scholarly journals Meteor radar observations of short-term tidal variabilities in the low-latitude mesosphere-lower thermosphere: Evidence for nonlinear wave-wave interactions

2008 ◽  
Vol 113 (D16) ◽  
Author(s):  
Karanam Kishore Kumar ◽  
V. Deepa ◽  
T. Maria Antonita ◽  
Geeta Ramkumar
Keyword(s):  
Nonlinear Wave ◽  
Lower Thermosphere ◽  
Meteor Radar ◽  
Short Term ◽  
Wave Interactions ◽  
Low Latitude ◽  
Radar Observations

scholarly journals Interhemispheric differences of mesosphere/lower thermosphere winds and tides investigated from three whole atmosphere models and meteor radar observations

2021 ◽  
Author(s):  
Gunter Stober ◽  
Ales Kuchar ◽  
Dimitry Pokhotelov ◽  
Huixin Liu ◽  
Han-Li Liu ◽  
...  
Keyword(s):  
General Circulation ◽  
Climate Models ◽  
Climate Model ◽  
Lower Thermosphere ◽  
Winter Season ◽  
General Circulation Models ◽  
Meteor Radar ◽  
Radar Observations ◽  
Seasonal Characteristics

Abstract. Long-term and continuous observations of mesospheric/lower thermospheric winds are rare, but they are important to investigate climatological changes at these altitudes on time scales of several years, covering a solar cycle and longer. Such long time series are a natural heritage of the mesosphere/lower thermosphere climate, and they are valuable to compare climate models or long term runs of general circulation models (GCMs). Here we present a climatological comparison of wind observations from six meteor radars at two conjugate latitudes to validate the corresponding mean winds and atmospheric diurnal and semidiurnal tides from three GCMs, namely Ground-to-Topside Model of Atmosphere and Ionosphere for Aeronomy (GAIA), Whole Atmosphere Community Climate Model Extension (Specified Dynamics) (WACCM-X(SD)) and Upper Atmosphere ICOsahedral Non-hydrostatic (UA-ICON) model. Our results indicate that there are interhemispheric differences in the seasonal characteristics of the diurnal and semidiurnal tide. There also are some differences in the mean wind climatologies of the models and the observations. Our results indicate that GAIA shows a reasonable agreement with the meteor radar observations during the winter season, whereas WACCM-X(SD) shows a better agreement with the radars for the hemispheric zonal summer wind reversal, which is more consistent with the meteor radar observations. The free running UA-ICON tends to show similar winds and tides compared to WACCM-X(SD).

scholarly journals Meteor radar observations of mesopause region long-period temperature oscillations

2016 ◽  
Vol 14 ◽  
pp. 169-174
Author(s):  
Ch. Jacobi ◽  
N. Samtleben ◽  
G. Stober
Keyword(s):  
Time Scales ◽  
Lower Thermosphere ◽  
Planetary Waves ◽  
Meteor Radar ◽  
Mesopause Region ◽  
Radar Observations ◽  
Long Period ◽  
Temperature Oscillations ◽  
Wind Measurements

Abstract. Meteor radar observations of mesosphere/lower thermosphere (MLT) daily temperatures have been performed at Collm, Germany since August 2004. The data have been analyzed with respect to long-period oscillations at time scales of 2–30 days. The results reveal that oscillations with periods of up to 6 days are more frequently observed during summer, while those with longer periods have larger amplitudes during winter. The oscillations may be considered as the signature of planetary waves. The results are compared with analyses from radar wind measurements. Moreover, the temperature oscillations show considerable year-to-year variability. In particular, amplitudes of the quasi 5-day oscillation have increased during the last decade, and the quasi 10-day oscillations are larger if the equatorial stratospheric winds are eastward.

scholarly journals Winds and tides of the Extended Unified Model in the mesosphere and lower thermosphere validated with meteor radar observations

2021 ◽  
Vol 39 (3) ◽  
pp. 487-514
Author(s):  
Matthew J. Griffith ◽  
Shaun M. Dempsey ◽  
David R. Jackson ◽  
Tracy Moffat-Griffin ◽  
Nicholas J. Mitchell
Keyword(s):  
Gravity Wave ◽  
General Circulation ◽  
Lower Thermosphere ◽  
Austral Summer ◽  
General Circulation Models ◽  
Unified Model ◽  
Climate Modelling ◽  
Meteor Radar ◽  
Radar Observations ◽  
Mesosphere And Lower Thermosphere

