured estimatesof the zeroreferencepositionsobtainedfrom HRDI
periodically
by observing
starsof knownposition,
andl,ields
a correction to the measured winds of the order of 5 ms q.
atmospheric
dataaccurate
towithinabout10ms-1.
3. Comparisons
Of Wind Observations
2. Zero Wind Position
Becauseof the large Doppler shifts inducedby the
spacecraft,which has the effect of moving the spectrum
around on the detector, and because of slight non-
uniformities
in the detectorresponse,
it wasnotpracticalto
try tolocatethezerowindreference
position,
v0, duringprelaunch calibration. Instead, it is determined using
atmospheric
winddatacollectedin orbitin conjunction
with
dynamical assumptions, and employing correlative
measurements
made by rocketsand radars. The zero wind
positiondepends
only on wavelengthandtelescope
azimuth,
andwasdetermined
to a first orderof accuracyusinga two
stepprocedure
whichemploysdynamicalassumptions.
The
first stepassumes
that the globalmeanwindssampledat
aboutthesamelocaltimedonotchangerapidlyovera period
of a day or two. By alternatingthe observations
from the
Further improvement in the accuracy of the zero
referencepositionsrequires the comparisonof HRDI
measurements
with groundbasedinstruments(!idars,radars,
etc.), specialin situ measurements(balloons,rockets),and
the resultsof models and climatology. The problems
encountered in comparing satellite remote sensing
observations
with othertypesof datahavebeendiscussed
by
Gille et al. [1984]. Correlativeinstruments
generallyprovide
vertical profiles more or less directly above the station,
yieldingessentiallypoint measurements.In contrast,limb
viewingsatelliteinstruments
suchas HRDI give profiles
which are a weightedaveragealong the line of sight.
Anotherdifficulty is that the coincidenceof the HRDI and
correlativemeasurement
is neverexact,eitherin spaceor
time.
There are also uncertainties
associated with the
warm side (azimuths -45 ø and -135') to the cold side
averaging
procedures
employedby thedifferentmeasurement
techniques.For example,MF radarsmayindicatevariations
(•_imuths45ø and 135ø) for two consecutivedays, it is
in thewindfielddueto insufficient
sampling
of shortperiod
gravitywaves[e.g.Lloyd et al., 1990]. By contrast,
HRDI
possibleto obtaininformationon the zero referencesfor the
hasan effectivehorizontalresolutionof a few hundredkin,
and therefore does not readily detect such waves.
Consequently, a series of consecutive radar wind
measurements
collected
with thetypical5 minuteintegration
geometry
is illustrated
in Figure1. Theforwardviewingline
position measurements
FW^RMand Fcot.D, which are periodmayexhibitsignificantvariability,asis illustratedin
madewith the UrbanaMF
correctedfor the temporalandthermaldriftsandspacecraft Figure2 by a set of observations
radar. The closestHRDI profile, which was obtained
and Earth rotationvelocities,incorporatethe samezero
referenceposition,Vro,while the backwardmeasurements approximately100 km from the radar,is alsoincludedin the
figure. In orderto providea bettercomparison
with HRD!,
BWARM
andBCOLD
eachincludethereference
value,Vso.If
an attemptis made to remove the effect of small horizontal
the components
of the wind at azimuths-45' and 135ø are
structures
in theradardataby averaging
overa timeperiodof
U.45andU135,respectively,
then
differentazimuthssincethe components
of the wind in the
45' and -135' (or-45 ø and 135ø) directionsshouldbe of
approximatelyequal magnitudebut oppositesign. This
Fw•a•t= U.,5 - vF0
(2)
usually1-2 hours.Because
of thedifferenteffectivespatial
and temporal resolutions of the HRDI and correlative
measurements
andthehighdegreeof shorttermatmospheric
and
Bcou)= U•35- vB0
(3)
If thewindfielddoesnotchange
significantly
duringthe
two days taken to collect the warm side and cold side
measuremenu,
andthedatai.saveraged
overeachdayfor a
givenlatitude,
thenU4s= -U•35,andthus
Fw•am
+ Boo
u)=-(vF0+ vB0)
(4)
Thedetermination
of theabsolute
valuesof VF0andvB0
requiresa secondstepwhichusesthe assumption
thatthe
long-term mean meridional winds are zero. This method
employsdatasampled
symmetrically
abouttheequatorin
ordertoremove
tidaleffectsandaveraged
overa longperiod
to reduceseasonal
variations.Sincethe recoveryof any
component
of thewindrequiresbothviewingdirections,
the
secondstageof the procedurealso yieldsan expression
involvingbothVFoandV•o. However,theymaybeseparated
by substituting
for eitheroneof themusingtheinfomarion
obtained
fromthefirststep[Eq. (4)]. Thisprocedure
yields
variability,the twotechniques
arenotreallysampling
the
same quantity. In addition, most observationalmethods
(includingHRDI) employfilteringtechniques
whichare
designedto removethe effects of measurement
noise. It is
possiblethat highfrequencycomponents
that are actually
present
in thewindprofilemayberemovedaswell.
