Lidar and CTIPe model studies of the fast amplitude growth with altitude of the diurnal temperature “tides” in the Antarctic winter lower thermosphere and dependence on geomagnetic activity

2015 ◽  
Vol 42 (3) ◽  
pp. 697-704 ◽  
Author(s):  
Weichun Fong ◽  
Xinzhao Chu ◽  
Xian Lu ◽  
Cao Chen ◽  
Timothy J. Fuller-Rowell ◽  
...  
Keyword(s):  
Geomagnetic Activity ◽  
Lower Thermosphere ◽  
Diurnal Temperature ◽  
Model Studies ◽  
The Antarctic ◽  
Amplitude Growth

scholarly journals Energetic particle induced intra-seasonal variability of ozone inside the Antarctic polar vortex observed in satellite data

2015 ◽  
Vol 15 (6) ◽  
pp. 3327-3338 ◽  
Author(s):  
T. Fytterer ◽  
M. G. Mlynczak ◽  
H. Nieder ◽  
K. Pérot ◽  
M. Sinnhuber ◽  
...  
Keyword(s):  
Geomagnetic Activity ◽  
Seasonal Variability ◽  
Transport Model ◽  
Three Dimensional ◽  
Polar Vortex ◽  
Quiet Time ◽  
Significance Level ◽  
Antarctic Polar Vortex ◽  
Ap Index ◽  
The Antarctic

Abstract. Measurements from 2002 to 2011 by three independent satellite instruments, namely MIPAS, SABER, and SMR on board the ENVISAT, TIMED, and Odin satellites are used to investigate the intra-seasonal variability of stratospheric and mesospheric O3 volume mixing ratio (vmr) inside the Antarctic polar vortex due to solar and geomagnetic activity. In this study, we individually analysed the relative O3 vmr variations between maximum and minimum conditions of a number of solar and geomagnetic indices (F10.7 cm solar radio flux, Ap index, ≥ 2 MeV electron flux). The indices are 26-day averages centred at 1 April, 1 May, and 1 June while O3 is based on 26-day running means from 1 April to 1 November at altitudes from 20 to 70 km. During solar quiet time from 2005 to 2010, the composite of all three instruments reveals an apparent negative O3 signal associated to the geomagnetic activity (Ap index) around 1 April, on average reaching amplitudes between −5 and −10% of the respective O3 background. The O3 response exceeds the significance level of 95% and propagates downwards throughout the polar winter from the stratopause down to ~ 25 km. These observed results are in good qualitative agreement with the O3 vmr pattern simulated with a three-dimensional chemistry-transport model, which includes particle impact ionisation.

scholarly journals Dependence of neutral temperatures in the lower thermosphere on geomagnetic activity

2007 ◽  
Vol 112 (A6) ◽  
pp. n/a-n/a ◽  
Author(s):  
A. Aksnes ◽  
R. Eastes ◽  
S. Budzien ◽  
K. Dymond
Keyword(s):  
Geomagnetic Activity ◽  
Lower Thermosphere

scholarly journals Tropopause fold occurrence rates over the Antarctic station Troll (72° S, 2.5° E)

2013 ◽  
Vol 31 (4) ◽  
pp. 591-598 ◽  
Author(s):  
M. Mihalikova ◽  
S. Kirkwood
Keyword(s):  
Weather Forecasting ◽  
Radar Data ◽  
Occurrence Rate ◽  
High Latitudes ◽  
Global Models ◽  
Model Studies ◽  
Direct Measurements ◽  
Wind Profiler Radar ◽  
Summer Minimum ◽  
The Antarctic

Abstract. One of the important mechanisms of stratosphere–troposphere exchange, which brings ozone-rich stratospheric air to low altitudes in extratropical regions, is transport related to tropopause folds. The climatology of folds has been studied at high latitudes of the Northern Hemisphere with the help of radars and global models. Global models supply information about fold occurrence rates at high latitudes of the Southern Hemisphere as well, but so far comparisons with direct measurements are rare. The Moveable Atmospheric Radar for Antarctica (MARA), a 54.5 MHz wind-profiler radar, has been operated at the Norwegian year-round station Troll, Antarctica (72° S, 2.5° E) since December 2011. Frequent tropopause fold signatures have been observed. In this study, based on MARA observations, an occurrence rate statistics of tropopause folds from December 2011 until November 2012 has been made, and radar data have been compared with the analysis from the European Center for Medium-Range Weather Forecasting (ECMWF). The fold occurrence rates exhibit an annual cycle with winter maximum and summer minimum and suggest significantly higher occurrence rates for the given location than those obtained previously by global model studies.

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>

scholarly journals MF radar observations of the diurnal tide over Syowa, Antarctica (69° S, 40° E)

2009 ◽  
Vol 27 (7) ◽  
pp. 2653-2659 ◽  
Author(s):  
Y. Tomikawa ◽  
M. Tsutsumi
Keyword(s):  
Lower Thermosphere ◽  
Radar Data ◽  
Diurnal Tide ◽  
Syowa Station ◽  
Meridional Winds ◽  
Realistic Representation ◽  
Height Dependence ◽  
Mesosphere And Lower Thermosphere ◽  
The Antarctic ◽  
Mf Radar

Abstract. Characteristics of the diurnal tide in the Antarctic mesosphere and lower thermosphere (MLT) are investigated using 10 years of medium frequency (MF) radar data from Syowa Station (69° S, 39.6° E). Seasonal variations and height dependence of the diurnal amplitude and phase of zonal and meridional winds are mostly consistent with previous studies using the other Antarctic station data. The meridional momentum flux due to the diurnal tide shows a seasonal variation clearly different between above and below 90 km, which has never been reported in the literature. Finally, a cause of some discrepancy in the characteristics of the diurnal tide between the observation and simulation (i.e., GSWM-02) is discussed. It implies that the realistic representation of gravity waves in the simulation is crucial for realistic modeling of the diurnal tide.

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