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Wind observations in the MLT region over Southern Japan, by using foil chaff technique, Yamagawa MF radar and the NW radar
Pergamon www.elsevier.nl/locate/asr
0 1999 COSPAR.
Adv. Space Res. Vol. 24, No. 5, pp. 575-578. 1999 Published by Elsevier Science Ltd. All rights reserved Printed in Great Britain 0273- 1177/99 $20.00 + 0.00
PII: SO273-1177(99)00203-3
Wind Observations in the MLT Region over Southern Japan, by Using Foil Chaff Technique, Yamagawa MF Radar and the MU Radar Y. Murayama’ , K. Igarashi’, I. Nishimuta’, R. Yamazaki’, K.-I. Oyama’,, T. 13uda3, T. Nakamura3, S. Fukao3, H.-U. Widdel’, and K. Schlege14 I. Communications Research Laboratory, Koganei, Tokyo 184-8795, JAPAN. 2. Institute of Space and Astronautical Science, Sagamihara, Kanagawa 229-8510, JAPAN. 3. Radio Atmospheric Science Center; Kyoto University, Uji, Kyoto 611-0011, JAPAN. 4. Max-Planck-Institut fr Aeronomie, Katlenburg-Landau, GERMANE
ABSTRACT Wind fields observed with foil chaff technique in the mesosphere and lower thermosphere (80-98 km in altitude) by means of two micro-rockets at 1200 and 1315 UT on 14 January 1997 from Uchinoura, Japan (31N, 131E) are compared with the winds simultaneously observed with the MU radar (MUR; 35N, 136E) and the Yamagawa MF radar (MFR; 31N, 131E). The chaff and MFR results showed good agreement at 80-88 km, and MFR data were missing at higher altitudes. A coherent structure was commonly detected in the chaff, MFR, and the MUR winds, 0 1999 COSPAR. Published by Elsevier Science Ltd. likely caused by a large scale gravity wave. INTRODUCTION The foil chaff is one of several in-situ techniques to directly measure MLT (mesosphere and lower thermosphere) wind velocity. Motions of a cloud of many metalized plastic film pieces, descending very slowly (c 100 m/s) at MLT heights, are used to determine wind velocity as well as fine structures of the wind fields which radar or other techniques may be difficult to achieve [e.g., Wu and Widdel, 19921. On the other hand, the MF radar can observe MLT winds on a temporally continuous basis, which usually employs spaced antennas (SA method). More than twenty MF radars now operate at various sites at low, mid and high latitudes, contributing to studies of planetary, tidal, and gravity waves and mean winds in the MLT region by a number of researchers [e.g., Vincent and Lesicar, 1991; Brown, 1992; Manson and Meek, 1993; Igarashi et al., 19961. Hines et al. [1993] reported a variable agreement between wind velocities observed with the Are&o IS radar and the I-IF radar with the SA technique at altitudes higher than 8.5-90 km, leading to the controversy on the MF/HF radar SA wind measurement. SA wind measurements with the MF radar have been compared with other techniques such as meteor radar [Stubbs, 1973; Cervena and Reid, 19951 and the UARS satellite [Burrage et al., 19961, where good agreements were found by Stubbs but the others tended to show somewhat smaller wind amplitude values of MF radar than the other techniques. Reid [1996] suggested that the argument by Hines et al. might not necessarily be valid Recent studies report wind estimation improvement by modifying the system setup [Holdsworth, 1995; Reid, 1996; Vincent et al., 1994; Igarashi, private communication,l996]. In this paper, results of the chaff (foil chaff) experiments- at 1200 and 1315 UT on 14 January 1996 at the Kagoshima Space Center (KSC), Uchinoura (31N, 131E), Japan, are compared with simultaneous ground-based observations with the CRL Yamagawa MF radar (31N, 131E) about 50 km west of KSC, and the MU radar (35N, 136E) about 600 km north-east of KSC using a meteor wind measurement mode (MU/meteor experiment). These foil chaff experiments are the first ones which were conducted successfully outside the European region. Murayama et al. [1998] also gives more results and discussions for the same observations. 575
576
Y. Murayama
et al.
