Global-scale tidal structure in the mesosphere and lower thermosphere during the PSMOS campaign of...

Journal of Atmospheric and Solar-Terrestrial Physics 64 (2002) 1011–1035www.elsevier.com/locate/jastp

Global-scale tidal structure in the mesosphere and lowerthermosphere during the PSMOS campaign of June–August

1999 and comparisons with the global-scalewave model

D. Panchevaa ; ∗ N.J. Mitchella, M.E. Haganb, A.H. Mansonc, C.E. Meekc, Yi Luoc,Ch. Jacobid, D. K7urschnere, R.R. Clarkf , W.K. Hockingg, J. MacDougallg,

G.O.L. Jonesh, R.A. Vincenti, I.M. Reidi, W. Singerj, K. Igarashik, G.I. Fraserl,T. Nakamuram, T. Tsudam, Yu. Portnyaginn, E. Merzlyakovn, A.N. Fahrutdinovao,

A.M. Stepanovo, L.M.G. Poolep, S.B. Malingap, B.L. Kashcheyevq, A.N. Oleynikovq,D.M. Rigginr

aDepartment of Physics, University of Wales, Aberystwyth, Ceredigion SY23 3BZ, UKbHigh Altitude Observatory, NCAR, Boulder, CO, USA

cInstitute of Space and Atmospheric Studies, University of Saskatchewan, Saskatoon, CanadadInstitute for Meteorology, University of Leipzig, Leipzig, Germany

eInstitute for Geophysics and Geology, University of Leipzig, Collm Observatory, GermanyfUniversity of New Hampshire, Durham, USA

gUniversity of Western Ontario, London, CanadahBritish Antarctic Survey, NERC, Cambridge, UK

iUniversity of Adelaide, Adelaide, AustraliajAlbinos-Institute of Atmospheric Physics, K0uhlungsborn, GermanykCommunications Research Laboratory, Koganei, Tokyo, Japan

lUniversity of Canterbury, Christchurch, New ZealandmRadio Science Centre for Space and Atmosphere, Kyoto, Japan

nInstitute for Experimental Meteorology, Obninsk, RussiaoKazan State University, Kazan, Russia

pRhodes University, Grahamstown, South AfricaqKharkov State Technical University of Radioelectronics, Kharkov, Ukraine

rColorado Research Associates, Boulder, CO, USA

Abstract

Observations of mean winds and semidiurnal and diurnal tides in the mesosphere=lower-thermosphere (MLT) region weremade during the 3-month Planetary-Scale Mesopause Observing System Summer 1999 campaign. Data from 22 ground-basedradars (and from two other instruments with measurements for the same period but in 1998) allow us to investigate the abilityof the GSWM-00 to simulate the solar tides in the mesopause region (90–95 km). Here we have found that the GSWM-00provides an increasingly reasonable estimate of most of the tidal characteristics in the MLT region. However, the representationof the 24 h tide appears superior to that of the 12 h tide. Some of these discrepancies are studied in detail. In particular, theobservations reveal signiAcant 12 h tidal amplitudes at high latitudes in the Northern Hemisphere summer. There is evidencefor relation between the longitudinal variability of the mean zonal wind and the tidal characteristics seen from the radar wind

∗Corresponding author. Tel.: +44-1970-621902; fax: +44-1970-622826.E-mail address: [email protected] (D. Pancheva).

1364-6826/02/$ - see front matter c© 2002 Elsevier Science Ltd. All rights reserved.PII: S1364 -6826(02)00054 -8

1012 D. Pancheva et al. / Journal of Atmospheric and Solar-Terrestrial Physics 64 (2002) 1011–1035

measurements in the summer middle latitudes and a quasi-stationary planetary wave with zonal wave number one. c© 2002Elsevier Science Ltd. All rights reserved.

Keywords: MLT dynamics; Wind and tidal observations; Models

1. Introduction

The Planetary-Scale Mesopause Observing System(PSMOS) is one of four international initiatives insolar-terrestrial physics conducted during the period 1998–2002 under the auspices of the ScientiAc Committee onSolar-Terrestrial Physics (SCOSTEP). PSMOS is designedto extend our understanding of the dynamical processes inthe mesosphere=lower-thermosphere (MLT) region, partic-ularly in relation to the variability of winds, waves, tidesand atmospheric structure, to long-term trends. A furtherimportant element is the improvement of models.

PSMOS has established a co-operative network of variousground-based instruments spanning the planet from Arcticto Antarctic latitudes, albeit with some irregularity in latitu-dinal and longitudinal coverage. Co-ordinated studies by theinstruments of such networks are capable of investigatingtides and planetary waves on a planetary scale. The PSMOSnetwork of radars conducted an observational campaign inthe period June 1–August 31, 1999 as the cornerstone ofPSMOS Project 1, the Global-scale tidal variability exper-iment. The three major scientiAc objectives of this experi-ment were: (1) Characterising, and distinguishing betweenthe temporal and spatial variability of tides. (2) Mappingthe latitudinal and longitudinal structure of measured tides.(3) Investigating the role of planetary-wave=tidal interac-tions in tidal variability. Here we present results arising fromthe Arst two of these objectives.

Characterising the global-scale structures of MLT-regiontides (and planetary waves) has also been a focus of a num-ber of earlier international programmes, such as the MiddleAtmosphere Program (MAP) and the Middle AtmosphereCo-operation (MAC), the Solar-Terrestrial Energy Pro-gramme (STEP) and one of its component parts, the Meso-sphere Lower Thermosphere Coupling Study (MLTCS).As part of the latter, a series of global 10-day observationalcampaigns were conducted to investigate the role of tidesand planetary waves in MLT coupling. One of the largestregional programmes, but with a strong global dimension,is the US programme on Coupling, Energetics and Dynam-ics of Atmospheric Regions (CEDAR). In part, its goal isto obtain a better understanding of the processes couplingthe mesosphere to the thermosphere. In the framework ofCEDAR, more than 17 campaigns of 4 or more days havebeen conducted over the past decade. Illustrative resultsfrom these co-ordinated large-scale campaigns have beenreported by, for example, Forbes and Salah (1991), Man-son et al. (1990, 1991), Salah et al. (1994), Hagan andSalah (1995), Deng et al. (1997) and Palo et al. (1997).

The Dynamics Adapted Networks (DYANA) project con-ducted a rather longer campaign of 2 months duration inthe interval January 15–March 15, 1990. In this campaign,co-ordinated ground-based radar measurements of windsand tides in the MLT region were carried out at 14 diJerentlocations in the mid-latitude Northern hemisphere, but withlongitudes that ranged from 107◦W to 102◦E (Singer et al.,1994; Portnyagin et al., 1994).

The 3-month PSMOS campaign of summer 1999 is themost extensive of such campaign conducted to date, in termsof duration and the number of participating ground-basedradars. During the campaign, 22 ground-based meteor, MFand other radars distributed around the globe providedmeasurements of the horizontal wind Aeld in the MLTregion. In this paper we compare the observations of diur-nal and semidiurnal tides made by this network of radarswith the climatological predictions of the last version ofthe Global-Scale Wave Model, the so-called GSWM-00(Hagan et al., 2001). This is the Arst global-scale compari-son of the tides modelled in GSWM-00 with ground-basedobservational data in the height range 90–95 km.

The main focus of this paper is thus to establish themonthly-mean, latitudinal and longitudinal structures of themean zonal wind, and of the monthly-mean tidal amplitudesand phases as revealed during June–August of 1999, and tocompare these observations with the GSWM-00. Because ofthe use of data from several meteor radars operating with-out height resolution, we will only consider heights in therange 90–95 km. The global-scale, intra-seasonal, variabil-ity of the tides and their coupling to planetary waves willbe presented in a subsequent paper.

2. Observations and analysis of the radar data

The data analysed and presented here were recorded by22 ground-based systems, most of which are either meteorwind radars (MWR) or medium frequency radars (MFR), al-though some data were also provided by low-frequency (LF)D1 ionospheric drift measurements and imaging Doppler in-terferometers (IDI). Table 1 lists the locations of the variousinstruments used and presents some notes on the data ob-tained. Fig. 1 indicates the geographic locations of the var-ious ground-based instruments. However, because we arehere primarily interested in the climatological structure ofthe tides, occasional data from other years, particularly forlatitudes poorly covered by the available instruments, willalso be included without serious detriment to the study. In

D. Pancheva et al. / Journal of Atmospheric and Solar-Terrestrial Physics 64 (2002) 1011–1035 1013

Table 1

Station Instrument Location Height (km) Period of Measurements

Resolute Bay, Canada Meteor radar 75◦N, 95◦W 94 01 June–31 JulyAndenes, Norway MF radar 69◦N, 19◦E 90 and 94 01 June–31 AugustESRANGE, Sweden Meteor radar 68◦N, 21◦E 90 and 94 05–26 AugustKazan, Russia Meteor radar 56◦N, 49◦E 90 and 94 25 June–31 AugustJuliusruh, Germany MF radar 55◦N, 13◦E 89 and 95 01 June–31 AugustObninsk, Russia Meteor radar 55◦N, 37◦E No height 01 July–31 August

resolutionSaskatoon, Canada MF radar 52◦N 107◦W 91 and 94 01 June–31 AugustCollm, Germany LF D1 method 52◦N, 15◦E about 95 01 June–31 AugustCastle Eaton, UK Meteor radar 52◦N, 2◦W No height 01 June–31 August

resolutionKharkov, Ukraine Meteor radara 50◦N, 36◦E 90 and 96 01 July–31 AugustWakkanai, Japan MF radar 45◦N, 142◦E 90 and 94 01 June–20 AugustLondon Ontario, MF radar Meteor radar 43◦N, 81◦W 91 and 94 01 June-19 AugustCanada 93Durham, USA Meteor radar 43◦N, 71◦W 95 01 June–31 AugustNew Mexico, USA Meteor radar 35◦N, 107◦W 93 1–30 JuneYamagawa, Japan MF radar 31◦N, 131◦E 90 and 94 01 June–31 AugustJakarta, Indonesia Meteor radar 6◦S, 109◦E 90 and 95 01 June–10 AugustGrahamstown, South Meteor radar 33◦S, 26◦E No height 01 June–31 AugustAfrica

resolutionAdelaide, Australia MF radar 35◦S, 138◦E 90 and 94 01 June–31 AugustChristchurch, New MF radar 44◦S, 173◦E 90 and 95 01 June–31 AugustZealandDavis, Antarctica MF radar 68◦S, 78◦E 90 and 94 01 June–31 AugustHalley, Antarctica Imaging Doppler Interferometer 75◦S, 26◦W 92 01 June–31 August

aOnly zonal wind component.

