scholarly journals Stratospheric influence on MLT over mid-latitudes in winter by Fabry-Perot interferometer data

2020 ◽  
Author(s):  
Olga S. Zorkaltseva ◽  
Roman V. Vasilyev
Keyword(s):  
Zonal Wind ◽  
Lower Thermosphere ◽  
Optical Emission ◽  
Temporal Variations ◽  
Eastern Siberia ◽  
Wind Dispersion ◽  
Fabry Perot ◽  
Mesosphere And Lower Thermosphere ◽  
Academy Of Sciences ◽  
Parameters Measurement

Abstract. In this paper, we study the response of the mesosphere and lower thermosphere (MLT) to sudden stratospheric warmings (SSWs) and the activity of stationary planetary waves (SPWs). We observe the 557.7-nm optical emission for retrieve the MLT wind, temperature with the Fabry-Perot interferometer (FPI) that has no analogues in Russia. The FPI is located at the mid-latitudes of Eastern Siberia within the Tory Observatory (TOR) at the Institute of Solar-Terrestrial Physics of the Siberian Branch of the Russian Academy of Sciences (ISTP SB RAS, 51.8N, 103.1E). Regular interferometer monitoring started in Dec 2016. Here, we address the temporal variations in the 557.7-nm emission intensity, as well as the variations in wind, temperature, and their variability obtained by using the line parameters measurement during the 2016–2020 winters. Both SSWs and SPWs appear to have equally strong effects in the upper atmosphere. When the 557.7-nm emission decreases due to some influences from below (SSWs or SPWs), the temperature variation observed by using this line and the temperature itself increase significantly. The zonal wind dispersion does not show significant SPW- and SSW-correlated variations, but the dominant zonal wind reverses during major SSW events the same as the averaged zonal wind at 60N in the stratosphere does without significant delays.

scholarly journals Stratospheric influence on the mesosphere–lower thermosphere over mid latitudes in winter observed by a Fabry–Perot interferometer

2021 ◽  
Vol 39 (1) ◽  
pp. 267-276
Author(s):  
Olga S. Zorkaltseva ◽  
Roman V. Vasilyev
Keyword(s):  
Zonal Wind ◽  
Emission Intensity ◽  
Lower Thermosphere ◽  
Optical Emission ◽  
Temporal Variations ◽  
Upper Atmosphere ◽  
Eastern Siberia ◽  
Siberian Branch ◽  
Fabry Perot ◽  
Academy Of Sciences

Abstract. In this paper, we study the response of the mesosphere–lower thermosphere (MLT) to sudden stratospheric warmings (SSWs) and the activity of planetary waves (PWs). We observe the 557.7 nm optical emission to retrieve the MLT wind and temperature with the only Fabry–Perot interferometer (FPI) in Russia. The FPI is located at the mid latitudes of eastern Siberia within the Tory Observatory (TOR) at the Institute of Solar-Terrestrial Physics of the Siberian Branch of the Russian Academy of Sciences (ISTP SB RAS, 51.8∘ N, 103.1∘ E). Regular interferometer monitoring started in December 2016. Here, we address the temporal variations in the 557.7 nm emission intensity as well as the variations in wind and temperature measured during the 2016–2020 winters. Both SSWs and PWs appear to have equally strong effects in the upper atmosphere. When the 557.7 nm emission decreases due to some influences from below (SSWs or PWs), the temperature increases significantly, as does its variability. The dispersion of zonal wind does not show significant PW- and SSW-correlated variations, but the dominant MLT zonal wind reverses during major SSW events simultaneously with the averaged zonal wind at 60∘ N in the stratosphere.

scholarly journals Mean winds, temperatures and the 16- and 5-day planetary waves in the mesosphere and lower thermosphere over Bear Lake Observatory (42° N, 111° W)

2012 ◽  
Vol 12 (3) ◽  
pp. 1571-1585 ◽  
Author(s):  
K. A. Day ◽  
M. J. Taylor ◽  
N. J. Mitchell
Keyword(s):  
Zonal Wind ◽  
Lower Thermosphere ◽  
Planetary Waves ◽  
Zonal Winds ◽  
Annual Variability ◽  
Bear Lake ◽  
Meridional Winds ◽  
The Mean ◽  
Mesosphere And Lower Thermosphere ◽  
Wind Shears

