scholarly journals Seasonal variability of atmospheric tides in the mesosphere and lower thermosphere: meteor radar data and simulations

2018 ◽  
Vol 36 (3) ◽  
pp. 825-830 ◽  
Author(s):  
Dimitry Pokhotelov ◽  
Erich Becker ◽  
Gunter Stober ◽  
Jorge L. Chau
Keyword(s):  
Seasonal Variability ◽  
Lower Thermosphere ◽  
Circulation Model ◽  
Radar Data ◽  
Atmospheric Tides ◽  
Northern Germany ◽  
Model Driven ◽  
Resolution Model ◽  
Mesosphere And Lower Thermosphere ◽  
Thermal Tides

Abstract. Thermal tides play an important role in the global atmospheric dynamics and provide a key mechanism for the forcing of thermosphere–ionosphere dynamics from below. A method for extracting tidal contributions, based on the adaptive filtering, is applied to analyse multi-year observations of mesospheric winds from ground-based meteor radars located in northern Germany and Norway. The observed seasonal variability of tides is compared to simulations with the Kühlungsborn Mechanistic Circulation Model (KMCM). It is demonstrated that the model provides reasonable representation of the tidal amplitudes, though substantial differences from observations are also noticed. The limitations of applying a conventionally coarse-resolution model in combination with parametrisation of gravity waves are discussed. The work is aimed towards the development of an ionospheric model driven by the dynamics of the KMCM.

scholarly journals Seasonal variability of atmospheric tides in the mesosphere and lower thermosphere: meteor radar data and simulations

2018 ◽  
Author(s):  
Dimitry Pokhotelov ◽  
Erich Becker ◽  
Gunter Stober ◽  
Jorge L. Chau
Keyword(s):  
Seasonal Variability ◽  
Lower Thermosphere ◽  
Circulation Model ◽  
Radar Data ◽  
Atmospheric Tides ◽  
Model Driven ◽  
Resolution Model ◽  
Novel Method ◽  
Mesosphere And Lower Thermosphere ◽  
Thermal Tides

Abstract. Thermal tides play an important role in the global atmospheric dynamics and provide a key mechanism for the forcing of thermosphere/ionosphere dynamics from below. A novel method for extracting tidal contributions, based on the adaptive filtering, is applied to analyse multi-year observations of mesospheric winds from ground-based meteor radars located in Northern Germany and Norway. The observed seasonal variability of tides is compared to simulations with the Kühlungsborn Mechanistic Circulation Model (KMCM). It is demonstrated that the model provides reasonable representation of the tidal amplitudes. The limitations of applying a conventionally coarse resolution model in combination with parametrisation of gravity waves are discussed. The work is aimed towards the development of an ionospheric model driven by the dynamics of the KMCM.

scholarly journals The wintertime two-day wave in the polar stratosphere, mesosphere and lower thermosphere

2008 ◽  
Vol 8 (3) ◽  
pp. 749-755 ◽  
Author(s):  
D. J. Sandford ◽  
M. J. Schwartz ◽  
N. J. Mitchell
Keyword(s):  
Lower Thermosphere ◽  
Radar Data ◽  
The Arctic ◽  
Horizontal Wind ◽  
Meteor Radar ◽  
Polar Night ◽  
Zonal Wavenumber ◽  
Mesosphere And Lower Thermosphere ◽  
Polar Stratosphere ◽  
Striking Contrast

Abstract. Recent observations of the polar mesosphere have revealed that waves with periods near two days reach significant amplitudes in both summer and winter. This is in striking contrast to mid-latitude observations where two-day waves maximise in summer only. Here, we use data from a meteor radar at Esrange (68° N, 21° E) in the Arctic and data from the MLS instrument aboard the EOS Aura satellite to investigate the wintertime polar two-day wave in the stratosphere, mesosphere and lower thermosphere. The radar data reveal that mesospheric two-day wave activity measured by horizontal-wind variance has a semi-annual cycle with maxima in winter and summer and equinoctial minima. The MLS data reveal that the summertime wave in the mesosphere is dominated by a westward-travelling zonal wavenumber three wave with significant westward wavenumber four present. It reaches largest amplitudes at mid-latitudes in the southern hemisphere. In the winter polar mesosphere, however, the wave appears to be an eastward-travelling zonal wavenumber two, which is not seen during the summer. At the latitude of Esrange, the eastward-two wave reaches maximum amplitudes near the stratopause and appears related to similar waves previously observed in the polar stratosphere. We conclude that the wintertime polar two-day wave is the mesospheric manifestation of an eastward-propagating, zonal-wavenumber-two wave originating in the stratosphere, maximising at the stratopause and likely to be generated by instabilities in the polar night jet.

