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 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 Global investigation of the Mg atom and ion layers using SCIAMACHY/Envisat observations between 70 and 150 km altitude and WACCM-Mg model results

2015 ◽  
Vol 15 (1) ◽  
pp. 273-295 ◽  
Author(s):  
M. P. Langowski ◽  
C. von Savigny ◽  
J. P. Burrows ◽  
W. Feng ◽  
J. M. C. Plane ◽  
...  
Keyword(s):  
Seasonal Cycle ◽  
Column Density ◽  
Lower Thermosphere ◽  
High Latitudes ◽  
Vertical Column ◽  
Peak Density ◽  
Vertical Column Density ◽  
Summer Maximum ◽  
Constant Altitude ◽  
Summer Minimum

Abstract. Mg and Mg+ concentration fields in the upper mesosphere/lower thermosphere (UMLT) region are retrieved from SCIAMACHY/Envisat limb measurements of Mg and Mg+ dayglow emissions using a 2-D tomographic retrieval approach. The time series of monthly mean Mg and Mg+ number density and vertical column density in different latitudinal regions are presented. Data from the limb mesosphere–thermosphere mode of SCIAMACHY/Envisat are used, which cover the 50 to 150 km altitude region with a vertical sampling of ≈3.3 km and latitudes up to 82°. The high latitudes are not observed in the winter months, because there is no dayglow emission during polar night. The measurements were performed every 14 days from mid-2008 until April 2012. Mg profiles show a peak at around 90 km altitude with a density between 750 cm−3 and 1500 cm−3. Mg does not show strong seasonal variation at latitudes below 40°. For higher latitudes the density is lower and only in the Northern Hemisphere a seasonal cycle with a summer minimum is observed. The Mg+ peak occurs 5–15 km above the neutral Mg peak altitude. These ions have a significant seasonal cycle with a summer maximum in both hemispheres at mid and high latitudes. The strongest seasonal variations of Mg+ are observed at latitudes between 20 and 40° and the density at the peak altitude ranges from 500 cm−3 to 4000 cm−3. The peak altitude of the ions shows a latitudinal dependence with a maximum at mid latitudes that is up to 10 km higher than the peak altitude at the equator. The SCIAMACHY measurements are compared to other measurements and WACCM model results. The WACCM results show a significant seasonal variability for Mg with a summer minimum, which is more clearly pronounced than for SCIAMACHY, and globally a higher peak density than the SCIAMACHY results. Although the peak density of both is not in agreement, the vertical column density agrees well, because SCIAMACHY and WACCM profiles have different widths. The agreement between SCIAMACHY and WACCM results is much better for Mg+ with both showing the same seasonality and similar peak density. However, there are also minor differences, e.g. WACCM showing a nearly constant altitude of the Mg+ layer's peak density for all latitudes and seasons.

scholarly journals The roles of vertical advection and eddy diffusion in the equatorial mesospheric semi-annual oscillation (MSAO)

2013 ◽  
Vol 13 (15) ◽  
pp. 7813-7824 ◽  
Author(s):  
R. L. Gattinger ◽  
E. Kyrölä ◽  
C. D. Boone ◽  
W. F. J. Evans ◽  
K. A. Walker ◽  
...  
Keyword(s):  
Driving Forces ◽  
Eddy Diffusion ◽  
Equatorial Region ◽  
Local Times ◽  
Model Simulations ◽  
Vertical Advection ◽  
Diffusion Rates ◽  
D Model ◽  
Vertical Eddy

Abstract. Observations of the mesospheric semi-annual oscillation (MSAO) in the equatorial region have been reported dating back several decades. Seasonal variations in both species densities and airglow emissions are well documented. The extensive observations available offer an excellent case study for comparison with model simulations. A broad range of MSAO measurements is summarised with emphasis on the 80–100 km region. The objective here is not to address directly the complicated driving forces of the MSAO, but rather to employ a combination of observations and model simulations to estimate the limits of some of the underlying dynamical processes. Photochemical model simulations are included for near-equinox and near-solstice conditions, the two times with notable differences in the observed MSAO parameters. Diurnal tides are incorporated in the model to facilitate comparisons of observations made at different local times. The roles of water vapour as the "driver" species and ozone as the "response" species are examined to test for consistency between the model results and observations. The simulations suggest the interactions between vertical eddy diffusion and background vertical advection play a significant role in the MSAO phenomenon. Further, the simulations imply there are rigid limits on vertical advection rates and eddy diffusion rates. For August at the Equator, 90 km altitude, the derived eddy diffusion rate is approximately 1 × 106 cm2 s−1 and the vertical advection is upwards at 0.8 cm s−1. For April the corresponding values are 4 × 105 cm2 s−1 and 0.1 cm s−1. These results from the current 1-D model simulations will need to be verified by a full 3-D simulation. Exactly how vertical advection and eddy diffusion are related to gravity wave momentum as discussed by Dunkerton (1982) three decades ago remains to be addressed.

scholarly journals Global investigation of the Mg atom and ion layers using SCIAMACHY/Envisat observations between 70 km and 150 km altitude and WACCM-Mg model results

2014 ◽  
Vol 14 (2) ◽  
pp. 1971-2019 ◽  
Author(s):  
M. Langowski ◽  
C. von Savigny ◽  
J. P. Burrows ◽  
W. Feng ◽  
J. M. C. Plane ◽  
...  
Keyword(s):  
Lower Thermosphere ◽  
Equatorial Region ◽  
High Latitudes ◽  
Polar Night ◽  
Density Maximum ◽  
Vertical Column ◽  
Latitudinal Dependence ◽  
Vertical Column Density ◽  
Summer Maximum ◽  
Similar Peak

