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Atmosphere
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Structure and Dynamics of Mesosphere and Lower Thermosphere
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Structure and Dynamics of Mesosphere and Lower Thermosphere

A special issue of Atmosphere (ISSN 2073-4433). This special issue belongs to the section "Upper Atmosphere".

Deadline for manuscript submissions: closed (6 September 2023) | Viewed by 14584

Special Issue Editors

Dr. Shengyang Gu

E-Mail Website
Guest Editor
Electronic Information School, Wuhan University, Wuhan 430072, China
Interests: middle- and upper-atmosphere dynamics; mesosphere/ionosphere coupling; near-space optical detection; spaceborne detection technology
Dr. Kaiming Huang

E-Mail Website
Guest Editor
Electronic Information School, Wuhan University, Wuhan 430072, China
Interests: atmospheric physics; atmospheric dynamics; atmospheric remote sensing
Dr. Chengyun Yang

E-Mail Website
Guest Editor
School of Earth and Space Science, University of Science and Technology of China, Hefei 230026, China
Interests: atmospheric physics; atmospheric dynamics; ocean/middle atmosphere coupling; atmospheric tide

Special Issue Information

Dear Colleagues,

The mesosphere and lower thermosphere (MLT) region is an area where the lower atmosphere extends to outer space, with significant impacts from both below and above. On the one hand, the upward propagation of gravity waves, tides, and planetary waves in this region extract energy during their amplification through wave–mean interaction. On the other hand, the wave breaking also deposits energy into the background. This makes the structure of the MLT atmosphere variable and deviates from its equilibrium state. For example, the sudden stratospheric event, which is related to the rapid growth of planetary waves, has been proven to have a dramatic impact on the dynamical process in the MLT region. With the help of TIMED and Aura satellite observations, as well as numerical data assimilation, our knowledge about the structure of the MLT region has expanded greatly during the past twenty years. However, many aspects of the MLT region are still mysterious compared to the lower atmosphere.

We invite you to submit your research for publication in this Special Issue, which aims to improve the understanding on the structure of the mesosphere and lower thermosphere. Both original research and review papers are welcome. We encourage contributions to topics including but not limited to:

  • Observations and assimilation results on the mesosphere and lower thermosphere;
  • Wave activities in the mesosphere and lower thermosphere;
  • Vertical and interhemispheric couplings in the MLT region;
  • Variations of the mesosphere and lower thermosphere due to lower atmospheric forcing such as SSW, ENSO, and MJO;
  • Influence of solar and geomagnetic activities on the mesosphere and lower thermosphere.

Dr. Shengyang Gu
Dr. Kaiming Huang
Dr. Chengyun Yang
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Atmosphere is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • mesosphere and lower thermosphere
  • dynamics
  • structure
  • wave activities
  • observations and data assimilation
  • vertical and interhemispheric coupling

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Published Papers (6 papers)