particular, wind data measured by MFR at Rothera (67◦S,68◦W) during June–August 1998 will be considered so as toexpand the data base of high-latitude Southern Hemisphereobservations. Similarly, measurements of ion velocities inthe lower thermosphere made during August 1998 by theEISCAT Svalbard Radar (ESR) (78◦N, 16◦E) will be usedwhen considering the high latitudes of the Northern Hemi-sphere (Van Eyken et al., 2000).

In comparing observations made by diJerent types of in-struments with model predictions it is important to be awareof the limitations and diLculties inherent in each observa-tional technique, as well as any limitations inherent in themodel. Measurements of MLT-region winds made by MFRand MWR have been widely described in the literature (e.g.,Kingsley et al., 1978; Roper, 1984; Manson andMeek, 1986;Tsuda et al., 1987; Vincent and Lesicar, 1991; Portnyaginet al., 1994). Hocking and Thayaparan (1997) reported avery thorough comparison between winds and tides in theMLT region at mid-latitudes measured by the MFR andMWR techniques. The authors concluded that, in general,both methods provide reliable means in synoptic studies ofmotions in the height range 85–94 km at tidal periods andbeyond, although the phases of the tides agree rather betterthan the measured tidal amplitudes. Cervera and Reid (1995)presented a comparison of wind velocities at heights 80 and

98 km measured by the colocated MWR and MFR duringthe interval from September 10 to 20, 1993. The agreementbetween the two techniques was good below 90 km, whileabove 90 km they found that the MFR yields smaller windspeeds than the MWR.

The Arecibo Initiative in Dynamics of the Atmo-sphere (AIDA) ’89 was a multi-instrument campaign de-signed to compare various mesospheric wind measurementtechniques. Comparisons between the operating in thiscampaign MWR and incoherent scatter radar (ISR) arepresented by Djuth and Elder (1993). General agreementwas found between the two techniques, however they foundsmall systematic diJerences above 88 km in some of theirresults. Turck et al. (1995) studied the comparison of theISR measurements with those of a 3:175 MHz MF=HF radaroperating as an IDI during this campaign. They have com-piled 208 proAles which showed that the prevailing windand diurnal and semidiurnal tides deduced from the IDI dataprovide a background wind about which both the IDI andISR winds are normally distributed over the height rangefrom 70 to 97 km. Hines et al. (1993) conducted intercom-parisons among wind measurements using MF=HF-IDI,ISR and MWR during the AIDA’89 campaign with thefundamental objective of testing the wind interpretation ofMF=HF ‘partial reOection drift’ measurements in the lower


Fig. 1. A map indicating the geographic locations of the ground-based instruments that participated in the PSMOS campaign.

ionosphere. On the basis of comparisons of diJerent sets ofobservations they concluded that MF=HF system used wascapable of measuring the neutral air motion below 80 km,and above 80 km failed to give consistently reliable neutralwind measurements. We have to point out however, thatthese results were limited to a single site over a limitedperiod (7 days) of observations. The authors suggested thatthe discrepancies might be a result of the contamination ofwind estimates by the phase velocities of the gravity waves.

Lloyd et al. (1990) compared the winds measuredby an optical Fabry–Perot interferometer (FBI) systemoperating at 5578 nm (green line) and by an MFR sys-tem during the autumn and early winter in 1987. Theresults from the two instruments were consistent witheach other, both in wind direction and amplitude. Sim-ilar investigation was later carried out by Phillips etal. (1994), and again, strong similarities in the MFRand FBI Doppler wind Aelds were observed, althoughsome diJerences existed (possible due to auroral con-tamination). Later detailed comparisons have been com-pleted between the winds and waves measured by twoMFRs in the Canadian prairies and FBIs at Saskatoonand Calgary (Manson et al., 1996; Meek et al., 1997).

Particular care has been taken to exclude FBI airglow con-tamination by aurora or scatter from clouds. Statistical com-parisons of hourly mean winds (1988–1992) for the Saska-toon MFR and FBI using scatter plots, wind speed-ratios,and direction-diJerence histograms showed excellentagreement. It was demonstrated by additional modellingthat gravity waves signiAcantly aJect system-comparisonsdue to temporal and spatial averaging. No serious biasesin speeds or directions occur at the height of the bestagreement, 98 km. If anything, the MFR speeds appearbigger.

Recently, much work has been done in comparativestudies between winds observed from the high-resolutionDoppler imager (HRDI) instrument on the upper-atmosphereresearch satellite (UARS) and those obtained from ground-based stations. The comparisons demonstrated that therecan be signiAcant diJerences in the winds obtained by thetwo techniques, most notably between winds measured byMFR above about 85 km and the HRDI winds (e.g. Burrageet al., 1993, 1996; Khattatov et al., 1996; Lieberman et al.,1998). The largest discrepancies were found in the merid-ional wind component. Meek et al. (1997) showed that thewind velocities at heights of best agreement measured by


the MFR at Saskatoon and HRDI are typically larger for thesatellite, as MFR=HRDI= 0:7–0:8. Portnyagin et al. (1999)presented some results of comparison between the lowerthermosphere zonal winds as seen by the ground-basedradars and by the wind-imaging interferometer (WINDII)on board of the UARS satellite. It was shown that theseasonal variations of the zonal wind measured by satelliteand ground-based techniques can be described by the sameannual and semiannual components. However, systematicbias was found for the annual mean zonal winds with theradar winds (MWR and MFR) generally smaller than thoseof WINDII by factor 2–2.5, as this bias is practically inde-pendent of altitude. Possible biases in the radars and withWINDII were discussed, including the notion that calibra-tion of the Doppler velocities in the latter could exist.

In this study we concentrate only on heights between 90and 95 km, having in mind the above-mentioned experimen-tal evidences for possible disagreement in the wind mea-surement by diJerent observational techniques above 85–90 km. This range was chosen for two reasons. Firstly, itavoids the uncertainties in the MFR data caused by possi-ble group-retardation eJects above 95 km, which apply es-pecially in summer (Namboothiri et al., 1993). Secondly,this height is representative of the data measured by thoseMWR systems operating without height Anding, several ofwhich are used in this study.

The D1 method is used to measure horizontal windsover Collm at the reOection height (80–110 km) oflow-frequency (LF) radio waves from commercial radiotransmitters. Data from three measuring paths are combinedto half-hourly mean values at 52◦N, 15◦E. This measure-ment technique is described in detail by K7urschner andSchminder (1986) and Jacobi et al. (1997). Data from theaverage height of 95 km are used in this study. A recentlong-term comparison between Saskatoon MFR and CollmLF D1 wind measurements has shown that the seasonalvariations of both mean winds and tidal amplitudes andphases are similar at both sites, providing conAdence in thereliability of inter-comparisons between these types of data(Jacobi et al., 2000).

The Imaging Doppler Interferometer (IDI) at Halley usesa software adaptation of a digital ionosonde to make obser-vations of the mesosphere at a radio frequency of 2:75 MHz(Jones et al., 1997). The technique uses Doppler sortingto identify and categorise weak partial reOection echoeswhich provide estimates of the background wind with ver-tical and temporal resolution of 5 km and 5 min, respec-tively. Mesospheric winds derived using the IDI techniqueat Halley show the diurnal and seasonal variations expectedfor this location (Charles and Jones, 1999). The winds arealso in agreement with those obtained from near-range, me-teor echoes received by the Halley SUPERDARN HF radar(Jarvis et al., 1999). Although the lack of co-located facili-ties means that a detailed comparison has not yet been pos-sible between this IDI and the more common techniques formeasuring mesospheric winds, results obtained from both

Halley, Antarctica and from Bear Lake, Utah suggest thatthe method is reliable. Berkey et al. (2001) illustrated thispoint using results from IDI implementation at Bear Lakewhere observations were found to be consistent with thosefrom nearby optical instruments.

The ESR made its Arst measurements in 1996, but dur-ing the Arst 2 years of operation reliable measurements inthe lower thermosphere were impossible because of groundclutter (Van Eyken et al., 2000). The Arst observations afterelimination of this problem were carried out in August 1998and the results of these measurements are used for compari-son in this study. The ESR is similar to EISCAT UHF radarat TromsH, but operates at a frequency of 500 MHz. Man-son et al. (1992) compared measurements made by MFRand EISCAT at 70◦N and demonstrated that the tidal ampli-tudes and wind speeds measured by MFR are on the aver-age only 65–70% of those measured by the EISCAT radarand by rockets. The reason for these discrepancies is notyet fully understood, but it should be borne in mind whenconsidering the comparisons made later in this study.