EXPERIMENTS AND DATA PROCESSING For this study, we conducted two foil chaff experiments at 1200 and 1315 UT on 14 January 1997, by using two Viper III-A micro-meteorological rockets launched from KSC, Uchinoura (31N, 131E). The MU radar (35N, 136E; 600 km east of the chaff release location), and the Yamagawa MF radar (31N, 131E; 100 km west) simultaneously observed MLT wind fields. The MU radar observed meteor winds at an altitude range of 75-100 km, with time and vertical resolution of 30 min and 1 km, respectively [for the technique and details, see, e.g., Nakamura et al., 19911. The Yamagawa MF radar, operating at 1.995MHz continuously since August 1994, was observing horizontal wind velocity at the 80--100 km altitudes (night time condition) with time and vertical resolution of 2 min and 7 km, respectively [Igarashi et al., 19961. Although MF radars often operate with the vertical resolution of 3-4 km, the bandwidth and vertical resolution of our system have been limited since September 1996 to avoid interference with other communications. The foil chaff technique was developed by H.-U. Widdel of Max-Planck Institut fiir Aeronomie [e.g., Widdel, 19871 for observing wind velocity profiles at the MLT heights by employing a number of small strips of thin metalized plastic film [e.g., Widdel, 1990; von Zahn, 1987; Thrane, 19881. For our experiments foil with the 1 micrometer thickness (mass-to-area ratio =1.7 g/m*) were used for the altitude range of 80- 100 km. Each chaff strip was 25 mm long and 5 mm wide. The length is determined to be approximately half-wavelength long of the radio wave of the C-band tracking radar. 6000 strips were mounted on a rocket payload The foil strips mounted on the rocket were ejected at the altitude of about 110 km to form a chaff “cloud”, then they advected with the ambient wind motions during their descent. The location such as range, and azimuthal and elevation angles, of this chaff cloud is determined by the tracking radar. After conversion to the Cartesian coordinate system and averaging over each 300 m interval, descending speed and horizontal velocities were obtained by temporal differentiation. OBSERVED RESULTS Figure 1 shows observed wind velocities by the two chaff experiments at 1200 and 1315 UT on 14 January 1997, and hourly horizontal winds by the Yamagawa MF radar (hereafter MFR) and the MU radar (MUR), all being after the 7-km smoothing. MFR data at altitudes >86 and >88 km were missing around the two rocket experiment periods at 1200 and 1315 UT, respectively. MUR meteor observation covered the height range wider than that of the chaff experiments.
ZONAZ. 1200
COMPONENT UP
970114
MERJDIONAL 1200
COMPONENT UT 970114
ZOITAL 1315
COMPONENT UT 970114
MERIDIONAL
l.?ls
COMPONENT
UT 970114
100
100
95
-20 0 20 40 WlNIl VEXOUTY
81) 80 (m/a)
-20 0 LO 4a WIND VEu)ClTY
8Q a0 (m/s)
-20 0 20 40 WIND VEMClTY
80 80 (m/s)
-20 0 20 44 WND VELAXlTY
60 80 (m/s)
Fig. 1. Wind velocities observed by the two chaff experiments (solid) at 1200 (left two panels) and 1315 UT (right two panels ) on 14 January 1997, and hourly horizontal winds by the Yamagawa MF radar (asterisk and solid line) and the MU radar (dashed), all being after the 7-km smoothing.
MLT
Winds
by Chaff
MU-MWR / KSC CHAFF EASTWARD WIND 970114
and Radar
over Southern
Japan
MU-MIVR
NORTHWA d
KSC CHAFF WIND 970114
100 '"I"'I"'I'"k" -______.__._.._ ~.=.~.-~--=~...;._,.^.T.rr,_ -=-......--_ /q--,1 -..~.;;.,.,,-,.,,, ....----...........................~-~.~ _......‘..._..._....______ --...-- _-.-.-__---___ ._..___.........__...~....~.......----..
100
95 -2 s
*----._ cc--_-_____. ._...._.......___ -..