Abstract. Atmospheric temperatures and winds in the mesosphere and lower thermosphere have been measured simultaneously using the Aura satellite and a meteor radar at Bear Lake Observatory (42° N, 111° W), respectively. The data presented in this study is from the interval March 2008 to July 2011. The mean winds observed in the summer-time over Bear Lake Observatory show the meridional winds to be equatorward at meteor heights during April−August and to reach monthly-mean velocities of −12 m s−1. The mean winds are closely related to temperatures in this region of the atmosphere and in the summer the coldest mesospheric temperatures occur about the same time as the strongest equatorward meridional winds. The zonal winds are eastward through most of the year and in the summer strong eastward zonal wind shears of up to ~4.5 m s−1 km−1 are present. However, westward winds are observed at the upper heights in winter and sometimes during the equinoxes. Considerable inter-annual variability is observed in the mean winds and temperatures. Comparisons of the observed winds with URAP and HWM-07 reveal some large differences. Our radar zonal wind observations are generally more eastward than predicted by the URAP model zonal winds. Considering the radar meridional winds, in comparison to HWM-07 our observations reveal equatorward flow at all meteor heights in the summer whereas HWM-07 suggests that only weakly equatorward, or even poleward flows occur at the lower heights. However, the zonal winds observed by the radar and modelled by HWM-07 are generally similar in structure and strength. Signatures of the 16- and 5-day planetary waves are clearly evident in both the radar-wind data and Aura-temperature data. Short-lived wave events can reach large amplitudes of up to ~15 m s−1 and 8 K and 20 m s−1 and 10 K for the 16- and 5-day waves, respectively. A clear seasonal and short-term variability are observed in the 16- and 5-day planetary wave amplitudes. The 16-day wave reaches largest amplitude in winter and is also present in summer, but with smaller amplitudes. The 5-day wave reaches largest amplitude in winter and in late summer. An inter-annual variability in the amplitude of the planetary waves is evident in the four years of observations. Some 41 episodes of large-amplitude wave occurrence are identified. Temperature and wind amplitudes for these episodes, AT and AW, that passed the Student T-test were found to be related by, AT = 0.34 AW and AT = 0.62 AW for the 16- and 5-day wave, respectively.

scholarly journals Comparison of Global Datasets of Sodium Densities in the Mesosphere and Lower Thermosphere from GOMOS, SCIAMACHY and OSIRIS Measurements and WACCM Model Simulations from 2008 to 2012

2017 ◽  
Author(s):  
Martin P. Langowski ◽  
Christian von Savigny ◽  
John P. Burrows ◽  
Didier Fussen ◽  
Erin C. M. Dawkins ◽  
...  
Keyword(s):  
Seasonal Cycle ◽  
Lower Thermosphere ◽  
Temporal Variations ◽  
Equatorial Region ◽  
Local Times ◽  
Vertical Column ◽  
Model Simulations ◽  
Mesosphere And Lower Thermosphere ◽  
Summer Minimum ◽  
Global Datasets

Abstract. During the last decade, multiple limb sounding satellites have measured the global sodium (Na) number densities in the mesosphere and lower thermosphere (MLT).Datasets are now available from GOMOS, SCIAMACHY (both on Envisat) and OSIRIS/Odin. Furthermore, global model simulations of the Na layer in the MLT simulated with WACCM-Na are available. In this paper, we compare these global datasets. Globally, there is an agreement in the observed and simulated monthly average of Na vertical column densities that were compared with each other. They show a clear seasonal cycle with a summer minimum most pronounced at the poles. They also show signs of a semi-annual oscillation in the equatorial region. The vertical column densities vary between 0.5 × 109 cm−2 to 7 × 109 cm−2 near the poles and between 3 × 109 cm−2 to 4 × 109 cm−2 at the equator. The phase of the seasonal cycle and semi-annual oscillation shows small differences between the different instruments. The full width at half maximum of the profiles is 10 to 16 km for most latitudes, but significantly smaller in the polar summer. The centroid altitudes of the measured sodium profiles range from 89 to 95 km, while the model shows on average 2 to 4 km lower centroid altitudes. This coincides with a 3 km lower mesopause altitude in the WACCM simulations compared to measurements, which may be the reason for the low centroid altitudes. Despite this global 2 to 4 km shift, the model captures latitudinal and temporal variations. The variation of the WACCM dataset during the year at different latitudes is similar to the one of the measurements. Furthermore, the differences between the measured profiles with different instruments and therefore different local times are also present in the model simulated profiles. This capturing of latitutinal and temporal variations is also found for the vertical column densities and profile widths.