The analysis proceeded by Arst calculating time series ofhourly-mean zonal and meridional winds for each instru-ment. To ensure the most robust inter-comparisons possiblebetween wind and tidal parameters observed by the diJerentinstruments and techniques, a common analysis was thenapplied to the hourly-mean data recorded at each location.This analysis yielded the amplitudes and phases of the 24 hdiurnal tide and the 12 h semidiurnal tide. Note that mostof the radars participating in the campaign were actuallyable to make measurements at two heights in the range 89–96 km (Table 1), and so provided data with at least someinformation on the vertical structure of the winds and tides.

The campaign period purposely covered the summer sea-son in the NH at a time when the quasi-2-day wave can reachlarge amplitudes. To reveal the underlying winds and tides,we have used a best-At model to remove this wave from thetime series. Most of the data presented here were analysedusing a simple linear least-squares Atting algorithm. Thetime series were Atted with a superposition of a mean windand 48-, 24-, 12- and 8 h harmonic components. The datapoints were weighted in the Atting process according to thenumber of individual measurements composing each hourlymean, when such information was available. Otherwise alldata points were equally weighted in the Atting process. Forthose instruments with height resolution each height wastreated separately. The harmonic components were deter-mined in segments of 4-day duration. The segment was thenincremented through the time series in steps of 1 day andthe process repeated, yielding daily-spaced values for themean winds, the quasi-2-day wave and tidal amplitudes andphases. To estimate the conAdence levels we assumed thatthe residual Atting error is described by a Gaussian-whitenoise. The Student’s t-test was then used to estimate theconAdence levels.

Monthly means of the prevailing winds and the ampli-tudes and phases of the various tides were produced in


order to compare with the GSWM-00 model. Monthly-meantidal amplitudes were obtained by taking the arithmeticmeans, while the mean phases were calculated from vec-tor sums. Little diJerence was found between arithmeticand vector-averaged amplitudes although the latter valueswere slightly smaller. All phases were expressed as localtimes of either maximum eastward or northward wind ata given height. The estimated standard deviations for themonthly-means were about 2–4 m=s for tidal amplitudeand 0.3–1:8 h in 12 h tidal phase and 0.5–3 h in 24 h tidalphase. Larger phase errors resulted when the amplitudeswere small. Monthly-mean tidal characteristics were notcalculated for a particular site if the available data had atotal duration of less than half a month.

In the case of the data from Jakarta, the intermittent qual-ity of the data required a diJerent type of analysis. Herethe hourly data were superposed over 1 month to form rep-resentative 24 h long data sets at each height of observa-tion, a so-called “superposed epoch” analysis. The zonal andmeridional winds were then harmonically analysed into aprevailing wind and 24 and 12 h tidal components.

The prevailing winds, and amplitudes and phases of the48- and 12 h waves over Collm were estimated by usinga regression analysis with linearly height-dependent coeL-cients applied to the half-hourly mean winds measured bythe LF D1 method. The 24 h tide cannot easily be investi-gated using this data set because the regular diurnal patternof data gaps would potentially lead to large errors. Jacobiet al. (1999) investigated this problem and concluded thatdisregarding the 24 h tide does not, however, lead to overlylarge errors in the calculation of 12 h tidal amplitudes andphases.

3. The global-scale wave model (GSWM)

The GSWM is a two-dimensional, linearised, steady-statenumerical tidal and planetary wave model which extendsfrom the ground to the thermosphere (Hagan, 1993; Haganet al., 1995, 1999, 2001; see also http://www.hao.ucar.edu/public/research/tiso/gswm/gswm.html). BrieOy, the GSWMtidal and planetary wave predictions are solutions to the lin-earised and extended Navier–Stokes equations for perturba-tion Aelds with characteristic zonal wavenumbers and peri-odicities that are assumed a priori along with a zonal meanbackground atmosphere. Zonal mean winds are included butthe meridional winds are neglected. The most recent versionof the model, hereafter GSWM-00, produces monthly mi-grating tidal climatologies and is a simple extension of theGSWM-98 of Hagan et al. (1999). The major diJerences be-tween the GSWM-98 and GSWM-00 versions is that in thelatter the seasonally variable GSWM-98 tropospheric heat-ing rates and eJective Rayleigh friction coeLcients (Hagan,1996; Hagan et al., 1999) were linearly interpolated for theGSWM-00 calculations. The remaining inputs and forcingsvary with month and remain consistent with those used in

GSWM-98. The suite of the GSWM-00 model inputs andparameterisations are described further below.

GSWM background temperature and density Aelds arespeciAed from the ground to the lower thermosphere bythe MSISE90 model (Hedin, 1991). At heights belowabout 20 km the background winds are taken from thesemiempirical model of Groves (1985, 1987), but thestratospheric=mesospheric jets and mesopause-region windsare based on the UARS high resolution doppler interferom-eter (HRDI) climatologies (Hagan et al., 1999). At heightsabove about 125 km, zonal mean zonal winds are takenfrom HWM93 model (Hedin et al., 1991, 1996).

The GSWM lower and middle atmospheric migratingtidal forcing is discussed in detail by Hagan (1996). Inessence, the GSWM employs Groves’ (1982) tropospherictidal heating formulae. These are based on 3-month aver-aged global models of speciAc humidity centred on January,April, July, and October. As mentioned above, these heat-ing rates were linearly interpolated in the GSWM-00 cal-culations. In the stratosphere, throughout the mesosphere,and into the lower thermosphere the GSWM tidal heat-ing is based on the parameterisation reported by Strobel(1978). This scheme accounts for ultraviolet absorption byozone in the Chappuis, Hartley, and Huggins bands and theHerzberg Continuum, as well as absorption by molecularoxygen in the Herzberg and Schumann-Runge Continuumand the Schumann-Runge bands. Hagan et al. (2001) usedthe CIRA international reference atmosphere ozone densi-ties (Keating et al., 1990) and MSISE90 molecular oxygendensities (Hedin, 1991) to calculate the GSWM-00 monthlytidal heating rates. Thermospheric heating at heights aboveabout 125 km is based on calculations of neutral gasheating from the National Centre for Atmospheric Re-search (NCAR) Thermosphere-ionosphere-electrodynamicsgeneral circulation model (TIE-GCM) (Hagan et al.,2001).

Tidal and planetary-wave dissipation occurs throughoutthe atmosphere and may be attributable to ion drag, molec-ular and eddy viscosity, conductivity, and radiative damp-ing. The treatment of molecular conductivity and viscosityas well as ion drag and Newtonian cooling parameterisa-tions of radiative damping in the GSWM have been dis-cussed by Hagan (1993). The GSWM employs a series ofeddy diJusion coeLcients and explicitly calculates the di-vergences of the associated heat and momentum Ouxes inthe model (cf. Forbes, 1982). The eddy diJusion coeL-cients account for the eJects of turbulence generated bygravity waves as they become unstable and Anally break inthe upper mesosphere and lower thermosphere (MLT). Theeddy diJusion coeLcients used are based on the results ofGarcia and Solomon (1985) as detailed by Hagan et al.(1995). The GSWM also includes an eJective Rayleigh fric-tion coeLcient (after Miyahara and Forbes, 1991) to accountfor the drag on the diurnal tide by gravity waves (Hagan etal., 1999). These seasonally variable coeLcients were lin-early interpolated for the GSWM-00 runs.

http://www.hao.ucar.edu/

mailto:public/research/tiso/gswm/gswm.html


4. Mean zonal wind

The mean wind through which the tides propagate is im-portant in determining their structure in the MLT region. Inthis part we report on comparisons between the model andradar zonal wind measurements to help assess the reliabilityof the background wind Aeld invoked for the GSWM-00 cal-culations. Fig. 2 shows a latitude cross-section of zonal meanwinds for the height range 90–95 km for each month of thecampaign. We follow the used in Fig. 1 symbols for pre-senting the diJerent ground-based observations. The solidand dashed lines represent the GSWM results for heights of88 and 96 km, respectively. The solid cross marks the zonalwind measured at Rothera in the same months, but in 1998rather than 1999. The prevailing zonal wind for those radarswith height resolution is presented in this Agure as an aver-age wind for the two height levels.

It is immediately clear from the Agure that there is a sub-stantial disagreement between the observed and model zonalwinds. In June, the model winter westerlies are up to 2–3times larger than the observations. The predicted summerwesterlies in the lower thermosphere of the middle latitudesare also larger than the measured winds. Generally, simi-lar overall latitudinal proAles however, are evident in com-paring the model and measurements during the campaignperiod. Only at high latitudes in the NH and during Julyin the SH do the zonal winds agree well with the model.The HRDI winds used in the GSWM feature a very strongsummer eastward jet above 90 km with a maximum at highlatitudes. The MWR measurements at Resolute Bay (Hock-ing, 2001) and ESRANGE also show evidence for such be-haviour, but the MFR measurements at Andenes shows arather weaker jet. Earlier measurements made near Kiruna,Sweden and reported by Glass et al. (1978) and Masse-beuf et al. (1979), also indicate a summer eastward jet (20–30 m=s) above 90 km, while measurements at Heiss Island(81◦N) (Portnyagin et al., 1993a) did not show evidence forsuch behaviour. This suggests that the strong eastward Oowextends at least as far as 75◦N in the MWR measurements,and that the weaker Oow observed by the Andennes MFRmay be due, in part, to instrumental diJerences in the windsmeasured by MFR and MWR techniques. This is consistentwith the comparisons of Manson et al. (1991) reported inSection 2: increases of the MFR winds by the suggested fac-tor of 1.55 for winds at 85–90 km brings the MWR=MFRin much better agreement, although the 95 km winds mayrequire an even greater ‘bias’ correction. It must also to benoted (Section 1) that total reOection of the MF radar-pulseoccurs near 90–95 km in summer months in hours near tolocal noon, and this will lead to errors of several kilometersin the assigned heights. Such errors will lead to underesti-mation of the winds, in the strong summer eastward jet. Wealso note that there is some similarity between the observedand model vertical gradients (not shown) in the zonal wind;it is mainly positive in the NH with a maximum around60◦N and negative for all sites in the SH.

