Long-term observations of the wind field in the Antarctic and Arctic mesosphere and lower-thermosphere at conjugate latitudes

2011 ◽  
Vol 116 (D20) ◽  
Author(s):  
H. Iimura ◽  
D. C. Fritts ◽  
M. Tsutsumi ◽  
T. Nakamura ◽  
P. Hoffmann ◽  
...  
Keyword(s):  
Wind Field ◽  
Lower Thermosphere ◽  
Mesosphere And Lower Thermosphere ◽  
The Antarctic

Solar cycle dependence and long-term trends in the wind field of the mesosphere/lower thermosphere

1997 ◽  
Vol 59 (5) ◽  
pp. 497-509 ◽  
Author(s):  
J. Bremer ◽  
R. Schminder ◽  
K.M. Greisiger ◽  
P. Hoffmann ◽  
D. Kürschner ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Wind Field ◽  
Lower Thermosphere ◽  
Long Term Trends ◽  
Cycle Dependence

scholarly journals Climatologies and long-term changes in mesospheric wind and wave measurements based on radar observations at high and mid latitudes

2019 ◽  
Vol 37 (5) ◽  
pp. 851-875 ◽  
Author(s):  
Sven Wilhelm ◽  
Gunter Stober ◽  
Peter Brown
Keyword(s):  
Kinetic Energy ◽  
Gravity Waves ◽  
Lower Thermosphere ◽  
Atmospheric Parameters ◽  
Amplitude Response ◽  
Wave Measurements ◽  
Long Term Changes ◽  
The Mean ◽  
Mesosphere And Lower Thermosphere

Abstract. We report on long-term observations of atmospheric parameters in the mesosphere and lower thermosphere (MLT) made over the last 2 decades. Within this study, we show, based on meteor wind measurement, the long-term variability of winds, tides, and kinetic energy of planetary and gravity waves. These measurements were done between the years 2002 and 2018 for the high-latitude location of Andenes (69.3∘ N, 16∘ E) and the mid-latitude locations of Juliusruh (54.6∘ N, 13.4∘ E) and Tavistock (43.3∘ N, 80.8∘ W). While the climatologies for each location show a similar pattern, the locations differ strongly with respect to the altitude and season of several parameters. Our results show annual wind tendencies for Andenes which are toward the south and to the west, with changes of up to 3 m s−1 per decade, while the mid-latitude locations show smaller opposite tendencies to negligible changes. The diurnal tides show nearly no significant long-term changes, while changes for the semidiurnal tides differ regarding altitude. Andenes shows only during winter a tidal weakening above 90 km, while for the Canadian Meteor Orbit Radar (CMOR) an enhancement of the semidiurnal tides during the winter and a weakening during fall occur. Furthermore, the kinetic energy for planetary waves showed strong peak values during winters which also featured the occurrence of sudden stratospheric warming. The influence of the 11-year solar cycle on the winds and tides is presented. The amplitudes of the mean winds exhibit a significant amplitude response for the zonal component below 82 km during summer and from November to December between 84 and 95 km at Andenes and CMOR. The semidiurnal tides (SDTs) show a clear 11-year response at all locations, from October to November.

scholarly journals Global change induced trends in ion composition of the troposphere to the lower thermosphere

2008 ◽  
Vol 26 (5) ◽  
pp. 1181-1187 ◽  
Author(s):  
G. Beig
Keyword(s):  
Middle Atmosphere ◽  
Anthropogenic Activities ◽  
Lower Thermosphere ◽  
Cluster Ions ◽  
Atmospheric Density ◽  
Mesosphere And Lower Thermosphere ◽  
Induced Changes ◽  
Positive Ion ◽  
Mlt Region

Abstract. In this paper a brief overview of the changes in atmospheric ion compositions driven by the human-induced changes in related neutral species, and temperature from the troposphere to lower thermosphere has been made. It is found that ionic compositions undergo significant variations. The variations calculated for the double-CO2 scenario are both long-term and permanent in nature. Major neutrals which take part in the lower and middle atmospheric ion chemical schemes and undergo significant changes due to anthropogenic activities are: O, O2, H2O, NO, acetonitrile, pyridinated compounds, acetone and aerosol. The concentration of positive ion/electron density does not change appreciably in the middle atmosphere but indicates a marginal decrease above about 75 km until about 85 km, above which the magnitude of negative trend decreases and becomes negligible at 93 km. Acetonitrile cluster ions in the upper stratosphere are likely to increase, whereas NO+ and NO+(H2O) in the mesosphere and lower thermosphere (MLT) region are expected to decrease for the double CO2 scenario. It is also found that the atmospheric density of pyridinated cluster ions is fast rising in the troposphere.

A climatology of tides in the Antarctic mesosphere and lower thermosphere

2006 ◽  
Vol 111 (D23) ◽  
Author(s):  
D. J. Murphy ◽  
J. M. Forbes ◽  
R. L. Walterscheid ◽  
M. E. Hagan ◽  
S. K. Avery ◽  
...  
Keyword(s):  
Lower Thermosphere ◽  
Mesosphere And Lower Thermosphere ◽  
The Antarctic

Winds and tides of the Antarctic mesosphere and lower thermosphere: One year of meteor-radar observations over Rothera (68°S, 68°W) and comparisons with WACCM and eCMAM

2021 ◽  
Author(s):  
Shaun M Dempsey ◽  
Neil Hindley ◽  
Tracy Moffat-Griffin ◽  
Corwin Wright ◽  
Anne Smith ◽  
...  
Keyword(s):  
Planetary Wave ◽  
Lower Thermosphere ◽  
Model Development ◽  
Small Variation ◽  
Meteor Radar ◽  
Tidal Amplitude ◽  
Mesosphere And Lower Thermosphere ◽  
One Year ◽  
The Antarctic

<p>Tides are crucially important to the dynamics of the MLT. Therefore, models which aim to span the whole atmosphere must be capable of reproducing these tides, making observations of tides vital to constrain model development. Here, we present a novel climatology of 12- and 24-hour tides, measured at heights of 80–100 km by a meteor radar over the Rothera Station, Antarctica (68°S, 68°W). We use these observations to test two GCMs: WACCM and eCMAM (the latter 24-hr only). Our observations reveal large-amplitude tides with strong seasonal variability. The 12-hour tide maximises around the equinoxes and the smaller-amplitude 24-hour tide maximises in summer.<span>  </span>WACCM reproduces 12-hour tidal amplitudes at 80 km well, but not their increase with height or equinoctial maxima, and reproduces the observed small variation in 24-hr tidal amplitude with height well but with anomalously-large amplitudes. eCMAM reproduces observed 24-hr tidal amplitudes and their small variation with height. Our observations also reveal sizeable day-to-day variability in tidal amplitude at planetary wave periods, which we suggest originates from non-linear tidal/planetary-wave coupling. Furthermore, we see notable differences between observed and model background winds which are not reproduced in the models; we propose these differences may arise from the lack of in-situ gravity-wave sources in the models.</p>

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