Abstract. The mesosphere and lower thermosphere (MLT) is a critical region that must be accurately reproduced in general circulation models (GCMs) that aim to include the coupling between the lower and middle atmosphere and the thermosphere. An accurate representation of the MLT is thus important for improved climate modelling and the development of a whole atmosphere model. This is because the atmospheric waves at these heights are particularly large, and so the energy and momentum they carry is an important driver of climatological phenomena through the whole atmosphere, affecting terrestrial and space weather. The Extended Unified Model (ExUM) is the recently developed version of the Met Office's Unified Model which has been extended to model the MLT. The capability of the ExUM to model atmospheric winds and tides in the MLT is currently unknown. Here, we present the first study of winds and tides from the ExUM. We make a comparison against meteor radar observations of winds and tides from 2006 between 80 and 100 km over two radar stations – Rothera (68∘ S, 68∘ W) and Ascension Island (8∘ S, 14∘ W). These locations are chosen to study tides in two very different tidal regimes – the equatorial regime, where the diurnal (24 h) tide dominates, and the polar regime, where the semi-diurnal (12 h) tide dominates. The results of this study illustrate that the ExUM is capable of reproducing atmospheric winds and tides that capture many of the key characteristics seen in meteor radar observations, such as zonal and meridional wind maxima and minima, the increase in tidal amplitude with increasing height, and the decrease in tidal phase with increasing height. In particular, in the equatorial regime some essential characteristics of the background winds, tidal amplitudes and tidal phases are well captured but with significant differences in detail. In the polar regime, the difference is more pronounced. The ExUM zonal background winds in austral winter are primarily westward rather than eastward, and in austral summer they are larger than observed above 90 km. The ExUM tidal amplitudes here are in general consistent with observed values, but they are also larger than observed values above 90 km in austral summer. The tidal phases are generally well replicated in this regime. We propose that the bias in background winds in the polar regime is a consequence of the lack of in situ gravity wave generation to generate eastward fluxes in the MLT. The results of this study indicate that the ExUM has a good natural capability for modelling atmospheric winds and tides in the MLT but that there is room for improvement in the model physics in this region. This highlights the need for modifications to the physical parameterization schemes used in the model in this region – such as the non-orographic spectral gravity wave scheme – to improve aspects such as polar circulation. To this end, we make specific recommendations of changes that can be implemented to improve the accuracy of the ExUM in the MLT.

scholarly journals Winds and Tides of the Extended Unified Model in the Mesosphere and Lower Thermosphere Validated with Meteor Radar Observations

2021 ◽  
Author(s):  
Matthew J. Griffith ◽  
Shaun M. Dempsey ◽  
David R. Jackson ◽  
Tracy Moffat-Griffin ◽  
Nicholas J. Mitchell
Keyword(s):  
Gravity Wave ◽  
General Circulation ◽  
Lower Thermosphere ◽  
Austral Summer ◽  
General Circulation Models ◽  
Unified Model ◽  
Climate Modelling ◽  
Meteor Radar ◽  
Radar Observations ◽  
Mesosphere And Lower Thermosphere

Abstract. The Mesosphere and Lower Thermosphere (MLT) is a critical region that must be accurately reproduced in General Circulation Models (GCMs) that aim to include the coupling between the lower & middle atmosphere and the thermosphere. An accurate representation of the MLT is important for improved climate modelling and the development of a whole atmosphere model. This is because the atmospheric waves at these heights are particularly large, and so the energy and momentum they carry is an important driver of climatological phenomena through the whole atmosphere, affecting terrestrial and space weather. The Extended Unified Model (ExUM) is the recently developed version of the Met Office's Unified Model which has been extended to model the MLT. The capability of the ExUM to model atmospheric winds and tides in the MLT is currently unknown. Here, we present the first study of winds & tides from the ExUM. We make a comparison against meteor radar observations of winds and tides from 2006 between 80 and 100 km over two radar stations – Rothera (68° S, 68° W) and Ascension Island (8° S, 14° W). These locations are chosen to study tides in two very different tidal regimes – the equatorial regime, where the diurnal (24 hour) tide dominates, and the polar regime, where the semi-diurnal (12 hour) tide dominates. The results of this study illustrate that the ExUM is capable of reproducing atmospheric winds and tides that capture many of the key characteristics seen in meteor radar observations, such as zonal & meridional wind maxima and minima, the increase in tidal amplitude with increasing height, and the decrease in tidal phase with increasing height. In particular, in the equatorial regime some essential characteristics of the background winds, tidal amplitudes and tidal phases are well captured, but with significant differences in detail. In the polar regime, the difference is more pronounced. The ExUM zonal background winds in austral winter are primarily eastward rather than westward, and in austral summer are larger than observed above 90 km. The ExUM tidal amplitudes here are in general consistent with observed values, but are also larger than observed values above 90 km in austral summer. The tidal phases are generally well replicated in this regime. We propose that the bias in background winds in the polar regime is a consequence of the lack of in-situ gravity wave generation to generate eastward fluxes in the MLT. The results of this study indicate that the ExUM has a good natural capability for modelling atmospheric winds and tides in the MLT, but that there is room for improvement in the model physics in this region. This highlights the need for modifications to the physical parameterization schemes used in the model in this region – such as the non-orographic spectral gravity wave scheme – to improve aspects such as polar circulation. To this end, we make specific recommendations of changes that can be implemented to improve the accuracy of the ExUM in the MLT.

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