-90 -75 -60 -45 -30 -15 0 15 30 45 60 75 90

LATITUDE (degree)

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88

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GSWM

-90 -75 -60 -45 -30 -15 0 15 30 45 60 75 90

LATITUDE (degree)

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Fig. 2. A latitude cross section of zonal mean winds at height range88–96 km for June, July and August 1999. Solid and dashed linesrepresent the GSWM-00 for heights 88 and 96 km, respectively.Solid dots represent MWR, solid diamonds—MFR, square—LFdrift measurements, triangles—IDI and crest presents the zonalwind at Rothera in 1998.

Fig. 2 clearly indicates some diJerence between the sum-mer mean zonal winds measured by MW and MF radars.On the average, the summer eastward winds measured bythe MWR are stronger than those measured by the MFR.This is well evident in August when the jet is very strong.


The comparison between the mean zonal wind measured bythe MWR and MFR during this 3-month PSMOS campaignsupports the result from the short-term (10 days) compari-son presented by Cervera and Reid (1995).

Several radars that participated in the PSMOS campaignare situated in the latitude range between 43 and 56◦N andcover longitudes from 107◦W to 142◦E. This arrangementallows some investigation of the longitudinal variability ofzonal winds and tides in the middle latitudes of the summerhemisphere. The longitudinal distribution of the zonal windis shown in Fig. 3, as all observations are shown by soliddots. The zonal wind at Juliusruh is marked by solid trianglesas its values are signiAcantly lower than all other measure-ments in this latitudinal belt. If this point is separated fromthe rest of the data, we can see that the zonal wind above theEastern part of Europe is stronger than above Canada and theUSA. This diJerence increases from June to August whenthe mean zonal wind above Canada is about 13 m=s, whilethat above Russia is about 20 m=s or more. This observationmay provide evidence for the existence of quasi-stationarynon-zonally structure in the prevailing zonal wind. A best-Atof these wind data to the sinusoidal pattern expected of astationary planetary wave of zonal wave number 1 is shownby the dashed lines in each panel of Fig. 3. The phase of thiswave is ∼ 80◦E and the amplitude increases from 2 m=s inJune to 5 m=s in August. Such longitudinal diJerences in thecirculation of the MLT region were considered by Lysenkoet al. (1994), where they were discussed in terms of the am-plitudes and phases of semiannual and annual oscillations.Another reason could be related to the asymmetries causedby longitudinal variations in the gravity wave drag. Holton(1984) noted that topographically forced waves will haveasymmetries in their forcing, which can lead, even in theabsence of stratospheric planetary waves, to planetary-scalezonal asymmetries in mesospheric momentum forcing whenthe waves dissipate. He showed that this could generateplanetary-scale disturbances in situ.

5. Semidiurnal tide

5.1. Latitudinal variability

Fig. 4 presents a latitudinal cross section of the 12 h tidalamplitude in the height range 90–95 km. The solid circlesrepresent the amplitude of the zonal component and the soliddiamonds the amplitude of the meridional component for allobservations. Similarly to the previous section, the semid-iurnal tidal amplitudes for those radars with height resolu-tion are presented in this Agure as an average amplitude forthe two height levels. Also, in the latitude range between 43and 55◦N there are several stations which have almost thesame latitude, but very diJerent longitudes (see Table 1). Inthis Agure we are interested in presenting only the latitudinaldistribution of the tidal amplitudes, so an average amplitudefrom these sites is used in the Agure (the sites are: Obninsk

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Mean Zonal Wind (Lat. 43N-56N)

LONGITUDE (degree)

Fig. 3. Longitudinal distribution of zonal mean wind observed in thelatitudinal range 43–56◦N. Zonal wind at Juliusruh is marked bysolid triangle. Dashed line represents the Atted stationary planetarywave with zonal wave number k = 1.

and Juliusruh; Saskatoon, Collm and Castle Eaton; LondonMFR, London MWR and Durham).

Comparisons between the GSWM-00 and the observa-tions of the tidal zonal components for each month of thecampaign are shown in the panels on the left of the Agures,


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June

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Amplitude of Semidiurnal Zonal Tide

ZONAL AMPLITUDE

GSWM 12-HOUR TIDE

MERIDIONAL AMPLITUDE

GSWM 12-HOUR TIDE

Amplitude of Semidiurnal Meridional Tide

Fig. 4. A latitude cross section of the semidiurnal tidal amplitudes at height range 90–95 km. Solid circles represent the zonal tidal amplitudesand solid diamonds—meridional amplitudes. Solid and dashed lines represent the GSWM-00 for heights 90.57 and 94.58, respectively. Theleft panels show the comparison for the zonal component and the right panels for the meridional component.


while those of the tidal meridional components are shownin the panels on the right. The discrepancy between the pre-dicted summer 12 h tidal amplitudes and the observationsis substantial (it is signiAcantly larger than the mean stan-dard deviations in the monthly-mean observations). The ob-served amplitudes are up to 2 times larger than the modelvalues. The winter 12 h tidal amplitudes are in reasonableagreement with the GSWM-00. However, the absence ofmeasurements around 50◦S where the predicted winter am-plitudes should be large makes this conclusion more tenta-tive.

In the summer hemisphere there is a slight tendency forthe meridional component to be stronger than the zonal com-ponent (particularly in June). In June, and partly in July, theamplitudes actually vary rather little with latitude. This factwas also noted by Vincent et al. (1989), who investigatedthe amplitudes and phases of the zonal component of the12 h tide observed over eight stations between about 65◦Nand about 65◦S at a height of 90 km during June solsticeconditions (see their Fig. 6).

The most remarkable feature observed in Fig. 4 is thestrong increase in the tidal amplitudes toward higher lati-tudes in the NH during August. The summer=early-autumnmaximum has been observed previously, mainly at high lat-itudes (Avery et al., 1989; Portnyagin et al., 1993b). How-ever, in these studies, the reported 12 h tidal amplitudesin the NH were about 15 m=s. Manson and Meek (1991),however, observed a similar ampliAcation of 12 h tidal am-plitudes over Saskatoon and TromsH with values rangingbetween 18 and 27 m=s. Here, in contrast, the 12 h tidalamplitudes observed over Andenes are about 18 m=s, whilethose over ESRANGE reach to about 25 m=s. The ESR mea-surements made in 1998 (shown in the Agure by a solidcross) reach even higher values, near 40 m=s, but this lastresult must be treated cautiously, because it is derived fromonly 9 days of observation, rather than an entire month asin the other data in the Agure. Also, we must remember theobserved diJerences between MFR and EISCAT measure-ments at 70◦N reported by Manson et al. (1992).

The GSWM-00 shows some increase in the 12 h tidal am-plitudes with latitude, to a maximum at ∼ 60◦N, but doesnot reproduce the increase of the tidal amplitudes beyondthese latitudes in August, apparent in the observations. Someexplanation of this feature may be found in the Forbes andVial (1989) model. In this model, the Labitzke et al. (1985)tabulations of the zonally averaged wind, temperature andpressure Aeld for each month of the year including hemi-spheric asymmetries were extended to 100 km by applyingthe geostrophic relationship to the mean zonal Aeld. Thesehemispheric asymmetries aJect the tidal propagation by dis-torting the tidal structures through the excitation of antisym-metric components. As a result of this the model indicateslarger tidal amplitudes in the NH with a maximum in am-plitude occurring above 85 km during August=September.

Fig. 5 presents comparisons between the model and theobserved vertical gradients in the 12 h tidal amplitude in the

altitude range 90–95 km for each month of the campaign(in this Agure only measurements from radars with heightresolution are included). The model predicts a general in-crease in the tidal amplitudes across this height interval andthis increase becomes substantial in the middle and high lat-itudes of the winter hemisphere. The observations in the SH,however, show a predominantly negative vertical gradient(i.e., tidal amplitudes that decrease with increasing height).As noted by Manson et al. (1999), this may in part be dueto a bias in MFR measurements above 90 km. In the win-ter of the NH, however, Manson et al. (1999) reported 12 htidal amplitudes generally increasing with height across theinterval 80–90 km. Nevertheless, we note that the modelamplitudes are generally a poor match to the observations,and so a comparison of the amplitude gradients may not besigniAcant.

Fig. 6 shows comparisons between the model and ob-served tidal phases. In general, the observed 12 h tidalphases are in agreement with the model prediction duringthe 3 months. Even the phases of the zonal tidal componentin August (when the amplitudes do not agree well) presentan excellent example of prediction. Some discrepancy is ob-served in the June solstice when the observed NH summerphases lead the model by ∼ 2 h. The observed tidal phasesshow that the 12 h tide is close to circular polarisation, witha 3 h time phase shift between the zonal and meridionalcomponents (i.e., in quadrature). In the NH (SH) the merid-ional component leads (lags) the zonal, hence the tidalcomponents rotate clockwise in the NH (counter clockwisein the SH), as expected. The equatorial data from Jakartashow some phase diJerences in the zonal component, withthe observations leading the model by ∼ 4 h in June and∼ 2 h in July. These diJerences are probably related tothe relative positions of the equatorial nodes for the modeland the planetary atmosphere (Manson et al., 1999). Thismeans that while the equatorial node for tidal modes willbe near to 0◦ in the model and in the planet’s atmosphere,asymmetries in the background atmosphere will diJer be-tween the two, meaning that the nodes will seen at diJerentlatitudes in model and real atmosphere, and that these willdiJer with season.