scholarly journals Comparative statistical analysis of neutral wind in mid-latitude mesosphere / lower thermosphere based on meteor radar and Fabry — Perot interferome-ter data

2018 ◽  
Vol 4 (2) ◽  
pp. 49-57 ◽  
Author(s):  
Роман Васильев ◽  
Roman Vasilyev ◽  
Максим Артамонов ◽  
Maksim Artamonov ◽  
Евгений Мерзляков ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Geomagnetic Storms ◽  
Lower Thermosphere ◽  
Horizontal Wind ◽  
Neutral Wind ◽  
Eastern Siberia ◽  
Meteor Radar ◽  
Spring Period ◽  
Fabry Perot ◽  
Comparative Statistical Analysis

Studies of the upper atmosphere wind are very important both for understanding the mechanism of transformation of exposure energy into heating, movement and chemical activity of the atmosphere, and similar processes of energy transfer from lower to upper atmospheric layers. Instruments and methods for studying the wind velocity and its variations at different height levels usually complement each other in such studies. We perform a comparative analysis of information about the neutral horizontal wind over Eastern Siberia in the winter-spring period obtained by different methods. We observe some features appearing at different heights during geomagnetic storms and sudden stratospheric warming events. We propose a method for comparative statistical analysis of the neutral wind registered at different sites and show its validity. Using this method, we make a quantitative comparison of winds measured over Eastern Siberia in the winter-spring period. The wind measured by the meteor radar and Fabry-Perot interferometer at 90 km has similar direction and absolute velocity. The wind measured by the Fabry—Perot interferometer at 100 km differs from that estimated by the meteor radar only in direction. The wind measured by the Fabry—Perot interferometer at 250 km has a velocity 2.5 times faster and a direction differing by 30–40° from the wind obtained by the meteor radar.

scholarly journals Connection between the length of day and wind measurements in the mesosphere and lower thermosphere at mid- and high latitudes

2019 ◽  
Vol 37 (1) ◽  
pp. 1-14
Author(s):  
Sven Wilhelm ◽  
Gunter Stober ◽  
Vivien Matthias ◽  
Christoph Jacobi ◽  
Damian J. Murphy
Keyword(s):  
Solar Radiation ◽  
Zonal Wind ◽  
Large Scale ◽  
Lower Thermosphere ◽  
Earth’S Rotation ◽  
The Sun ◽  
Earth's Rotation ◽  
The Earth ◽  
The Mean ◽  
Mesosphere And Lower Thermosphere

Abstract. This work presents a connection between the density variation within the mesosphere and lower thermosphere (MLT) and changes in the intensity of solar radiation. On a seasonal timescale, these changes take place due to the revolution of the Earth around the Sun. While the Earth, during the northern-hemispheric (NH) winter, is closer to the Sun, the upper mesosphere expands due to an increased radiation intensity, which results in changes in density at these heights. These density variations, i.e., a vertical redistribution of atmospheric mass, have an effect on the rotation rate of Earth's upper atmosphere owing to angular momentum conservation. In order to test this effect, we applied a theoretical model, which shows a decrease in the atmospheric rotation speed of about ∼4 m s−1 at a latitude of 45∘ in the case of a density change of 1 % between 70 and 100 km. To support this statement, we compare the wind variability obtained from meteor radar (MR) and Microwave Limb Sounder (MLS) satellite observations with fluctuations in the length of a day (LOD). Changes in the LOD on timescales of a year and less are primarily driven by tropospheric large-scale geophysical processes and their impact on the Earth's rotation. A global increase in lower-atmospheric eastward-directed winds leads, due to friction with the Earth's surface, to an acceleration of the Earth's rotation by up to a few milliseconds per rotation. The LOD shows an increase during northern winter and decreases during summer, which corresponds to changes in the MLT density due to the Earth–Sun movement. Within the MLT the mean zonal wind shows similar fluctuations to the LOD on annual scales as well as longer time series, which are connected to the seasonal wind regime as well as to density changes excited by variations in the solar radiation. A direct correlation between the local measured winds and the LOD on shorter timescales cannot clearly be identified, due to stronger influences of other natural oscillations on the wind. Further, we show that, even after removing the seasonal and 11-year solar cycle variations, the mean zonal wind and the LOD are connected by analyzing long-term tendencies for the years 2005–2016.

scholarly journals Comparison of global datasets of sodium densities in the mesosphere and lower thermosphere from GOMOS, SCIAMACHY and OSIRIS measurements and WACCM model simulations from 2008 to 2012