Any differences between HRDI
data and other
measurements
resultingfrom the problemsdescribedabove
would be random,and thereforestatisticalcomparisons
shouldrevealthe systematic
errors. Oneapproach
is to
determine the mean differences between the HRDI and
correlative measurementsand the standard deviation of the
meandifferences
foreachsiteusingasmanycoincidences
as
possible
(typically10-50). Windcomparisons
arecarried
out
by first transformingthe correlativezonal and meridional
measurementcomponentsto the correspondingHRDI
viewing direction. Consistentoffsetsbetweenthe wind
observedby HRDI and that obtainedusing other
measurement
techniques
havealreadyindicatederrorsin the
initialdetermination
of theHRDI zeroreference
positions.
Quantifying
the errorsfrom thiskind of comparison
is
11o
110
lOO
100
,,
11o
,
,,,
11o
lOO
1 oo
:
.
:
.
.
,• :,:
•
80
•
8o
8oi
-
.
iI--e--t
:
:
:
i
7O
7O
:,--.--,
.
70-
:::
:
--
radar
,
-150
,
-
I
i
t
60
:
t
I
,
,
0
ZONALWIND (M/S)
60
150
1
6O
o
50
MERIDIONAL
WIND(M/S)
-'0
-5
0
5
10
FORWARDVIEWWIND(M/S)
60
-10
i
-5
0
ii i m
5
10
BACKWARDVIEW WIND (M/S)
Fig.2. Seriesof 5 minute
integration
windprofiles
obtained Fig. 3. Mean differencesbetweenHRDI and Urbana MF
by the Urbana MF radar between !6:!3 and 17:13 UT on
December25, 1991. The HRDI windmeasurements,
which
were made 113 km from the radarsite at 16:43UT, are
includedfor comparison.
radarwindsresolvedinto (a) the HRDI forwardviewing
direction(azimuth45ø) and (b) the backwardviewing
direction(azimuth 135ø). The error bars denote standard
deviations of the means.
difficultsincetheoffsetis incorporated
intothelineof sight oscillations is much smaller than that for the weaker
measurements,
whicharetheninvertedusingthesequential constraintof the previousfigure, greatly improving the
estimation
technique
to yieldthewindprofile.Theinversion agreement
with the rocketobservations.This suggests
that
process tends to distort systematicerrors in the LOS
measurements. In addition, the variousemissionlines which
muchof the verticalstructurein the HRDI windsof Figure
4(a) is due to measurementnoise.
contribute
to thefinalHRDI windproduct
mayhavedifferent
The determination
of thezeroreferencepositionsandthe
offseterrors.An examination
of theLOS windprofileasa
appropriate
degreeof smoothing
to applyto the HRDI wind
functionof wavelengthis necessary
to isolateandquantify measurementshas yielded results which are in very good
agreementwith rocketsandwith MF radars. Figure5 shows
thedifferenteffects.Linepositionoffseterrorsdetermined
in
this way are usedto correctthe HRDI database.To date,the
a comparison
of the meridionalwind profilesmeasuredby
zero referencepositionsof all of the lines listedin Table !