In Manson et al. (1999) the analysis of the verticaltidal wavelength was made using two diJerent approaches:(i) wind proAles between 65 and 100 km, and (ii) phasegradients calculated over 6 km centred near 87 km. Theresults clearly indicated that the phase gradients are in fairagreement with common wind proAle analysis. Followingthis approach Fig. 7 presents comparisons between modeland observed vertical gradients in tidal phase over theheight interval 90–95 km. The altitude range considered istoo small to reliably estimate the vertical wavelengths ofthe tide, but the data can still be used as crude indicatorsof the vertical wavelength. The observations show that the12 h tides in the winter SH are consistent with propagation.The near-zero gradients evident mostly in the NH summerobservations may indicate a superposition of modes rather


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LATITUDE (degree)

June

Semidiurnal Zonal Tide

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LATITUDE (degree)

June

Semidiurnal Meridional Tide

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LATITUDE (degree)

July

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Fig. 5. Same as Fig. 4, but for the vertical gradients of the semidiurnal amplitudes.

than no propagation. The Anite gradient in the summerGSWM-00 results poleward of 50◦N and above 80 km,indicating the wavelength of 30–40 km at high summerlatitudes is inconsistent with the observations.

According to the observed vertical phase gradients thewinter wavelengths are smaller than the summer ones.The NH vertical phase gradients gradually decrease fromJune to August, indicating some increase in the vertical


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Phase of Semidiurnal Zonal Tide

ZONAL PHASE

GSWM 12-HOUR TIDE

Phase of Semidiurnal Meridional Tide

MERIDIONAL PHASE

GSWM 12-HOUR TIDE

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Fig. 6. Same as Fig. 4, but for the phases of the semidiurnal tide.


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LATITUDE (degree)

July

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Semidiurnal Zonal Tide

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Semidiurnal Meridional Tide

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Fig. 7. Same as Fig. 4, but for the vertical gradients of the semidiurnal phases.

wavelength. In June and July the observed vertical gradi-ents of the meridional tidal component in the NH suggestsome modest decrease toward high latitudes, indicatingan increase in the tidal wavelength. Observations made at

Poker Flat (Avery et al., 1989) revealed that in summerwavelengths can be in excess of 150 km in summer, oreven evanescent. Very large vertical wavelengths duringNH summer have also been observed over Kiruna (Glass


et al., 1978) and by Manson et al. (1999) poleward of52◦N. In contrast to the observations, the GSWM-00 sug-gests rather too short wavelengths occur during summer atheights above 80 km and at latitudes poleward of 50◦N.

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Amplitude of Semidiurnal Zonal Tide (Lat. 43N-56N) Amplitude of Semidiurnal Meridional Tide (Lat. 43N-56N)

Fig. 8. Longitudinal distribution of the zonal (solid circles) and meridional (solid diamonds) semidiurnal amplitudes observed in thelatitudinal range 43–56◦N. Dashed line represents the Atted stationary planetary wave with zonal wave number k = 1.

5.2. Longitudinal variability

Fig. 8 shows the longitudinal distribution of the ob-served 12 h tidal amplitudes measured by those radars


situated in the latitude range 43–56◦N. The tidal amplitudesabove Eastern Europe are generally larger than those aboveCanada and the USA. This diJerence in tidal amplitudesincreases from June to August. This picture, analogous tothe diJerences in monthly-mean zonal wind, is evidence ofquasi-stationary, non-zonal, structure of the 12 h tidal am-plitude. Again, a monthly best-At to a stationary sinusoidalplanetary wave type pattern with zonal wave number 1 isshown by the dashed line. The phase is again ∼ 80◦E andfor the zonal component the amplitude changes from 4 m=sin June to 6 m=s in August and for the meridional compo-nent changes from 2 m=s in June to 5 m=s in August. Thebest-At procedure gives also the monthly-mean zonally aver-aged tidal amplitude for the studied latitudinal range. For thezonal component it changes from 9 m=s in June to 15 m=s inAugust, while for the meridional it changes from 10 m=s inJune to 15 m=s in August. The diJerence between the zon-ally averaged zonal and meridional tidal amplitudes showthat the mean meridional amplitudes are slightly larger thanthe zonal ones in June.

Fig. 9 shows the longitudinal distribution of the 12 h tidalphases. A similar best-At procedure indicates the amplitudeof the quasi-stationary structure of zonal wave number 1in June is small, about 0:5 h, while in July and Augustit is about 1 h. This means that the average phase diJer-ence between Saskatoon and Kazan, for example, is about1–2 h in July and August. Lysenko et al. (1994) noted thatdata from Kazan from June to October at practically all al-titudes demonstrate a systematic phase shift of 0.5–2 h to-wards later times for maxima in tidal amplitudes comparedto Saskatoon. The zonally averaged meridional phase lagsthe zonal one by exactly 3 h in July, by ∼ 3 h in Augustand by 2:5 h in June, indicating that the 12 h tide is close tocircular polarisation at mid-latitudes throughout the periodof the PSMOS campaign.

It was shown that in the summer 1999 the longitudinalvariations in the mean zonal wind and in the semidiurnal tideare very similar. In the frame of Holton (1984) idea the lon-gitudinal variations of the semidiurnal tide could be causedby the interaction between the tide and the zonally asym-metric gravity waves. Modelling studies (e.g. Miyahara andForbes, 1991; McLandress and Ward, 1994) suggest that theprimary mechanism for the tidal–gravity wave interactionis selective transmission and localised breaking due to thevariation in the speed and vertical shear of the winds. Thisacts as a damping of the tide and is similar to the planetarywave damping mechanism proposed by Miyahara (1985).

Jacobi et al. (1999) investigated the longitudinal varia-tion of the 12 h tide with data from six mid-latitude stationsin the narrow band between 52 and 56◦N. By consideringmonthly means of 12 h tidal amplitudes and phases fromthe period 1985–1995 it was shown that there is no obvi-ous longitudinally varying planetary-wave inOuence on thetidal structure in summer. One reason for this disagreementwith the results here is that we are considering data froma wider latitude range (some 12◦), and so some of the ap-

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Phase of Semidiurnal Tide (Lat. 43N-56N)

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Fig. 9. Same as Fig. 8, but for the phases of the semidiurnal tide.

parent longitudinal structure could in fact arise from lati-tudinal variations. In winter, however, Jacobi et al. (1999)found quasi-regular longitudinal variations of tidal ampli-tudes that correlated with the stratospheric stationary wavepattern. This suggests a coupling between the semidiurnaltide and the quasi- stationary waves in the stratosphere or


longitudinally varying ozone variability as a possible sourcefor longitudinal variations of the semidiurnal tide. The ac-tual processes that lead to the longitudinal variations of thesemidiurnal tide still remain unclear.

6. Diurnal tide

According to a classical (e.g. Kato, 1980) and sophisti-cated modern tidal theory and models (e.g. Hagan et al.,1995, 1999), the propagating diurnal, 24 h, tides reach largeamplitudes at low latitudes (30◦N–30◦S). Unfortunately,only a few radars were operating at these low latitudes dur-ing the summer 1999 PSMOS campaign.

6.1. Latitudinal variability

In our presentation of results for the 24 h tide, we fol-low the same presentations as for the 12 h tide above. Figs.10–13 show consecutively the latitudinal variability of theamplitudes, vertical gradients of amplitude, tidal phases andvertical gradients of phase. The observed tidal amplitudesand model predictions are in remarkably good agreement.Although there is a problem with the diurnal tide in that wehave no measurements at those latitudes where the ampli-tudes should be large.

The observed meridional 24 h tidal amplitudes in the NHsummer during June are slightly smaller than the model am-plitudes, but their latitudinal gradient strictly follows themodel predictions. At high latitudes the summer amplitudesare larger than the winter tidal amplitudes. In the NH duringAugust the meridional component is larger than the zonalcomponent. The comparison between the model and ob-served vertical gradients in amplitude for the SH (Fig. 11)are excellent for all stations except Adelaide; they simplycoincide with the predictions. For the NH the model showsnegative gradients between 40 and 60◦N and only some ofthe observations support this prediction.

The comparison between the model and observed phasesis satisfactory (Fig. 12). The observed summer zonal phases,as well as their latitude gradient, are in excellent agreementwith the model phases, although in the model the meridionalcomponent has a steeper latitudinal gradient than is seenin the observations. The observed phases generally lag themodel ones, and this time lag increases toward the lower lat-itudes. This result shows that the phase shifts between zonaland meridional components gradually decreases toward lowlatitudes. In July, for example, the meridional phase overResolute Bay leads the zonal phase by 6 h, while the merid-ional phase over Yamagawa leads the zonal phase only by2 h. Consequently, the 24 h tide is not in quadrature dur-ing summer in middle and lower latitudes. Manson et al.(1999) noticed that the relative phases between meridionaland zonal components are such as to favour quadrature be-low 85 km, and linear polarization above.