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17 pages, 570 KiB  
Article
Modelling of Energy-Dependent Electron Interactions in the Earth’s Mesosphere
by Laurence Campbell and Michael J. Brunger
Atmosphere 2023, 14(4), 611; https://doi.org/10.3390/atmos14040611 - 23 Mar 2023
Viewed by 1454
Abstract
Electrons are produced in the Earth’s quiet nighttime mesosphere by ionization by cosmic rays and ionization of NO by Lyman-α radiation. They are removed by attachment or recombination processes that are usually assumed in modelling to occur at the ambient temperature. However, [...] Read more.
Electrons are produced in the Earth’s quiet nighttime mesosphere by ionization by cosmic rays and ionization of NO by Lyman-α radiation. They are removed by attachment or recombination processes that are usually assumed in modelling to occur at the ambient temperature. However, the electrons have initial energies that are much higher than at thermal equilibrium, and so must have a range of energies as they progress towards equilibrium via interactions with atoms and molecules. As attachment and recombination rates are dependent on the electron energy, it is possible that modelling that considers the actual energy of the electrons will give different results to those based on assuming that the electrons are at the ambient temperature. In this work, starting with electrons at a higher initial energy, the detailed electron interactions (including elastic scattering and vibrational excitation of molecules) are tracked in a time-step simulation. This simulation is implemented by treating electrons in subranges of the electron energy spectrum as chemical species. This allows an investigation of two phenomena in the nighttime mesosphere: the origin of the D-region ledge and the production of radiative emissions from vibrationally excited molecules. It is found that there is negligible difference in the electron densities calculated using the ambient temperature or detailed interaction models, so this study does not provide an explanation for the D-region ledge. However, in the latter model, emissions at various wavelengths are predicted due to reactions involving vibrationally excited molecules. It is also found, using the time-step calculation, that it would take several hours for the predicted electron density to approach equilibrium. Full article
(This article belongs to the Special Issue Structure and Dynamics of Mesosphere and Lower Thermosphere)
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16 pages, 4882 KiB  
Article
Seismo Ionospheric Anomalies around and over the Epicenters of Pakistan Earthquakes
by Munawar Shah, Rasim Shahzad, Muhsan Ehsan, Bushra Ghaffar, Irfan Ullah, Punyawi Jamjareegulgarn and Ahmed M. Hassan
Atmosphere 2023, 14(3), 601; https://doi.org/10.3390/atmos14030601 - 22 Mar 2023
Cited by 10 | Viewed by 3410
Abstract
Global Navigation Satellite System (GNSS)-based ionospheric anomalies are nowadays used to identify a possible earthquake (EQ) precursor and hence a new research topic in seismic studies. The current study also aims to provide an investigation of ionospheric anomalies associated to EQs. In order [...] Read more.
Global Navigation Satellite System (GNSS)-based ionospheric anomalies are nowadays used to identify a possible earthquake (EQ) precursor and hence a new research topic in seismic studies. The current study also aims to provide an investigation of ionospheric anomalies associated to EQs. In order to study possible pre-and post-seismic perturbations during the preparation phase of large-magnitude EQs, statistical and machine learning algorithms are applied to Total Electron Content (TEC) from the Global Positioning System (GPS) and Global Ionosphere Maps (GIMs). We observed TEC perturbation from the Sukkur (27.8° N, 68.9° E) GNSS station near the epicenter of Mw 5.4 Mirpur EQ within 5–10 days before the main shock day by implementing machine learning and statistical analysis. However, no TEC anomaly occurred in GIM-TEC over the Mirpur EQ epicenter. Furthermore, machine learning and statistical techniques are also implemented on GIM TEC data before and after the Mw 7.7 Awaran, where TEC anomalies can be clearly seen within 5–10 days before the seismic day and the subsequent rise in TEC during the 2 days after the main shock. These variations are also evident in GIM maps over the Awaran EQ epicenter. The findings point towards a large emission of EQ energy before and after the main shock during quiet storm days, which aid in the development of lithosphere ionosphere coupling. However, the entire analysis can be expanded to more satellite and ground-based measurements in Pakistan and other countries to reveal the pattern of air ionization from the epicenter through the atmosphere to the ionosphere. Full article