HRDI andby the Urbanaradaron 12 consecutive
days. For
have been adjustedto obtain the bestagreementbetween eachof theprofiles,theHRDI measurement
was carriedout
within 300 km of the radar site. The local time of each
HRDI and MF radarslocatedat Urbana(40.2øN, 271.8øE)
variedby about20 minutesper day, due to the
(Franke and Thorsen,Mean winds and fidesin the upper coincidence
of the UARS orbit, and all of the observations
middle atmosphereat Urbana(40' N, 88øW) during1991- precession
1992,submitted
to I. Geophys.Res.,1993),Christmas
Island presented
in Figure5 wereobtainedfor the localtime range
(2.0' N, 202.6' E) [Vincent and Lesicar,1991] andAdelaide 10:30-13:30. Clearly,the two techniques
resolvethe same
(34.6øS, 138.5øE) [VincentandFdtts, 1987].
verticalstructures,
andin generaltheseappearto be tidal in
The agreement
of themeanwindsobserved
by HRDI and nature. In particular,the winds observedon December20
of-25 kin, consistent
with the
by the UrbanaMF radar after adjustingthe zero reference exhibita verticalwavelength
valuesis illustratedin Figure3 for boththe forwardandthe (1,1) diurnal tide, and there is some suggestionof a
of theoscillationon subsequent
days.
backwardHRDI viewingdirections.Thefigureindicates
the downwardprogression
Obviouslyother phenomena,such as the semidiurnalfide,
non-migratingtides and planetary waves, must also be
to the observedwinds,particularlyon the earlier
the mean differences. The results were obtained using contributing
approximately
40 coincidences
with theUrbanaradarwhich daysshownin the figure. For example,the shortervertical
wavelengthof !0-15 km seenon December15 and 16 is
occurred between December, 1991 and December, 1992.
The radar data was averagedover periodsof two hours, perhapssuggestiveof a non-migratingtidal component.
When thisstudyis extendedto the globalview of the wind
centeredon the time of the closestapproachof the HRDI
by HRDI andincorporates
measurements
from
observation
tangentpointto theradarstation.The maximum fieldprovided
spatialdisplacement
of thetwo measurements
was500 kin, networksof radarsandotherlocalizedtechniques,it should
and since the effective horizontal resolution of HRDI is of the
bepossible
to assess
thedifferentcontributions
of thevarious
samemagnitude,
in theaveraging
process
coincidences
were dynamicalcomponents.
mean differencesin the wind measurement
madeby the two
techniquesandthe errorbarsdenotestandard
deviations
of
notweightedaccording
to theseparation
distance
butonlyto
theHRDI measurement
variance.Figure3 indicates
thatthe
differences
betweenthetwo techniques
varyaboutzerofor
4. Conclusion
The validity of HRDI measuredwinds relies on an
accurate
knowledge
of thezerowindpositions,
theeffectsof
Comparisons
with correlative
datasetsalsoprovide thermalandtemporaldriftsandthe LOS componentof the
valuable information on the level of constraintwhich should spacecraft
velocityandEarthrotation. The instrumental
be employed
by thesequential
estimator
usedto invertthe driftsarequantifiedby monitoringthe stabilityof onboard
HRDI observations.
Thisparameter
controls
thedegree
of calibrationlines, and the spacecraftvelocity and Earth
bothviewing
directions,
anddonotexceed
5 ms'1 atany
aidrude.
horizontal
smoothing
of the recovered
windprofile. An rotation corrections are determined by measuring the
example
of a comparison
between
HRDIwindsgeneratedinstrument/spacecraft misalignments using HRDI
usingtwodifferent
levelsof smoothing
withthose
obtained observations of stars. The absolute values of the reference
areestimated
by applyingappropriate
dynamical
bya rocket
ispresented
inFigure
4. FortheHRDIresults
in positions
Figure4(a),thesequential
estimator
employed
a relatively constraints to mean HRDI atmospheric observations.
weak constraintwhich effectivelyaverageshorizontal increasedconfidencein the HRDi wind retrievalsis gained
structures
of scalesizelessthan500 kin. The largevertical
by employing
comparisons
with correlative
measurements.
onlyto establish
thevalidityof the
variations
apparent
intheHRDIwinds
arenotsupported
by Thisactivityservesnot
but alsoprovidesa commonbaseline
therocket
data.Figure
4(b)demonstrates
theeffect
ofusing HRDI measurements,
a stronger
constraint,
equivalent
toremoving
structures
of whichcanbe usedto intercomparethe manyground-based
techniques.
In addition,theuniquespatialand
scalesizelessthan1000kin. Theamplitude
of thevertical observational
120
'
i
HRDI
,
--
120
,
I
Rocket
•.•
11o
HRDI
--
Rocket
,•
,,,,
.
,
,
,
I
i
[
I
!
I
I
Dec1
,,
,
'
'
I
I
•• 90
.:i
so
110
I.-;
...
lOO
9o
<
8o
r•
h,
•" ::l
60
I,
,
I
•00[
' ' •ec
•
9O
70
8O
7o
ß
< 70
/ .,,radar
•.. 100
r•
6ec1
lOO
7O
t
I
_
ß
.