scholarly journals Analysis of Migrating and Non-Migrating Tides of the Extended Unified Model in the Mesosphere and Lower Thermosphere

2021 ◽  
Author(s):  
Matthew J. Griffith ◽  
Nicholas J. Mitchell
Keyword(s):  
Lower Thermosphere ◽  
Unified Model ◽  
Atmospheric Tides ◽  
Global Circulation ◽  
Global Circulation Models ◽  
Depth Analysis ◽  
Mesosphere And Lower Thermosphere ◽  
Temporal Modes ◽  
Energy And Momentum ◽  
Rich Spectrum

Abstract. Atmospheric tides play a key role in coupling the lower, middle and upper atmosphere/ionosphere. The tides reach large amplitudes in the Mesosphere and Lower Thermosphere (MLT) where they can have significant fluxes of energy and momentum and so strongly influence the coupling and dynamics. The tides must therefore be accurately represented in Global Circulation Models (GCMs) that seek to model the coupling of atmospheric layers and impacts on the ionosphere. The tides consist of both migrating (sun-following) and non-migrating (not sun-following) components, both of which have important influences on the atmosphere. The Extended Unified Model (ExUM) is a recently developed version of the Met Office's Unified Model GCM which has been extended to include the MLT. Here, we present the first in-depth analysis of migrating and non-migrating modes in the ExUM. We show that the ExUM produces both non-migrating and migrating tides in the MLT of significant amplitude across a rich spectrum of spatial and temporal modes. The dominant non-migrating modes in the MLT are found to be the DE3, DW2 and DW3 in the diurnal tide and the S0, SW1 and SW3 in the semidiurnal tide. These modes can have monthly mean amplitudes at a height of 95 km as large as 35 ms−1 / 10 K. All the non-migrating modes exhibit a strong seasonal variability in amplitude and significant short-term variability is evident. Both the migrating and non-migrating modes exhibit notable variation with latitude. For example, the temperature and wind diurnal tides maximise at low latitudes and the semidiurnal tides include maxima at high latitudes. Our results demonstrate the capability of the ExUM for modelling atmospheric migrating and non-migrating tides and lays the foundation for its future development into a whole atmosphere model. To this end, we make specific recommendations on further developments which would improve the capability of the model.

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.

The first observation of the atmospheric tides in the mesosphere and lower thermosphere over Hainan, China

2010 ◽  
Vol 55 (11) ◽  
pp. 1059-1066 ◽  
Author(s):  
GuoYing Jiang ◽  
JiYao Xu ◽  
JianKui Shi ◽  
GuoTao Yang ◽  
Xiao Wang ◽  
...  
Keyword(s):  
Lower Thermosphere ◽  
Atmospheric Tides ◽  
Mesosphere And Lower Thermosphere

scholarly journals The wintertime two-day wave in the Polar Stratosphere, Mesosphere and lower Thermosphere

2007 ◽  
Vol 7 (5) ◽  
pp. 14747-14765
Author(s):  
D. J. Sandford ◽  
M. J. Schwartz ◽  
N. J. Mitchell
Keyword(s):  
Lower Thermosphere ◽  
Radar Data ◽  
The Arctic ◽  
Horizontal Wind ◽  
Meteor Radar ◽  
Polar Night ◽  
Zonal Wavenumber ◽  
Mesosphere And Lower Thermosphere ◽  
Polar Stratosphere ◽  
Striking Contrast