90
------L-"'
is E 2 85
a
10
12 14 16 8 10 14 16 U?(HR) LJT (HR) Fig. 2. Time series of the chaff (filled dot), MFR (solid line), and MUR (dashed line) wind velocity with 7-km smoothing. For vertical scale, the l-km interval corresponds to 50 m/s. The zonal component at 1200 UT at altitudes of 82-86 km shows weak eastward winds of 5-6 m/s and l-5 m/s for chaff and MFR data, respectively, while the zonal winds at 13 15 UT show velocities of O-20 m/s and l-5 m/s for chaff and MFR, respectively, at 80-86 km, For the meridional component at 1200 UT, the chaff and MFR winds at 82-86 km were northward with amplitudes of 5-25 m/s and 15-20 m/s, respectively, and at 1315 UT they were 1322 and 30-40 m/s, respectively, at SO-86 km. These results suggest that, between the chaff and MFR data, the zonal component agree well, at least in the observed height range, and the meridional component at 1200UT also agrees reasonably. However, the meridional component at 13 15 UT showed variable agreement, with difference increasing up to 50 m/s with altitude decreasing from 86 to 80 km. The MUR wind profiles showed large vertical-scale structure, and their possible temporal evolution from 1200 to 1315 UT. Time series of vertical profiles (not shown here) suggest a wave structure with the vertical scale of -20 km and the wave period of 11-14 hr, which may be a large scale gravity wave. This wave structure also can be seen in chaff profile with vertical phase shift of -5 km, implying that the same gravity wave might be detected at the two sites with a distance of 600 km. Time series of the chaff, MFR, and MUR wind velocity with 7-km smoothing are shown in Figure 2. The zonal component show very good agreement between chaff and MFR winds, with the similar values and temporal trends. The chaff meridional winds at 1200UT agreed well with MFR, but the difference of chaff-MFR values at 1315UT is again evident. SUMMARY The experimental results of the two foil chaff experiments were shown, at the Kagoshima Space Center (KSC), Uchinoura (31N, 131E), Japan. at 1200 and 1315 UT on 14 January 1996, being the first outside the European region. Observed wind velocity profiles were compared with the MU radar meteor wind (35N, 136E) and the CRL
578
Y. Murayama
et al.
Yamagawa MF radar SA winds (31N, 131E) 50 km west of KSC. The zonal component of the chaff winds generally agreed well with that of MFR winds, at the altitudes of 80-88 km, regarding height structure and temporal trends. The chaff meridional winds at 1200 UT agreed reasonably with MFR winds, while the largest difference found was 50 m/s at 80-84 km at 1315 UT. The wind fields at the two sites with the 600 km distance tended to show a coherent structure of a large scale gravity wave. ACKNOWLEDGEMENTS The Yamagawa MF radar of the CRL Yamagawa Radio Observatory was constructed with help of Drs. R. A. Vincent and I. Reid, University of Adelaide, Australia. The MU radar belongs to, and is operated by the Radio Atmospheric Science Center, Kyoto University. REFERENCES Brown, W. 0. J., MF radar interferometry, Ph.D. thesis, University of Canterbury, NZ, pp.303, 1992. Burrage, M. D., W. R. Skinner, D. A. Gell, P. B. Hays, A. R. Marshall, D. A. Chtland,A. H. Manson, S. J. Franke, D. C. Fritts, P Hoffman, C. McLandress, R. Niciejewski, F. J. Schmidlin, Ci Ci Shepherd, W. Singer, T. Tsuda, and R. A. Vincent, Validation of mesosphere and lower thermosphere winds from the high resolution Doppler imager on UARS, J. Geophys. Res., 101,10365-10392, 1996. Cervena, M. A., and I. M. Reid, Comparison of simultaneous wind measurements using colocated VHF meteor radar and MF spaced antenna radar systems, Radio Sci., 30, 1245- 126 1, 1995. Holdsworth, D. A., On the analysis of spaced sensor data, Ph.D. Thesis, University of Adelaide, Australia, 1995. Hines, C. O., Ci W. Adams, J. W. Brosnahan, F. T. Djuth, M. P. Sulzer, C. A. Tepley, and J. S. Van Baelen, Multiinstrument observations of mesospheric motions over Arecibo: comparisons and interpretations, J. Atmos. Terr. Phys., 55,241-287, 1993. Igarashi, K., I. Nishlmuta, Y. Murayama, T. Tsuda, T. Nakamura, and M. Tsutsumi, Comparison of wind measurements between Yamagawa MF radar and the MU radar, Geophys. Res. Lett., 23,3341, 1996. Manson, A. H. and C. E. Meek, Characteristics of gravity waves (10 mm-6 hours) at Saskatoon (52’N, 107’W): Observations by the phase coherent medium frequency radar, J. Geophys. Res., 98,20357-20367,1993. Murayama, Y., K. Igarashi, I. Nishimuta, R. Yamazaki, K.