In contrast to the summer hemisphere, the phases in thewinter hemisphere are not in good agreement with the pre-dictions, particularly at high latitudes (the signiAcant diJer-ences between the model and the observed 24 h tidal phasesover Grahamstown will not be discussed here, because webelieve them to be connected with an equipment problem).The most probable reason for this discrepancy is that the24 h tidal amplitudes are small in winter at high latitudes andso the errors in determining the tidal phase increase signif-icantly. Manson (2000, private communication) has notedthat the NH winter phases for latitudes beyond 50◦N are inquite good agreement with the GSWM-00 and MFR obser-vations. The observations in the summer (NH) are mainlyvery close to zero phase gradients (Fig. 13), so long wave-lengths or evanescence is evident. The 24 h tide observedabove Jakarta appears to have an evanescent behaviour also.Both the model and observations do not indicate some sig-niAcant diJerence between the vertical phase gradient insummer and winter hemisphere in the studied altitude in-terval (model shows slightly higher phase gradient in sum-mer). However, both the model and the observations, indi-cate a decrease of the vertical phase gradients towards highlatitudes, probably because the wavelengths of the 24 h tidein the summer (NH) high latitudes are longer than those inlower latitudes. Long wavelengths in the summer high lat-itudes are reported by Avery et al. (1989). Manson et al.(1999) reported that in the winter of the NH the wavelengthsof the 24 h tide in the higher latitudes (beyond 50◦N) arealso longer than those in lower latitudes (the GSWM-95 wasused in this study).

6.2. Longitudinal variability

Fig. 14 shows the longitudinal distribution of the ob-served 24 h amplitudes measured by those radars situatedin the latitude range between 43 and 56◦N. In this case thelongitudinal variations are diJerent from those of the meanzonal wind and 12 h tides. In general, the tidal amplitudesabove Canada and USA are larger than the tidal amplitudesobserved above Eastern Europe. This is most clearly visi-ble in the zonal component. Again a best-At to the data of a“quasi-stationary planetary wave” of zonal wave number 1is shown by the dashed lines in the Agure. The phase of thiswave is ∼ 110◦W, or close to Saskatoon. In July, for exam-ple, the mean amplitude above Saskatoon is 16 m=s, whileabove Juliusruh or the UK it is 5–6 m=s. The At is better forthe zonal component where the amplitude of the stationarywave changes from 3 m=s for June to 4 m=s for July and2 m=s for August. The zonally averaged amplitudes for thezonal component increase from June to August from 8 to10 m=s.

The longitudinal variations of the tidal phases are pre-sented in Fig. 15. Except for the June data, which can be ap-proximated as a stationary wave number one with the samephase as for the amplitudes, the other data have more com-plicated behaviour. The phase shifts between the zonal and


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Amplitude of Diurnal Zonal Tide

ZONAL AMPLITUDE

GSWM 24-HOUR TIDE

Amplitude of Diurnal Meridional Tide

MERIDIONAL AMPLITUDE

GSWM 24-HOUR TIDE

Fig. 10. Same as Fig. 4, but for the amplitudes of the diurnal tide.

meridional components for the all seven stations in June is∼ 2 h and it is related to the linear polarization of the ob-served 24 h tide (Manson et al., 1999). Small phase diJer-ences are evident in some sites in July and August also.

It is well known from numerous measurements that the24 h tide at middle latitudes is much less stable than thesemidiurnal tide. Nevertheless, it appears that the longitu-dinal variability of the tidal amplitude can be approximated


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Fig. 11. Same as Fig. 5, but for the vertical gradients of the diurnal amplitudes.

as quasi-stationary planetary wave with zonal wave number1 during the summer. In the approximation of the longitu-dinal variability of tidal phases however we have to includestationary waves with higher zonal wave number.

7. Discussion and conclusions

Observations of mean winds and semidiurnal and diurnaltides in the MLT region were made during the PSMOS


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MERIDIONAL PHASE

GSWM 24-HOUR TIDE

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Phase of Diurnal Zonal Tide

Fig. 12. Same as Fig. 6, but for the phases of the diurnal tide.

Summer 1999 campaign of 3 months. Data from 22 ground-based radars (and from two other instruments withmeasurements for the same period but in 1998) allow usto investigate the ability of the GSWM-00 to simulate

the solar tides in the mesopause region (90–95 km). Herewe have found that the GSWM-00 provides a reasonableestimate of most of the tidal characteristics in the MLTregion. The 24 h tide modelling appears superior to that


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Fig. 13. Same as Fig. 7, but for the vertical gradients of the diurnal phases.

shown for the 12 h tide; but based upon these three sol-stice months, the model is becoming very realistic overmany height ranges and latitudes. Some discrepancies,however, still exist and they can be summarised as follows:

1. There is substantial disagreement between the observedzonal mean radar winds and the GSWM-00 backgroundzonal mean zonal winds in the height range 88–96 km.The model background winter westerlies are up to 2–3


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LONGITUDE (degree)LONGITUDE (degree)


Amplitude of Diurnal Zonal Tide (Lat. 43N-56N) Amplitude of Diurnal Meridionall Tide (Lat. 43N-56N)

Fig. 14. Same as Fig. 8, but for the amplitudes of the diurnal tide.

times larger than the observation, which are dominatedby MW and MF radars. We note the work of Portnyaginet al. (1999) which raises some concerns about the possi-bility of a bias in the satellite data. The GSWM includes

a very strong summer eastward jet above 90 km withmaximum at high latitudes; some measurements sup-port this jet, however the others do not show evidencefor such behaviour. The observations indicate some


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Fig. 15. Same as Fig. 9, but for the phases of the diurnal tide.

diJerence between the summer mean zonal winds mea-sured by MW and MF radars. On the average, thesummer eastward winds measured by the MWR arestronger than those measured by the MFR.

2. The discrepancy between the predicted summer semidi-urnal amplitudes and the observations is substantial; the

observed amplitudes are up to 2 times or more largerthan the predictions.

3. Some discrepancy is observed near the June solsticewhen the summer hemisphere phases of the 12 h tidelead the model by about ∼ 2 h.

4. The GSWM-00 predicts too large than observed phasegradients (too short wavelengths) of the 12 h tide duringsummer in the high latitudes.

5. An enormous increase of the 12 h tide toward high lati-tudes in August is evident in the NH; there is some sig-nature for amplifying the 12 h tide toward high latitudesin the model, but the observations are more than 2 timeslarger than the predictions.

6. The model has a steeper latitudinal phase gradient thando the observations in the meridional component of thediurnal tide; the observed phases generally lag the modelones, as this time lag increases toward the lower lat-itudes. The phase shift between zonal and meridionalphases gradually decreases with decreasing of the lati-tude, so it favours the linear polarization.

Some of the above-mentioned discrepancies are probablyconnected with the fact that the observations may includesignatures of non-migrating components that are not ac-counted for in this version of the GSWM. Non-migratingtides can be generated by a localised excitation source, suchas a longitudinal non-uniformity of water vapour contentand the cloud convective activity, and=or a land–sea contrastin the heat transfer processes within the planetary boundarylayers (Williams and Avery, 1996). A possible reason forthe observed enormous increase of the 12 h tide toward highlatitudes in August could be a result from the inOuence ofthe non-migrating semidiurnal tide with zonal wave numbers= 1, recently found by Portnyagin et al. (1998); Forbes etal. (1999) at the South Pole. It was shown also that this pre-dominantly summertime phenomenon has an eJect on theother Antarctic sites. These are the Arst reports that show thedominance of the polar non-migrating tide over the migrat-ing tide. They give rise to the question if this phenomenonis the basic feature of the Arctic MLT region also. TheGSWM-00 deAciencies may be related to an analogous fea-ture in the summer Arctic region. There is also the possibil-ity that the data contain unmodelled migrating componentsdue to tropospheric deep convective activity. Nevertheless,regardless of the discrepancies mentioned above, the com-parison between the GSWM-00 and the ground-based mea-surements of the tidal wind in the MLT region during thePSMOS Summer 1999 campaign is very encouraging and itmay be expected to improve the next version of the GSWM.

In addition to the above discussed comparisons an attemptwas made in this study to approximate the longitudinalvariability of the mean zonal wind and the tidal characteris-tics in the summer middle latitudes with a quasi-stationaryplanetary wave with zonal wave number 1. It was shownthat in the summer 1999 the longitudinal variations inthe mean zonal wind and in the semidiurnal tide are very


similar. This result, however, has to be accepted as verypreliminary. It would be better in future studies the longi-tudinal neutral wind and tidal variations to be investigatedby a two-dimensional frequency=wave number analysis toquantify non-migrating and migrating components. Suchanalysis, however, needs deAnitely more stations compara-tively uniformly distributed at least on the land in a narrowlatitudinal band.

An essential weak point of the PSMOS Summer 1999campaign was the lack of tropical stations. This is partic-ularly important for the diurnal tide where its amplitudeshould be large. The dynamics of the equatorial and tropicalregion is very important also for clarifying the phenomenain the summer MLT region having in mind the propagationof some disturbances from winter to summer hemisphere.So, it would be better for this fact to be kept in mind in thefuture campaigns.

Acknowledgements

Measurements over Collm, Obninsk, Kharkov and Kazanhas been supported by INTAS under grant No. 96-1669. TheNational Centre for Atmospheric Research (NCAR) is spon-sored by the National Science Foundation (NSF). The eJortsof M. E. Hagan are supported in part by the NSF CEDARprogram. The measurements at Durham were supported bythe University of New Hampshire and the National ScienceFoundation under grant ATM-9528224. The Rothera MFradar was jointly supported by the University of Coloradothrough NSF grant OPP-9319068 and by the UKNERC. TheUK MW radar data were kindly provided by H.G. Muller.The eJorts of D. Pancheva are supported by PPARC. Weare also grateful for suggested improvements, provided onthe original manuscript by Daniel Marsh. Suggestions fromanonymous reviewers are greatly acknowledged.

References

Avery, S.K., Vincent, R.A., Phillips, A., Manson, A.H., Fraser, G.J.,1989. High-latitude tidal behaviour in the mesosphere and lowerthermosphere. Journal of Atmospheric and Terrestrial Physics51, 595–608.

