scholarly journals Planetary waves and variability of the semidiurnal tide in the mesosphere and lower thermosphere over Esrange (68°N, 21°E) during winter

2004 ◽  
Vol 109 (A8) ◽  
Author(s):  
Dora V. Pancheva
Keyword(s):  
Lower Thermosphere ◽  
Planetary Waves ◽  
Semidiurnal Tide ◽  
Mesosphere And Lower Thermosphere

The coupling of planetary waves, tides and gravity waves in the mesosphere and lower thermosphere

1999 ◽  
Vol 24 (11) ◽  
pp. 1571-1576 ◽  
Author(s):  
P.J.S. Williams ◽  
N.J. Mitchell ◽  
A.G. Beard ◽  
V.St.C. Howells ◽  
H.G. Muller
Keyword(s):  
Gravity Waves ◽  
Lower Thermosphere ◽  
Planetary Waves ◽  
Mesosphere And Lower Thermosphere

scholarly journals Mean winds, temperatures and the 16- and 5-day planetary waves in the mesosphere and lower thermosphere over Bear Lake Observatory (42° N, 111° W)

2012 ◽  
Vol 12 (3) ◽  
pp. 1571-1585 ◽  
Author(s):  
K. A. Day ◽  
M. J. Taylor ◽  
N. J. Mitchell
Keyword(s):  
Zonal Wind ◽  
Lower Thermosphere ◽  
Planetary Waves ◽  
Zonal Winds ◽  
Annual Variability ◽  
Bear Lake ◽  
Meridional Winds ◽  
The Mean ◽  
Mesosphere And Lower Thermosphere ◽  
Wind Shears

Abstract. Atmospheric temperatures and winds in the mesosphere and lower thermosphere have been measured simultaneously using the Aura satellite and a meteor radar at Bear Lake Observatory (42° N, 111° W), respectively. The data presented in this study is from the interval March 2008 to July 2011. The mean winds observed in the summer-time over Bear Lake Observatory show the meridional winds to be equatorward at meteor heights during April−August and to reach monthly-mean velocities of −12 m s−1. The mean winds are closely related to temperatures in this region of the atmosphere and in the summer the coldest mesospheric temperatures occur about the same time as the strongest equatorward meridional winds. The zonal winds are eastward through most of the year and in the summer strong eastward zonal wind shears of up to ~4.5 m s−1 km−1 are present. However, westward winds are observed at the upper heights in winter and sometimes during the equinoxes. Considerable inter-annual variability is observed in the mean winds and temperatures. Comparisons of the observed winds with URAP and HWM-07 reveal some large differences. Our radar zonal wind observations are generally more eastward than predicted by the URAP model zonal winds. Considering the radar meridional winds, in comparison to HWM-07 our observations reveal equatorward flow at all meteor heights in the summer whereas HWM-07 suggests that only weakly equatorward, or even poleward flows occur at the lower heights. However, the zonal winds observed by the radar and modelled by HWM-07 are generally similar in structure and strength. Signatures of the 16- and 5-day planetary waves are clearly evident in both the radar-wind data and Aura-temperature data. Short-lived wave events can reach large amplitudes of up to ~15 m s−1 and 8 K and 20 m s−1 and 10 K for the 16- and 5-day waves, respectively. A clear seasonal and short-term variability are observed in the 16- and 5-day planetary wave amplitudes. The 16-day wave reaches largest amplitude in winter and is also present in summer, but with smaller amplitudes. The 5-day wave reaches largest amplitude in winter and in late summer. An inter-annual variability in the amplitude of the planetary waves is evident in the four years of observations. Some 41 episodes of large-amplitude wave occurrence are identified. Temperature and wind amplitudes for these episodes, AT and AW, that passed the Student T-test were found to be related by, AT = 0.34 AW and AT = 0.62 AW for the 16- and 5-day wave, respectively.

Height-latitude structure of the vertical component of the migrating semidiurnal tide in the upper mesosphere and lower thermosphere region (80–100 km)

2011 ◽  
Vol 47 (1) ◽  
pp. 108-118 ◽  
Author(s):  
Yu. I. Portnyagin ◽  
E. G. Merzlyakov ◽  
T. V. Solov’eva ◽  
A. I. Pogorel’tsev ◽  
E. V. Suvorova ◽  
...  
Keyword(s):  
Lower Thermosphere ◽  
Vertical Component ◽  
Semidiurnal Tide ◽  
Mesosphere And Lower Thermosphere

Radar observations of the semidiurnal tide in the mesosphere and lower thermosphere at midlatitudes

1994 ◽  
Vol 56 (10) ◽  
pp. 1251-1261 ◽  
Author(s):  
J.E. Salah ◽  
R.R. Clark ◽  
J.M. Forbes ◽  
A.H. Manson ◽  
S.K. Avery ◽  
...  
Keyword(s):  
Lower Thermosphere ◽  
Semidiurnal Tide ◽  
Radar Observations ◽  
Mesosphere And Lower Thermosphere

Influence of geomagnetic disturbances on midlatitude mesosphere/lower thermosphere mean winds and tides 

2021 ◽  
Author(s):  
Christoph Jacobi ◽  
Friederike Lilienthal ◽  
Dmitry Korotyshkin ◽  
Evgeny Merzlyakov ◽  
Gunter Stober
Keyword(s):  
Lower Thermosphere ◽  
Meridional Wind ◽  
Vertical Profiles ◽  
Semidiurnal Tide ◽  
Geomagnetic Disturbances ◽  
Noticeable Effect ◽  
Zonal Winds ◽  
The Mean ◽  
Mesosphere And Lower Thermosphere ◽  
Midlatitude Mesosphere

<p>Observations of upper mesosphere/lower thermosphere (MLT) wind have been performed at Collm (51°N, 13°E) and Kazan (56°N, 49°E), using two SKiYMET all-sky meteor radars with similar configuration. Daily vertical profiles of mean winds and tidal amplitudes have been constructed from hourly horizontal winds. We analyze the response of mean winds and tidal amplitudes to geomagnetic disturbances. To this end we compare winds and amplitudes for very quiet (Ap ≤ 5) and unsettled/disturbed (Ap ≥ 20) geomagnetic conditions. Zonal winds in both the mesosphere and lower thermosphere are weaker during disturbed conditions for both summer and winter. The summer equatorward meridional wind jet is weaker for disturbed geomagnetic conditions. Tendencies over Collm and Kazan for geomagnetic effects on mean winds qualitatively agree during most of the year. For the diurnal tide, amplitudes in summer are smaller in the mesosphere but greater in the lower thermosphere, but no clear tendency is seen for winter. Semidiurnal tidal amplitudes increase during geomagnetic active days in summer and winter. Terdiurnal amplitudes are slightly reduced in the mesosphere during disturbed days, but no clear effect is visible for the lower thermosphere. Overall, while there is a noticeable effect of geomagnetic variability on the mean wind, the effect on tidal amplitudes, except for the semidiurnal tide, is relatively small and partly different over Collm and Kazan.</p>

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