-I. Oyama, T. Tsuda, T. Nakamura, S. Fukao, H.-U. Wlddel, and K. Schlegel, Cooperative wind observation in the upper mesosphere and lower thermosphere with foil chaff technique, the MU radar, and Yamagawa MF radar, submitted to Earth, Planets and Space, 1998. Nakamura, T., T. Tsuda, M. Tsutsumi, K. Klta, T. Uehara, S. Kato, and S. Fukao, Meteor wind observations with the MU radar, Radio Sci., 26,857-869, 1991. Stubbs, T. J., The measurement of winds in the D-region of the ionosphere by the use of partially reflected radio waves, J. Atmos. Terr. Phys., 35,909-919, 1973. Reid, I. M., On the measurement of gravity waves, tides and mean winds in the low and middle latitude mesosphere and thermosphere with MF radar, Adv. Space Res., 18, (3)131-(3)140, 1996. Thrane, E. V., The MAC/SINE and MAC/EPSILON Campaigns, Paper presented at COSPER meeting in Espoo, Finland, to be published in Adv. Space Res., 1988. Vincent, R. A., and D. Lesicar, Dynamics of the equatorial mesosphere: First results with a new generation partial reflection radar, Geophys. Res. Lett., 18, 825-828, 1991. Vincent, R. A., D. A. Holdsworth, I. M. Reid and M. A. Cervena, Spaced antenna wind measurements: The effects of signal saturation, Proceedings of the workshop on Wind Observations in the Middle Atmosphere, Paris, 15- 18 November, 1994. Von Zahn U., J. Atmos. Terr. Phys., 49, 723-741, 1987. Widdel, H.-U., Vertical movements in the middle atmosphere derived from foil cloud experiments, J. Atmos. Terr. Phys., 49, 607, 1987. Widdel, H.-U., Foil chaff cloud as a tool for in-situ measurements of atmospheric motions in the middle atmosphere: their flight behavior and implications for radar tracking, it J. Atmos. Terr. Phys., 52, 89-101, 1990. Wu, Y.-H. and H.-U. Widdel, Saturated gravity wave spectrum in the polar summer lower thermosphere observed by foil chaff during campaign “Sodium 88”, J. Atmos. Sci., 49, 1781-1789, 1992.
0 1999 COSPAR.
Adv. Space Res. Vol. 24, No. 5, pp. 575-578. 1999 Published by Elsevier Science Ltd. All rights reserved Printed in Great Britain 0273- 1177/99 $20.00 + 0.00
PII: SO273-1177(99)00203-3
Wind Observations in the MLT Region over Southern Japan, by Using Foil Chaff Technique, Yamagawa MF Radar and the MU Radar Y. Murayama’ , K. Igarashi’, I. Nishimuta’, R. Yamazaki’, K.-I. Oyama’,, T. 13uda3, T. Nakamura3, S. Fukao3, H.-U. Widdel’, and K. Schlege14 I. Communications Research Laboratory, Koganei, Tokyo 184-8795, JAPAN. 2. Institute of Space and Astronautical Science, Sagamihara, Kanagawa 229-8510, JAPAN. 3. Radio Atmospheric Science Center; Kyoto University, Uji, Kyoto 611-0011, JAPAN. 4. Max-Planck-Institut fr Aeronomie, Katlenburg-Landau, GERMANE
ABSTRACT Wind fields observed with foil chaff technique in the mesosphere and lower thermosphere (80-98 km in altitude) by means of two micro-rockets at 1200 and 1315 UT on 14 January 1997 from Uchinoura, Japan (31N, 131E) are compared with the winds simultaneously observed with the MU radar (MUR; 35N, 136E) and the Yamagawa MF radar (MFR; 31N, 131E). The chaff and MFR results showed good agreement at 80-88 km, and MFR data were missing at higher altitudes. A coherent structure was commonly detected in the chaff, MFR, and the MUR winds, 0 1999 COSPAR. Published by Elsevier Science Ltd. likely caused by a large scale gravity wave. INTRODUCTION The foil chaff is one of several in-situ techniques to directly measure MLT (mesosphere and lower thermosphere) wind velocity. Motions of a cloud of many metalized plastic film pieces, descending very slowly (c 100 m/s) at MLT heights, are used to determine wind velocity as well as fine structures of the wind fields which radar or other techniques may be difficult to achieve [e.g., Wu and Widdel, 19921. On the other hand, the MF radar can observe MLT winds on a temporally continuous basis, which usually employs spaced antennas (SA method). More than twenty MF radars now operate at various sites at low, mid and high latitudes, contributing to studies of planetary, tidal, and gravity waves and