Abstract. Recent observations of the polar mesosphere have revealed that waves with periods near two days reach significant amplitudes in both summer and winter. This is in striking contrast to mid-latitude observations where two-day waves maximise in summer only. Here, we use data from a meteor radar at Esrange (68° N, 21° E) in the Arctic and data from the MLS instrument aboard the EOS Aura satellite to investigate the wintertime polar two-day wave in the stratosphere, mesosphere and lower thermosphere. The radar data reveal that mesospheric two-day wave activity measured by horizontal-wind variance has a semi-annual cycle with maxima in winter and summer and equinoctial minima. The MLS data reveal that the summertime wave in the mesosphere is dominated by a westward-travelling zonal wavenumber three wave with significant westward wavenumber four present. It reaches largest amplitudes at mid-latitudes in the southern hemisphere. In the winter polar mesosphere, however, the wave appears to be an eastward-travelling zonal wavenumber two, which is not seen during the summer. At the latitude of Esrange, the eastward-two wave reaches maximum amplitudes near the stratopause and appears related to similar waves previously observed in the polar stratosphere. We conclude that the wintertime polar two-day wave is the mesospheric manifestation of an eastward-propagating, zonal-wavenumber-two wave originating in the stratosphere, maximising at the stratopause and likely to be generated by instabilities in the polar night jet.

scholarly journals Diurnal tidal variability in the upper mesosphere and lower thermosphere

1997 ◽  
Vol 15 (9) ◽  
pp. 1176-1186 ◽  
Author(s):  
M. E. Hagan ◽  
C. McLandress ◽  
J. M. Forbes
Keyword(s):  
Heat Source ◽  
Latent Heat ◽  
Seasonal Variability ◽  
Lower Thermosphere ◽  
Wave Model ◽  
Global Scale ◽  
Horizontal Wind ◽  
Boreal Winter ◽  
Tidal Effects ◽  
Mesosphere And Lower Thermosphere

Abstract. We explore tropospheric latent heat release as a source of variability of the diurnal tide in the mesosphere and lower thermosphere (MLT) in two ways. First, we present analyses of the UARS WINDII horizontal wind data, which reveal signatures of nonmigrating tidal effects as large as 25 m/s during both vernal equinox and boreal winter. These effects are of greater relative importance during the latter season. Complementary global-scale wave model (GSWM) results which account for a tropospheric latent heat source generally underestimate the observed nonmigrating tidal effects but capture the seasonal variability that is observed. Second, we pursue a new parameterization scheme to investigate seasonal variability of the migrating diurnal tidal component of the latent heat source with GSWM. These results confirm previously reported seasonal trends, but suggest that the MLT effects may be as much as an order of magnitude larger than earlier predictions.

scholarly journals First results from the CAWSES-India Tidal Campaign

2008 ◽  
Vol 26 (8) ◽  
pp. 2323-2331 ◽  
Author(s):  
S. Gurubaran ◽  
D. Narayana Rao ◽  
G. Ramkumar ◽  
T. K. Ramkumar ◽  
G. Dutta ◽  
...  
Keyword(s):  
Lower Thermosphere ◽  
Weather Data ◽  
Atmospheric Tides ◽  
Data Sets ◽  
Low Latitude ◽  
First Results ◽  
Mesosphere And Lower Thermosphere ◽  
Nonmigrating Tides ◽  
The Western Pacific ◽  
Mlt Region

Abstract. The first CAWSES-India Tidal Campaign was conducted by the Indian scientific community during March–April 2006. The objectives of this campaign were: (1) To determine the characteristics of tides in the troposphere and lower stratosphere (0–20 km) and mesosphere and lower thermosphere (MLT) region (80–100 km), (2) to explore and identify what lower atmospheric processes drive middle atmospheric tides in the Indian continental region and (3) to provide information on those short-term variabilities of MLT tides that are likely to have an impact on the ionospheric variabilities and contribute to the upper atmospheric weather. Data sets from experiments conducted at the three low latitude radar sites, namely, Trivandrum (8.5° N, 76.9° E), Tirunelveli (8.7° N, 77.8° E) and Gadanki (13.5° N, 79.2° E) and fortnightly rocket launches from Thumba were made use of in this study. An important observational finding reported in this work is that the radar observations at Tirunelveli/Trivandrum indicate the presence of 15–20 day modulation of diurnal tide activity at MLT heights during the February–March period. A similar variation in the OLR fields in the western Pacific (120–160° longitude region) suggests a possible link between the observed tidal variabilities and the variations in the deep tropical convection through the nonmigrating tides it generates.

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