(This article belongs to the Special Issue Structure and Dynamics of Mesosphere and Lower Thermosphere)
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13 pages, 4586 KiB  
Article
Thermospheric NO Cooling during an Unusual Geomagnetic Storm of 21–22 January 2005: A Comparative Study between TIMED/SABER Measurements and TIEGCM Simulations
by Tikemani Bag, Diptiranjan Rout, Yasunobu Ogawa and Vir Singh
Atmosphere 2023, 14(3), 556; https://doi.org/10.3390/atmos14030556 - 14 Mar 2023
Cited by 7 | Viewed by 1804
Abstract
The geomagnetic storm is the manifestation of the solar wind–magnetosphere interaction. It deposits huge amount of the solar energy into the magnetosphere–ionosphere–thermosphere (MIT) system. This energy creates global perturbations in the chemistry, dynamics, and energetics of the MIT system. The high latitude energy [...] Read more.
The geomagnetic storm is the manifestation of the solar wind–magnetosphere interaction. It deposits huge amount of the solar energy into the magnetosphere–ionosphere–thermosphere (MIT) system. This energy creates global perturbations in the chemistry, dynamics, and energetics of the MIT system. The high latitude energy deposition results in the Joule and particle heating that subsequently increases the thermospheric temperature. The thermospheric temperature is effectively regulated by the process of thermospheric cooling emission by nitric oxide via 5.3 µm. A peculiar, intense geomagnetic storm (Dst = −105 nT) occurred during 21–22 January 2005, where the main phase developed during the northward orientation of the z-component of interplanetary magnetic field. We utilized the nitric oxide 5.3 µm infrared emission from the NCAR’s Thermosphere–Ionosphere–Electrodynamics General Circulation Model (TIEGCM) simulation and the Sounding of Atmosphere using Broadband Emission Radiometry (SABER) onboard the thermosphere–ionosphere–mesosphere energetic and dynamics satellite to investigate its response to this anomalous geomagnetic storm. We compared the model results with the observations on both the local and global scales. It is observed that the model results agree very well with the observations during quiet times. However, the model severely underestimates the cooling emission by one-fourth of the observations, although it predicts an enhancement in the thermospheric temperature and densities of atomic oxygen and nitric oxide during the geomagnetic storm. Full article
(This article belongs to the Special Issue Structure and Dynamics of Mesosphere and Lower Thermosphere)
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21 pages, 5396 KiB  
Article
Short-Term Prediction of 80–88 km Wind Speed in Near Space Based on VMD–PSO–LSTM
by Shaoyi Yang, Hua Yang, Na Li and Zonghua Ding
Atmosphere 2023, 14(2), 315; https://doi.org/10.3390/atmos14020315 - 4 Feb 2023
Cited by 10 | Viewed by 2628
Abstract
The accurate prediction of atmospheric wind speed in near space is of importance for both middle and upper atmospheric scientific research and engineering applications. In order to improve the accuracy of short-term wind speed predictions in near space, this paper proposes a multi-step [...] Read more.
The accurate prediction of atmospheric wind speed in near space is of importance for both middle and upper atmospheric scientific research and engineering applications. In order to improve the accuracy of short-term wind speed predictions in near space, this paper proposes a multi-step hybrid prediction method based on the combination of variational modal decomposition (VMD), particle swarm optimization (PSO) and long short-term memory neural networks (LSTM). This paper uses the measurement of wind speed in the height range of 80–88 km at the Kunming site (25.6° N, 103.8° E) for wind speed prediction experiments. The results show that the root mean square error (RMSE) and the mean absolute percentage error (MAPE) of multi–step wind predictions are less than 6 m/s and 15%, respectively. Furthermore, the proposed VMD–PSO–LSTM method is compared with the traditional seasonal difference autoregressive sliding average model (SARIMA) to investigate its performance. Our analysis shows that the percentage improvement of prediction performance compared to the traditional time series prediction model can reach at most 85.21% and 83.75% in RMSE and MAPE, respectively, which means that the VMD–PSO–LSTM model has better accuracy in the multi-step prediction of the wind speed. Full article
(This article belongs to the Special Issue Structure and Dynamics of Mesosphere and Lower Thermosphere)
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18 pages, 5372 KiB  
Article
Tidal Structures in the Mesosphere and Lower Thermosphere and Their Solar Cycle Variations
by Ruidi Sun, Shengyang Gu, Xiankang Dou and Na Li
Atmosphere 2022, 13(12), 2036; https://doi.org/10.3390/atmos13122036 - 4 Dec 2022