mean winds in the MLT region by a number of researchers [e.g., Vincent and Lesicar, 1991; Brown, 1992; Manson and Meek, 1993; Igarashi et al., 19961. Hines et al. [1993] reported a variable agreement between wind velocities observed with the Are&o IS radar and the I-IF radar with the SA technique at altitudes higher than 8.5-90 km, leading to the controversy on the MF/HF radar SA wind measurement. SA wind measurements with the MF radar have been compared with other techniques such as meteor radar [Stubbs, 1973; Cervena and Reid, 19951 and the UARS satellite [Burrage et al., 19961, where good agreements were found by Stubbs but the others tended to show somewhat smaller wind amplitude values of MF radar than the other techniques. Reid [1996] suggested that the argument by Hines et al. might not necessarily be valid Recent studies report wind estimation improvement by modifying the system setup [Holdsworth, 1995; Reid, 1996; Vincent et al., 1994; Igarashi, private communication,l996]. In this paper, results of the chaff (foil chaff) experiments- at 1200 and 1315 UT on 14 January 1996 at the Kagoshima Space Center (KSC), Uchinoura (31N, 131E), Japan, are compared with simultaneous ground-based observations with the CRL Yamagawa MF radar (31N, 131E) about 50 km west of KSC, and the MU radar (35N, 136E) about 600 km north-east of KSC using a meteor wind measurement mode (MU/meteor experiment). These foil chaff experiments are the first ones which were conducted successfully outside the European region. Murayama et al. [1998] also gives more results and discussions for the same observations. 575
576
Y. Murayama
et al.
EXPERIMENTS AND DATA PROCESSING For this study, we conducted two foil chaff experiments at 1200 and 1315 UT on 14 January 1997, by using two Viper III-A micro-meteorological rockets launched from KSC, Uchinoura (31N, 131E). The MU radar (35N, 136E; 600 km east of the chaff release location), and the Yamagawa MF radar (31N, 131E; 100 km west) simultaneously observed MLT wind fields. The MU radar observed meteor winds at an altitude range of 75-100 km, with time and vertical resolution of 30 min and 1 km, respectively [for the technique and details, see, e.g., Nakamura et al., 19911. The Yamagawa MF radar, operating at 1.995MHz continuously since August 1994, was observing horizontal wind velocity at the 80--100 km altitudes (night time condition) with time and vertical resolution of 2 min and 7 km, respectively [Igarashi et al., 19961. Although MF radars often operate with the vertical resolution of 3-4 km, the bandwidth and vertical resolution of our system have been limited since September 1996 to avoid interference with other communications. The foil chaff technique was developed by H.-U. Widdel of Max-Planck Institut fiir Aeronomie [e.g., Widdel, 19871 for observing wind velocity profiles at the MLT heights by employing a number of small strips of thin metalized plastic film [e.g., Widdel, 1990; von Zahn, 1987; Thrane, 19881. For our experiments foil with the 1 micrometer thickness (mass-to-area ratio =1.7 g/m*) were used for the altitude range of 80- 100 km. Each chaff strip was 25 mm long and 5 mm wide. The length is determined to be approximately half-wavelength long of the radio wave of the C-band tracking radar. 6000 strips were mounted on a rocket payload The foil strips mounted on the rocket were ejected at the altitude of about 110 km to form a chaff “cloud”, then they advected with the ambient wind motions during their descent. The location such as range, and azimuthal and elevation angles, of this chaff cloud is determined by the tracking radar. After conversion to the Cartesian coordinate system and averaging over each 300 m interval, descending speed and horizontal velocities were obtained by temporal differentiation. OBSERVED RESULTS Figure 1 shows observed wind velocities by the two chaff experiments at 1200 and 1315 UT on 14 January 1997, and hourly horizontal winds by the Yamagawa MF radar (hereafter MFR) and the MU radar (MUR), all being after the 7-km smoothing. MFR data at altitudes >86 and >88 km were missing around the two rocket experiment periods at 1200 and 1315 UT, respectively. MUR meteor observation covered the height range wider than that of the chaff experiments.