2017 ◽  
Vol 10 (8) ◽  
pp. 2989-3006 ◽  
Author(s):  
Martin P. Langowski ◽  
Christian von Savigny ◽  
John P. Burrows ◽  
Didier Fussen ◽  
Erin C. M. Dawkins ◽  
...  
Keyword(s):  
Seasonal Cycle ◽  
Climate Model ◽  
Lower Thermosphere ◽  
Temporal Variations ◽  
Equatorial Region ◽  
Local Times ◽  
Vertical Column ◽  
Model Simulations ◽  
Mesosphere And Lower Thermosphere ◽  
Scanning Imaging

Abstract. During the last decade, several limb sounding satellites have measured the global sodium (Na) number densities in the mesosphere and lower thermosphere (MLT). Datasets are now available from Global Ozone Monitoring by Occultation of Stars (GOMOS), the SCanning Imaging Absorption spectroMeter for Atmospheric CHartography (SCIAMACHY) (both on Envisat) and the Optical Spectrograph and InfraRed Imager System (OSIRIS) (on Odin). Furthermore, global model simulations of the Na layer in the MLT simulated by the Whole Atmosphere Community Climate Model, including the Na species (WACCM-Na), are available. In this paper, we compare these global datasets.The observed and simulated monthly averages of Na vertical column densities agree reasonably well with each other. They show a clear seasonal cycle with a summer minimum most pronounced at the poles. They also show signs of a semi-annual oscillation in the equatorial region. The vertical column densities vary from 0. 5  ×  109 to 7  ×  109 cm−2 near the poles and from 3  ×  109 to 4  ×  109 cm−2 at the Equator. The phase of the seasonal cycle and semi-annual oscillation shows small differences between the Na amounts retrieved from different instruments. The full width at half maximum of the profiles is 10 to 16 km for most latitudes, but significantly smaller in the polar summer. The centroid altitudes of the measured sodium profiles range from 89 to 95 km, whereas the model shows on average 2 to 4 km lower centroid altitudes. This may be explained by the mesopause being 3 km lower in the WACCM simulations than in measurements. Despite this global 2–4 km shift, the model captures well the latitudinal and temporal variations. The variation of the WACCM dataset during the year at different latitudes is similar to the one of the measurements. Furthermore, the differences between the measured profiles with different instruments and therefore different local times (LTs) are also present in the model-simulated profiles. This capturing of latitudinal and temporal variations is also found for the vertical column densities and profile widths.

scholarly journals A quasi-27-day oscillation activity from the troposphere to the mesosphere and lower thermosphere at low latitudes

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Hao Cheng ◽  
Kaiming Huang ◽  
Alan Z. Liu ◽  
Shaodong Zhang ◽  
Chunming Huang ◽  
...  
Keyword(s):  
Zonal Wind ◽  
Layer Structure ◽  
Solar Rotation ◽  
Lower Thermosphere ◽  
Intraseasonal Oscillation ◽  
Longwave Radiation ◽  
Reanalysis Data ◽  
Lower Atmosphere ◽  
Specific Humidity ◽  
Mesosphere And Lower Thermosphere

AbstractUsing meteor radar, radiosonde observations and MERRA-2 reanalysis data from 12 August to 31 October 2006, we report a dynamical coupling from the tropical lower atmosphere to the mesosphere and lower thermosphere through a quasi-27-day intraseasonal oscillation (ISO). It is interesting that the quasi-27-day ISO is observed in the troposphere, stratopause and mesopause regions, exhibiting a three-layer structure. In the MLT, the amplitude in the zonal wind increases from about 4 ms−1 at 90 km to 15 ms−1 at 100 km, which is different from previous observations that ISOs occurs generally in winter with an amplitude peak at about 80–90 km, and then are rapidly weakened with increasing height. Outgoing longwave radiation (OLR) and specific humidity demonstrate that there is a quasi-27-day periodicity in convective activity in the tropics, which causes the ISO of the zonal wind and gravity wave (GW) activity in the troposphere. The upward propagating GWs are further modulated by the oscillation in the troposphere and upper stratosphere. As the GWs propagate to the MLT, the quasi-27-day oscillation in the wind field is induced with a clear phase opposite to that in the lower atmosphere through instability and dissipation of these modulated GWs. Wavelet analysis shows that the quasi-27-day variability in the MLT appears as a case event rather than a persistent phenomenon, and has not a clear corresponding relation with the solar rotation effect within 1 year of observations.

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