Berkey, F.T., Fish, C.S., Jones, G.O.L., 2001. Initial observationsof mesospheric winds using IDI radar measurements at the BearLake Observatory. Geophysical Research Letters 28, 135–138.

Burrage, M.D., Skinner, W.R., Marshall, A.R., Hays, P.B.,Lieberman, R.S., Franke, S.J., Gell, D.A., Ortland, D.A.,Morton, Y.T., Schmidlin, F.J., Vincent, R.A., Wu, D.L., 1993.Comparison of HRDI wind measurements with radar and rocketobservations. Geophysical Research Letters 20, 1259–1262.

Burrage, M.D., Skinner, W.R., Gell, D.A., Hays, P.B., Marshall,A.R., Ortland, D.A., Manson, A.H., Franke, S.J., Fritts, D.C.,HoJman, P., McLandress, C., Niciejewski, R., Schmidlin, F.J.,Shepherd, G.G., Singer, W., Tsuda, T., Vincent, R.A., 1996.Validation of mesosphere and lower thermosphere winds from

the high resolution Doppler imager on UARS. Journal ofGeophysical Research 101, 10,365–10,392.

Cervera, M.A., Reid, I.M., 1995. Comparison of simultaneous windmeasurements using colocated VHF meteor radar and MF spacedantenna radar systems. Radio Science 30, 1245–1261.

Charles, K., Jones, G.O.L., 1999. Mesospheric mean winds andtides observed by the Imaging Doppler Interferometer (IDI) atHalley, Antarctica. Journal of Atmospheric and Solar-TerrestrialPhysics 61, 351–362.

Deng, W., Salah, J.E., Clark, R.R., Franke, S.J., Fritts, D.C.,HoJmann, P., K7urschner, D., Manson, A.H., Meek, C.E.,Murphy, D., Nakamura, T., Palo, S.E., Riggin, D.M., Roble,R.G., Schminder, R., Singer, W., Tsuda, T., Vincent, R.A.,Zhou, Q., 1997. Coordinated global radar observations of tidaland planetary waves in the mesosphere and lower thermosphereduring January 20–30, 1993. Journal of Geophysical Research102, 7307–7318.

Djuth, F.T., Elder, J.H., 1993. The VHF meteor radar system usedduring the Arecibo Initiative in Dynamics of the Atmosphere(AIDA) campaign ’89. Journal of Atmospheric and TerrestrialPhysics 55, 229–239.

Forbes, J.M., 1982. Atmospheric tides, 1, Model description andresults for the solar diurnal component. Journal of GeophysicalResearch 87, 5222–5240.

Forbes, J.M., Vial, F., 1989. Monthly simulations of the solarsemidiurnal tide in the mesosphere and lower thermosphere.Journal of Atmospheric and Terrestrial Physics 51, 649–661.

Forbes, J.M., Salah, J.E., 1991. Mesosphere–thermosphere tidalcoupling during the September 21–25, 1987 LTCS-1 campaign.Journal of Geophysical Research 96, 1135–1145.

Forbes, J.M., Portnyagin, Yu., Makarov, N.A., Palo, S.E.,Merzlyakov, E.G., Zhang, X., 1999. Dynamics of the lowerthermosphere over South Pole from meteor radar windmeasurements. Earth, Planets and Space 51, 611–620.

Garcia, R.R., Solomon, S., 1985. The eJect of breaking gravitywaves on the dynamics and chemical composition of themesosphere and lower thermosphere. Journal of GeophysicalResearch 90, 3850–3868.

Glass, M., Bernard, R., Fellous, J.L., Massebeuf, M., 1978.The French meteor radar facility. Journal of Atmospheric andTerrestrial Physics 40, 923–931.

Groves, G.V., 1982. Hough components of water vapor heating.Journal of Atmospheric and Terrestrial Physics 44, 281–290.

Groves, G.V., 1985. A global reference atmosphere from 18 to80 km. AFGL report TR-85-0129.

Groves, G.V., 1987. Final scientiAc report. AFOSR Report84-0045.

Hagan, M.E., 1993. Quiet-time upper thermospheric winds overMillstone Hill between 1984 and 1990. Journal of GeophysicalResearch 98, 3731–3739.

Hagan, M.E., 1996. Comparative eJects of migrating solar sourceson tidal signatures in the middle and upper atmosphere. Journalof Geophysical Research 101, 21,213–21,222.

Hagan, M.E., Salah, J.E., 1995. Upper thermospheric variabilityover Millstone Hill during the LTCS-2 and LTCS-6 campaigns.Journal of Geophysical Research 100, 23,769–23,777.

Hagan, M.E., Forbes, J.M., Vial, F., 1995. On modeling migratingsolar tides. Geophysical Research Letters 22, 893–896.

Hagan, M.E., Burrage, M.D., Forbes, J.M., Hackney, J., Randel,W.J., Zhang, X., 1999. GSWM-98: results for migrating solartides. Journal of Geophysical Research 104, 6813–6828.


Hagan, M.E., Roble, R.G., Hackney, J., 2001. Modelingthermospheric tides. Journal of Geophysical Research 106,12,739–12,752.

Hedin, A.E., 1991. Extension of the MSIS thermosphere modelinto the middle and lower atmosphere. Journal of GeophysicalResearch 96, 1159–1172.

Hedin, A.E., et al., 1991. Revised global model of thermospherewinds using satellite and ground-based observations. Journal ofGeophysical Research 96, 7657–7688.

Hedin, A.E., et al., 1996. Empirical wind model for the upper,middle, and lower atmosphere. Journal of Atmospheric andTerrestrial Physics 58, 1421–1447.

Hines, C.O., Adams, G.W., Brosnahan, J.W., Djuth, F.T., Sulzer,M.P., Tepley, C.A., Van Baelen, J.S., 1993. Multi-instrumentobservations of mesospheric motions over Arecibo: comparisonsand interpretations. Journal of Atmospheric and TerrestrialPhysics 55, 241–287.

Hocking, W.K., 2001. Middle atmosphere dynamical studies atResolute Bay over a full year: mean winds, tides and specialoscillations. Radio Science 36, 1795–1822.

Hocking, W.K., Thayaparan, T., 1997. Simultaneous and colocatedobservation of winds and tides by MF and meteor radars overLondon, Canada (43◦N, 81◦W), during 1994–1996. RadioScience 32, 833–865.

Holton, J.R., 1984. The generation of mesospheric planetarywaves by zonally asymmetric gravity wave breaking. Journal ofAtmospheric Science 41, 3427–3430.

Jarvis, M.J., Jones, G.O.L., Jenkis, B., 1999. New initiativesin observing the Antarctic mesosphere. Advances and SpaceResearch 24 (5), 611–619.

Jacobi, Ch., Schminder, R., K7urschner, D., 1997. Measurements ofmesopause region winds over Central Europe from 1983 through1995 at Collm, Germany. Contribution to Atmospheric Physics70, 189–200.

Jacobi, Ch., Portnyagin, Yu.I., Solovjova, T.V., HoJmann, P.,Singer, W., Fahrutdinova, A.N., Ishmuratov, R.A., Beard, A.G.,Mitchell, N.G., Muller, H.G., Schminder, R., K7urschner, D.,Manson, A.H., Meek, C.E., 1999. Climatology of the semidiurnaltide at 52–56◦N from ground-based radar wind measurements1985–1995. Journal of Atmospheric and Solar-TerrestrialPhysics 61, 975–991.

Jacobi, Ch., Lange, M., K7urschner, D., Manson, A.H., Meek, C.E.,2000. A long-term comparison of Sakatoon MF radar and CollmLF D1 mesosphere-lower thermosphere wind measurements.Physics and Chemistry of Earth (Part C), 26, 419–424.

Jones, G.O.L., Charles, K., Jarvis, M.J., 1997. First mesosphericobservations using an imaging Doppler interferometer adaptationof the dynasonde at Halley, Antarctica. Radio Science 32, 2109–2122.

Kato, S., 1980. Dynamics of the Upper Atmosphere. D. Reidel,Norwell, MA, 233pp.

Keating, G.M., Pitts, M.C., Chen, C., 1990. Improved referencemodels for middle atmosphere ozone. Advances and SpaceResearch 10, (6)37–(6)49.

Khattatov, B.V., Geller, M.A., Yudin, V.A., Hays, P.B., Skinner,W.R., Burrage, M.B., Franke, S.J., Fritts, D.C., Isler, J.R.,Manson, A.H., Meek, C.E., McMurray, R., Singer, W., HoJman,P., Vincent, R.A., 1996. Dynamics of the mesosphere andthermosphere as seen by MF radars and by the High-ResolutionDoppler Imager=UARS. Journal of Geophysical Research 10,1,10,393–10,404.

Kingsley, S.P., Muller, H.G., Nelson, L., ScholeAeld, A., 1978.Meteor winds over SheLeld. Journal of Atmospheric andTerrestrial Physics 40, 917–922.

K7urschner, D., Schminder, R., 1986. High-atmosphere wind proAlesfor altitudes between 90 and 110 km obtained from D1 LFwind measurements over Central Europe in 1983=84. Journal ofAtmospheric and Terrestrial Physics 48, 447–453.

Labitzke, K., Barnett, J.J., Edwards, B. (Eds.), 1985. ReferenceMiddle Atmosphere, Handbook for MAP. 16, 311–318, ICSU(SCOSTEP), Urbana, Illinois.

Lieberman, R.S., Robinson, W.A., Franke, S.J., Vincent, R.A.,Isler, J.R., Fritts, D.C., Manson, A.H., Meek, C.E., Fraser, G.J.,Fahrutdinova, A., Hocking, W., Thayaparan, T., Igarashi, K.,Nakamura, T., Tsuda, T., 1998. HRDI observations of meanmeridional winds at solstice. Journal of Atmospheric Science55, 1887–1896.