ZONAZ. 1200
COMPONENT UP
970114
MERJDIONAL 1200
COMPONENT UT 970114
ZOITAL 1315
COMPONENT UT 970114
MERIDIONAL
l.?ls
COMPONENT
UT 970114
100
100
95
-20 0 20 40 WlNIl VEXOUTY
81) 80 (m/a)
-20 0 LO 4a WIND VEu)ClTY
8Q a0 (m/s)
-20 0 20 40 WIND VEMClTY
80 80 (m/s)
-20 0 20 44 WND VELAXlTY
60 80 (m/s)
Fig. 1. Wind velocities observed by the two chaff experiments (solid) at 1200 (left two panels) and 1315 UT (right two panels ) on 14 January 1997, and hourly horizontal winds by the Yamagawa MF radar (asterisk and solid line) and the MU radar (dashed), all being after the 7-km smoothing.
MLT
Winds
by Chaff
MU-MWR / KSC CHAFF EASTWARD WIND 970114
and Radar
over Southern
Japan
MU-MIVR
NORTHWA d
KSC CHAFF WIND 970114
100 '"I"'I"'I'"k" -______.__._.._ ~.=.~.-~--=~...;._,.^.T.rr,_ -=-......--_ /q--,1 -..~.;;.,.,,-,.,,, ....----...........................~-~.~ _......‘..._..._....______ --...-- _-.-.-__---___ ._..___.........__...~....~.......----..
100
95 -2 s
*----._ cc--_-_____. ._...._.......___ -..
90
------L-"'
is E 2 85
a
10
12 14 16 8 10 14 16 U?(HR) LJT (HR) Fig. 2. Time series of the chaff (filled dot), MFR (solid line), and MUR (dashed line) wind velocity with 7-km smoothing. For vertical scale, the l-km interval corresponds to 50 m/s. The zonal component at 1200 UT at altitudes of 82-86 km shows weak eastward winds of 5-6 m/s and l-5 m/s for chaff and MFR data, respectively, while the zonal winds at 13 15 UT show velocities of O-20 m/s and l-5 m/s for chaff and MFR, respectively, at 80-86 km, For the meridional component at 1200 UT, the chaff and MFR winds at 82-86 km were northward with amplitudes of 5-25 m/s and 15-20 m/s, respectively, and at 1315 UT they were 1322 and 30-40 m/s, respectively, at SO-86 km. These results suggest that, between the chaff and MFR data, the zonal component agree well, at least in the observed height range, and the meridional component at 1200UT also agrees reasonably. However, the meridional component at 13 15 UT showed variable agreement, with difference increasing up to 50 m/s with altitude decreasing from 86 to 80 km. The MUR wind profiles showed large vertical-scale structure, and their possible temporal evolution from 1200 to 1315 UT. Time series of vertical profiles (not shown here) suggest a wave structure with the vertical scale of -20 km and the wave period of 11-14 hr, which may be a large scale gravity wave. This wave structure also can be seen in chaff profile with vertical phase shift of -5 km, implying that the same gravity wave might be detected at the two sites with a distance of 600 km. Time series of the chaff, MFR, and MUR wind velocity with 7-km smoothing are shown in Figure 2. The zonal component show very good agreement between chaff and MFR winds, with the similar values and temporal trends. The chaff meridional winds at 1200UT agreed well with MFR, but the difference of chaff-MFR values at 1315UT is again evident. SUMMARY The experimental results of the two foil chaff experiments were shown, at the Kagoshima Space Center (KSC), Uchinoura (31N, 131E), Japan. at 1200 and 1315 UT on 14 January 1996, being the first outside the European region. Observed wind velocity profiles were compared with the MU radar meteor wind (35N, 136E) and the CRL
578
Y. Murayama
et al.
