Radar observations of prevailing winds and waves in the Southern Hemisphere mesosphere and lower thermosphere

1989 ◽  
Vol 130 (2-3) ◽  
pp. 303-318 ◽  
Author(s):  
A. Phillips ◽  
R. A. Vincent
Keyword(s):  
Southern Hemisphere ◽  
Lower Thermosphere ◽  
Radar Observations ◽  
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

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.

MF radar observations of 6.5-day wave in the equatorial mesosphere and lower thermosphere

2004 ◽  
Vol 66 (6-9) ◽  
pp. 507-515 ◽  
Author(s):  
P. Kishore ◽  
S.P. Namboothiri ◽  
K. Igarashi ◽  
S. Gurubaran ◽  
S. Sridharan ◽  
...  
Keyword(s):  
Lower Thermosphere ◽  
Radar Observations ◽  
Mesosphere And Lower Thermosphere ◽  
Mf Radar

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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