'
'
6ec2
!
i
ec2
.... , , ,
80
,
-150
0
1
-150
ZONAL WIND (M/S)
0
150
70
MERIDIONALWIND (M/S)
Dec 25
120
120
•
HRDI
--
Rocket
•
110
HRDI
--
Rocket
110
70
-50
.-. 100
•
9O
0
50
V (M/S}
,•o
o
•o
v (M/S)
-50
0
50
V (M/S)
Fig. 5. Comparisonof meridional (V) wind profiles
measuredby HRDI (solid lines) and the Urbana MF radar
(brokenlines) on 12 consecutive
daysfrom December14 to
D
90
<
80
December 25, 1992.
70
7O
6O
50
0
150
ZONAL WIND (M/S)
-150
0
150
MERIDIONAL WIND (M/S)
Fig. 4. Windprofilesdetermined
usingHRD! at 16:09UT
anda rocketlaunchedfrom WallopsIslandat 16:14UT on
March25, 1992. The spatialseparation
betweenthe twosets
Hays, P. B., V. J. Abreu, M. E. Dobbs, D. A. Gell, H. J.
Grass!,andW. R. Skinner,The High ResolutionDoppler
Imager on the Upper AtmosphereResearchSatellite,J.
Geophys.
Res.,in press,1993.
Lloyd, N., A. H. Manson,D. J. McEwen, and C. E. Meek, A
comparison of middle atmospheric dynamics at
Saskatoon(52'N, 107øW) as measuredby a medium
frequencyradar and a Fabry-Perotinterferometer,J.
Geophys.
Res.,95, 7653-7660,1990.
Manson,A. H., C. E. Meek, M. Massebeuf,J. L. Fellous, W.
of measurementswas about 300 kin, and the solar zenith
G. Elford, R. A. Vincent,R. L. Craig, R. G. Roper,S.
Avery, B. B. Balsley, G. J. Fraser,M. J. Smith, R. R.
Clark, S. Karo,andT. Tsuda,Mean windsof the upper
the line of sightobservations
with the sequential
estimator
middleatmosphere
(.-70-100km) from the globalradar
employinga constraint
whicheffectivelyaverages
horizontal
network:comparisons
with CIRA 72, andnewrocketand
structuresof (a) scalesize lessthan 500 km, and (b) scale
size less than 1000 kin.
satellitedata,Adv.SpaceRes., 7, 143-153,1987.
Rodgers,C. D., Retrieval of atmospherictemperatureand
compositionfrom remote measurementsof thermal
temporalcoverageof the HRDI databasewill facilitatethe
radiation,Rev.Geophys.and SpacePhys.,14, 609-624,
first effective observationaltest of the accuracyof global
1976.
dynamicalmodels. Also, greatprogresswill be madewith
Rodgers,
C. D., Characterizationand error analysis of
studiesof mesospheric
dynamicsby meansof a synthesis
of
profilesretrievedfromremotesoundingmeasurements,
J.
HRDI observations
and localized(groundbasedand in situ)
measurements. HRD! measurements are fixed in local time
Geophys.
Res.,95, 5587-5595,1990.
for a givenday,buthavecompletelongitudecoveragewhich Tetenbaum,D., S. K. Avery, andA. C. Riddle,Observations
of meanwindsandtidesin theuppermesosphere
during
providesimportantinformationon non-migratingtidesand
1980- 1984,usingthePokerFlat, AlaskaMST radarasa
planetarywaves, while localizedtechniquesare fixed in
meteorradar.J. Geophys.
Res.,91, 14,539-14,556,1986.
longitude,but cover a rangeof local timesgiving a better
Vincent, R. A., andD.C. Fritts, A climatologyof gravity
view of themigratingcomponents.
wavemotionsin themesosphere
at Adelaide,Australia,J.
Amos. $ci., 44, 748-760, 1987.
Acknowledgments:This work is sponsored
by NASA
Vincent,R. A., andD. Lesicar,Dynamicsof the equatorial
throughContractNo. NAS 5-27751.
mesosphere:
First resultswith a new generationpartial
anglewas40ø. The HRDI windsweregenerated
by inverting
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(Received
February1, 1993;
revisedApril 16, 1993;
acceptedApril 20, 1993.)