Lloyd, N., Manson, A.H., McEwen, D.J., Meek, C.E., 1990.A comparison of middle atmospheric dynamics at Saskatoon(52◦N, 107◦W) as measured by a medium-frequency radar anda Fabry–Perot interferometer. Journal of Geophysical Research95, 7653–7660.

Lysenko, I.A., Portnyagin, Yu.I., Fahrutdinova, A.N., Ishmuratov,R.A., Manson, A.H., Meek, C.E., 1994. Wind regime at80-11-km at mid-latitude of the northern hemisphere. Journal ofAtmospheric and Terrestrial Physics 56, 31–42.

Manson, A.H., Meek, C.E., 1986. The dynamics of the mesosphereand lower thermosphere at Saskatoon (52◦N). Journal ofAtmospheric Science 43, 276–284.

Manson, A.H., Meek, C.E., Schminder, R., K7urschner, D., Clark,R.R., M7uller, H.G., Vincent, R.A., Phillips, A., Fraser, G.J.,Singer, W., Kazimirovsky, E.S., 1990. Tidal winds from theMLT global radar network during the Arst LTCS campaignSeptember 1987. Journal of Atmospheric and Terrestrial Physics52, 175–183.

Manson, A.H., Meek, C.E., Avery, S.K., Fraser, G.J., Vincent,R.A., Phillips, A., Clark, R.R., Schminder, R., Kurschner, D.,Kazimirovsky, E.S., 1991. Tidal winds from the mesosphere,lower thermosphere global radar network during the secondLTCS campaign: December 1988. Journal of GeophysicalResearch 96, 1117–1127.

Manson, A.H., Meek, C.E., 1991. Climatologies of mean winds andtides observed by medium frequency radars at TromsH (70◦N)and Saskatoon (52◦N) during 1987–1989. Canadian Journal ofPhysics 69, 966–975.

Manson, A.H., Meek, C.E., Brekke, A., Moen, J., 1992. Mesosphereand lower thermosphere (80–120 km) winds and tides fromnear TromsH (70◦N, 19◦E) comparisons between radars (MF,EISCAT, VHF) and rockets. Journal of Atmospheric andTerrestrial Physics 54, 927–950.

Manson, A., Fan Yi, Hall, G., Meek, C., 1996. Comparison betweeninstantaneous wind measurements made at Saskatoon (52◦N,107◦W) using the colocated medium frequency radars andFabry–Perot interferometer instruments: climatologies (1988–1992) and case studies. Journal of Geophysical Research 101,29,553–29,563.

Manson, A.H., Meek, C.E., Hagan, M., Hall, C., Hocking, W.,MacDougall, J., Franke, S., Riggin, D., Fritts, D., Vincent,R., Burrage, M., 1999. Seasonal variations of the semi-diurnaltides in the MLT: multi-year MF radar observations from 2 to70◦N, and the GSWM tidal model. Journal of Atmospheric andSolar-Terrestrial Physics 61, 809–828.


Massebeuf, M., Bernard, R., Fellous, J.L., Glass, M., 1979. Themean zonal circulation in the meteor zone above Garchy(France) and Kiruna (Sweden). Journal of Atmospheric andTerrestrial Physics 41, 647–655.

McLandress, C., Ward, W.E., 1994. Tidal=gravity wave interactionsand their inOuence on the large-scale dynamics of the middleatmosphere: model results. Journal of Geophysical Research 99,8139–8155.

Meek, C.E., Manson, A.H., Burrage, M.D., Garbe, G., Cogger,L.L., 1997. Comparisons between Canadian prairies MF radars,FBI (green and OH lines) and UARS HRDI systems. AnnalesGeophysicae 15, 1099–1110.

Miyahara, S., 1985. Suppression of stationary planetary wavesby internal gravity waves in the mesosphere. Journal ofAtmospheric Science 42, 100–107.

Miyahara, S., Forbes, J.M., 1991. Interaction between gravitywaves and the diurnal tide in the mesosphere and lowerthermosphere. Journal of Meteorological Society of Japan 69,523–531.

Namboothiri, S.P., Manson, A.H., Meek, C.E., 1993. E region realheights and their implications for MF radar-derived wind andtidal climatologies. Radio Science 28, 187–202.

Palo, S.E., Hagan, M.E., Meek, C.E., Vincent, R.A., Burrage,M.D., McLandress, C., Franke, S.J., Ward, W.E., Clark, R.R.,HoJmann, P., Johnson, R., K7urschner, D., Manson, A.H.,Murphy, D., Nakamura, T., Portnyagin, Yu., Salah, J.E.,Schminder, R., Singer, W., Tsuda, T., Vitdi, T.S., Zhou, Q.,1997. An intercomparison between the GSWM, UARS, andground based radar observations: a case-study in January 1993.Annales Geophysicae 15, 1123–1141.

Phillips, A., Manson, A.H., Meek, C.E., Llewellyn, E.J., 1994. Along-term comparison of middle atmosphere winds measuredat Saskatoon by a medium-frequency radar and Fabry–Perotinterferometer. Journal of Geophysical Research 99, 12,923–12,935.

Portnyagin, Yu.I., Forbes, J.M., Fraser, G.J., Vincent, R.A., Avery,S.K., Lysenko, I.A., Makarov, N.A., 1993a. Dynamics ofthe Antarctic and Arctic mesosphere and lower thermosphereregions-I. The prevailing wind. Journal of Atmospheric andTerrestrial Physics 55, 827–841.

Portnyagin, Yu.I., Forbes, J.M., Fraser, G.J., Vincent, R.A., Avery,S.K., Lysenko, I.A., Makarov, N.A., 1993b. Dynamics ofthe Antarctic and Arctic mesosphere and lower thermosphereregions-II. The semidiurnal tide. Journal of Atmospheric andTerrestrial Physics 55, 843–855.

Portnyagin, Yu., Makarov, N.A., Chebotarev, R.P., Nikonov,A.M., Kazimirovsky, E.S., Kokourov, V.D., Sidorov, V.V.,Fahrutdinova, A.N., Cevolani, G., Clark, R.R., K7urschner,D., Schminder, R., Manson, A.H., Meek, C.E., Muller, H.G.,Stoddard, J.C., Singer, W., HoJmann, P., 1994. The wind regime

of the mesosphere and lower thermosphere during the DYANAcampaign—II. Semi-diurnal tide. Journal of Atmospheric andTerrestrial Physics 56, 1731–1752.

Portnyagin, Yu., Forbes, J.M., Makarov, N.A., Merzlyakov, E.G.,Palo, S., 1998. The summertime 12 h wind oscillation with zonalwavenumber s = 1 in the lower thermosphere over the SouthPole. Annales Geophysicae 16, 828–837.

Portnyagin, Yu.I., Solovjova, T.V., Wang, D.Y., 1999. Some resultsof comparison between the lower thermosphere zonal winds asseen by the ground-based radars and WINDII on UARS. Earth,Planets and Space 51, 701–709.

Roper, R.G., 1984. MWR-meteor wind radars. Middle AtmosphereProgram Handbook. 13, 124-134, ICSU (SCOSTEP), Urbana,Illinois.

Salah, J.E., Clark, R.R., Forbes, J.M., Manson, A.H., Avery,S.K., Schminder, R., 1994. Radar observations of thesemidiurnal tide in the mesosphere and lower thermosphere atmidlatitudes. Journal of Atmospheric and Terrestrial Physics 56,1251–1261.

Singer, W., HoJmann, P., Manson, A.H., Meek, C.E., Schminder,R., K7urschner, D., Kokin, G.A., Knyazev, A.K., Portnyagin, Yu.,Makarov, N.A., Fahrutdinova, A.N., Sidorov, V.V., Cevolani,G., Muller, H.G., Kazimirovsky, E.S., Gaidukov, V.A., Clark,R.R., Chebotarev, R.P., Karadjaev, Y., 1994. The wind regimeof the mesosphere and lower thermosphere during the DYANAcampaign—I. Prevailing wind. Journal of Atmospheric andTerrestrial Physics 56, 1717–1729.

Strobel, D.F., 1978. Parametrization of the atmospheric heatingrate from 15 to 120 km due to O2 and O3 absorption of solarradiation. Journal of Geophysical Research 83, 6225–6230.

Tsuda, T., Nakamura, T., Kato, S., 1987. Mean winds observed bythe Kyoto meteor radar in 1983–1985. Journal of Atmosphericand Terrestrial Physics 49, 461.

Turck, R.S., Miller, K.L., Roper, R.G., Brosnahan, J.W., 1995.Mesospheric wind studies during AIDA Act ’89: morphologyand comparison of various techniques. Journal of Atmosphericand Terrestrial Physics 57, 1321–1343.

Van Eyken, A.P., Williams, P.J.S., Buchert, S.C., Kunitake,M., 2000. First measurements of tidal modes in the lowerthermosphere by the EISCAT Svalbard Radar. GeophysicalResearch Letters 27, 931–934.

Vincent, R.A., Tsuda, T., Kato, S., 1989. Asymmetries inthe mesospheric tidal structure. Journal of Atmospheric andTerrestrial Physics 51, 609–616.

Vincent, R.A., Lesicar, D., 1991. Dynamics of the equatorialmesosphere: Arst results with a new generation partial reOectionradar. Geophysical Research Letters 18, 825.

Williams, C.R., Avery, S.K., 1996. Non-migrating diurnal tidesforced by deep convective clouds. Journal of GeophysicalResearch 101, 4079–4091.

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