Cited by 6 | Viewed by 2358
Abstract
We studied the correlations between the migrating and non-migrating tides and solar cycle in the mesosphere and lower thermosphere (MLT) regions between 60° S and 60° N, which are in LAT-LON Earth coordinates, by analyzing the simulation datasets from [...] Read more.
We studied the correlations between the migrating and non-migrating tides and solar cycle in the mesosphere and lower thermosphere (MLT) regions between 60° S and 60° N, which are in LAT-LON Earth coordinates, by analyzing the simulation datasets from the thermosphere and ionosphere extension of the Whole Atmosphere Community Climate Model (WACCM-X). A least squares fitting method was utilized to obtain the daily mean migrating tides and non-migrating tides. The Pearson linear correlation coefficient was used to analyze the correlations between tides and solar activity. Our analysis shows that the negative correlations between tides and solar activity are mostly impacted by the first symmetrical structure of the tidal modes for both migrating and non-migrating components. The coefficient of molecular thermal conductivity for the first symmetrical structure is small at low solar flux, so the tides dissipate more slowly when the F10.7 cm radio flux level is low. Thus, the amplitudes of tidal variations under a solar minimum condition are larger than those under a solar maximum condition. The correlation between tides and solar activity could also be influenced by some other factors, such as geomagnetic activity and the density of carbon dioxide  CO2 on Earth. The tidal variations can be influenced by westward background wind, which grows stronger as geomagnetic activity rises. Further, dissipation of the tides decreases because the heat conduction and molecular viscosity are weakened in the cooling thermosphere caused by increasing CO2, which results in larger tidal amplitudes under the solar maximum condition. It is found that the correlations between tides and solar cycle vary at different altitudes and latitudes. The negative correlations are most possibly influenced by the first symmetrical structure of tidal variations and may also be impacted by geomagnetic activity. The positive correlations are impacted by the density of CO2. Full article
(This article belongs to the Special Issue Structure and Dynamics of Mesosphere and Lower Thermosphere)
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10 pages, 3739 KiB  
Technical Note
Influence of Meteor Count on Wind Field Retrieved by All-Sky Meteor Radar
by Xiaojing Hao, Yu Ma, Zonghua Ding, Libin Wang, Na Li and Jinsong Chen
Atmosphere 2023, 14(3), 519; https://doi.org/10.3390/atmos14030519 - 8 Mar 2023
Viewed by 1418
Abstract
The all-sky meteor radar is an important means to detect 70–110 km wind fields. Previous studies have shown that the wind field retrieved by all-sky meteor radars is closely related to the meteor count detected by the radar. However, the precision of the [...] Read more.
The all-sky meteor radar is an important means to detect 70–110 km wind fields. Previous studies have shown that the wind field retrieved by all-sky meteor radars is closely related to the meteor count detected by the radar. However, the precision of the wind field is still unclear. In this paper, the influence of the meteor counts detected by two all-sky meteor radars operating simultaneously at Kunming station on wind fields is analyzed based on the observations of the two radars from 1 November 2013 to 31 December 2014. First, the meteor counts detected by the two meteor radars are approximately 100–3000 per hour, and the meteor count detected by the 37.5 MHz meteor radar is more than that according to the 53.1 MHz meteor radar. The meteor counts detected by the two radars vary with the local time and altitude. The meteor counts detected from 20 UTC to 02 UTC are the largest in the altitude range of 84–92 km, while the meteor counts detected from 09 UTC to 15 UTC are the lowest at other altitudes. Second, the more meteors detected by the two radars, the smaller the wind field differences retrieved by the two radars, and the closer the wind fields are to the real average wind field. Third, because the performance of the two radars is basically identical, except that the meteor counts detected by the two radars are different due to their different operating frequencies, the meteor count is the main system error of the wind fields retrieved, and the errors can be determined by the correlation coefficients of the wind fields retrieved by the two radars. Finally, in the altitude range of 76–100 km, the mean wind field differences of the two radars are less than 5 m/s. Full article
(This article belongs to the Special Issue Structure and Dynamics of Mesosphere and Lower Thermosphere)
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