Yamagawa MF radar SA winds (31N, 131E) 50 km west of KSC. The zonal component of the chaff winds generally agreed well with that of MFR winds, at the altitudes of 80-88 km, regarding height structure and temporal trends. The chaff meridional winds at 1200 UT agreed reasonably with MFR winds, while the largest difference found was 50 m/s at 80-84 km at 1315 UT. The wind fields at the two sites with the 600 km distance tended to show a coherent structure of a large scale gravity wave. ACKNOWLEDGEMENTS The Yamagawa MF radar of the CRL Yamagawa Radio Observatory was constructed with help of Drs. R. A. Vincent and I. Reid, University of Adelaide, Australia. The MU radar belongs to, and is operated by the Radio Atmospheric Science Center, Kyoto University. REFERENCES Brown, W. 0. J., MF radar interferometry, Ph.D. thesis, University of Canterbury, NZ, pp.303, 1992. Burrage, M. D., W. R. Skinner, D. A. Gell, P. B. Hays, A. R. Marshall, D. A. Chtland,A. H. Manson, S. J. Franke, D. C. Fritts, P Hoffman, C. McLandress, R. Niciejewski, F. J. Schmidlin, Ci Ci Shepherd, W. Singer, T. Tsuda, and R. A. Vincent, Validation of mesosphere and lower thermosphere winds from the high resolution Doppler imager on UARS, J. Geophys. Res., 101,10365-10392, 1996. Cervena, M. A., and I. M. Reid, Comparison of simultaneous wind measurements using colocated VHF meteor radar and MF spaced antenna radar systems, Radio Sci., 30, 1245- 126 1, 1995. Holdsworth, D. A., On the analysis of spaced sensor data, Ph.D. Thesis, University of Adelaide, Australia, 1995. Hines, C. O., Ci W. Adams, J. W. Brosnahan, F. T. Djuth, M. P. Sulzer, C. A. Tepley, and J. S. Van Baelen, Multiinstrument observations of mesospheric motions over Arecibo: comparisons and interpretations, J. Atmos. Terr. Phys., 55,241-287, 1993. Igarashi, K., I. Nishlmuta, Y. Murayama, T. Tsuda, T. Nakamura, and M. Tsutsumi, Comparison of wind measurements between Yamagawa MF radar and the MU radar, Geophys. Res. Lett., 23,3341, 1996. Manson, A. H. and C. E. Meek, Characteristics of gravity waves (10 mm-6 hours) at Saskatoon (52’N, 107’W): Observations by the phase coherent medium frequency radar, J. Geophys. Res., 98,20357-20367,1993. Murayama, Y., K. Igarashi, I. Nishimuta, R. Yamazaki, K.-I. Oyama, T. Tsuda, T. Nakamura, S. Fukao, H.-U. Wlddel, and K. Schlegel, Cooperative wind observation in the upper mesosphere and lower thermosphere with foil chaff technique, the MU radar, and Yamagawa MF radar, submitted to Earth, Planets and Space, 1998. Nakamura, T., T. Tsuda, M. Tsutsumi, K. Klta, T. Uehara, S. Kato, and S. Fukao, Meteor wind observations with the MU radar, Radio Sci., 26,857-869, 1991. Stubbs, T. J., The measurement of winds in the D-region of the ionosphere by the use of partially reflected radio waves, J. Atmos. Terr. Phys., 35,909-919, 1973. Reid, I. M., On the measurement of gravity waves, tides and mean winds in the low and middle latitude mesosphere and thermosphere with MF radar, Adv. Space Res., 18, (3)131-(3)140, 1996. Thrane, E. V., The MAC/SINE and MAC/EPSILON Campaigns, Paper presented at COSPER meeting in Espoo, Finland, to be published in Adv. Space Res., 1988. Vincent, R. A., and D. Lesicar, Dynamics of the equatorial mesosphere: First results with a new generation partial reflection radar, Geophys. Res. Lett., 18, 825-828, 1991. Vincent, R. A., D. A. Holdsworth, I. M. Reid and M. A. Cervena, Spaced antenna wind measurements: The effects of signal saturation, Proceedings of the workshop on Wind Observations in the Middle Atmosphere, Paris, 15- 18 November, 1994. Von Zahn U., J. Atmos. Terr. Phys., 49, 723-741, 1987. Widdel, H.-U., Vertical movements in the middle atmosphere derived from foil cloud experiments, J. Atmos. Terr. Phys., 49, 607, 1987. Widdel, H.-U., Foil chaff cloud as a tool for in-situ measurements of atmospheric motions in the middle atmosphere: their flight behavior and implications for radar tracking, it J. Atmos. Terr. Phys., 52, 89-101, 1990. Wu, Y.-H. and H.-U. Widdel, Saturated gravity wave spectrum in the polar summer lower thermosphere observed by foil chaff during campaign “Sodium 88”, J. Atmos. Sci., 49, 1781-1789, 1992.