Abstract. Mg and Mg+ concentration fields in the upper mesosphere/lower thermosphere (UMLT) region are retrieved from SCIAMACHY/Envisat limb measurements of Mg and Mg+ dayglow emissions using a 2-D tomographic retrieval approach. The time series of monthly means of Mg and Mg+ for number density as well as vertical column density in different latitudinal regions are shown. Data from the limb mesosphere-thermosphere mode of SCIAMACHY/Envisat are used, which covers the 50 km to 150 km altitude region with a vertical sampling of 3.3 km and a highest latitude of 82°. The high latitudes are not covered in the winter months, because there is no dayglow emission during polar night. The measurements were performed every 14 days from mid-2008 until April 2012. Mg profiles show a peak at around 90 km altitude with a density between 750 cm−3 and 2000 cm−3. Mg does not show strong seasonal variation at mid-latitudes. The Mg+ peak occurs 5–15 km above the neutral Mg peak at 95–105 km. Furthermore, the ions show a significant seasonal cycle with a summer maximum in both hemispheres at mid- and high-latitudes. The strongest seasonal variations of the ions are observed at mid-latitudes between 20–40° and densities at the peak altitude range from 500 cm−3 to 6000 cm−3. The peak altitude of the ions shows a latitudinal dependence with a maximum at mid-latitudes that is up to 10 km higher than the peak altitude at the equator. The SCIAMACHY measurements are compared to other measurements and WACCM model results. In contrast to the SCIAMACHY results, the WACCM results show a strong seasonal variability for Mg with a winter maximum, which is not observable by SCIAMACHY, and globally higher peak densities. Although the peak densities do not agree the vertical column densities agree, since SCIAMACHY results show a wider vertical profile. The agreement of SCIAMACHY and WACCM results is much better for Mg+, showing the same seasonality and similar peak densities. However, there are the following minor differences: there is no latitudinal dependence of the peak altitude for WACCM and the density maximum, passing the equatorial region during equinox conditions, is not reduced as for SCIAMACHY.

scholarly journals The ultra-fast Kelvin waves in the equatorial ionosphere: observations and modeling

2013 ◽  
Vol 31 (2) ◽  
pp. 209-215 ◽  
Author(s):  
A. N. Onohara ◽  
I. S. Batista ◽  
H. Takahashi
Keyword(s):  
Lower Thermosphere ◽  
Equatorial Ionosphere ◽  
Equatorial Region ◽  
South American ◽  
Meteor Radar ◽  
Vertical Coupling ◽  
Wave Characteristics ◽  
E Region ◽  
Mesosphere And Lower Thermosphere ◽  
Mlt Region

Abstract. The main purpose of this study is to investigate the vertical coupling between the mesosphere and lower thermosphere (MLT) region and the ionosphere through ultra-fast Kelvin (UFK) waves in the equatorial atmosphere. The effect of UFK waves on the ionospheric parameters was estimated using an ionospheric model which calculates electrostatic potential in the E-region and solves coupled electrodynamics of the equatorial ionosphere in the E- and F-regions. The UFK wave was observed in the South American equatorial region during February–March 2005. The MLT wind data obtained by meteor radar at São João do Cariri (7.5° S, 37.5° W) and ionospheric F-layer bottom height (h'F) observed by ionosonde at Fortaleza (3.9° S; 38.4° W) were used in order to calculate the wave characteristics and amplitude of oscillation. The simulation results showed that the combined electrodynamical effect of tides and UFK waves in the MLT region could explain the oscillations observed in the ionospheric parameters.

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 Water vapour and the equatorial mesospheric semi-annual oscillation (MSAO)

2013 ◽  
Vol 13 (1) ◽  
pp. 729-763
Author(s):  
R. L. Gattinger ◽  
E. Kyrölä ◽  
C. D. Boone ◽  
W. F. J. Evans ◽  
K. A. Walker ◽  
...  
Keyword(s):  
Water Vapour ◽  
Significant Role ◽  
Seasonal Variations ◽  
Equatorial Region ◽  
Local Times ◽  
Mixing Rate ◽  
Model Simulations ◽  
Vertical Advection ◽  
Airglow Emissions

Abstract. Observations of the mesospheric semi-annual oscillation (MSAO) in the equatorial region have been reported dating back several decades. Seasonal variations in both species densities and airglow emissions are well documented. The extensive observations available offer an excellent case study for comparison with model simulations. The broad range of measurements is summarised with emphasis on the 80 to 100 km region. Photochemical model simulations are described for near-equinox and near-solstice conditions, the two times with notable differences in the observed MSAO parameters. Diurnal tides are included in order to facilitate comparisons of observations made at different local times. The roles of water vapour as the "driver" species and ozone as the "response" species are examined to test for consistency between the model results and observations. The model simulations suggest the interactions between eddy mixing and background vertical advection play a significant role in the MSAO phenomenon. At the equator, 90 km altitude, the derived eddy mixing rate is approximately 1 × 106 cm2 s−1 and vertical advection 0.8 cm s−1. For April the corresponding values are 4 × 105 cm2 s−1 and 0.1 cm s−1.

Dynamics of the lower thermosphere consistent with satellite observations of 5577 Å airglow: II. Atomic oxygen, local turbulence, and global circulation results

1984 ◽  
Vol 62 (4) ◽  
pp. 382-395 ◽  
Author(s):  
R. D. Elphinstone ◽  
J. S. Murphree ◽  
L. L. Cogger
Keyword(s):  
Oxygen Concentration ◽  
Atomic Oxygen ◽  
Lower Thermosphere ◽  
Eddy Diffusion ◽  
Temporal Variations ◽  
Meridional Flow ◽  
Equatorial Region ◽  
Small Scale ◽  
Global Dynamics ◽  
Atomic Oxygen Concentration

Satellite airglow observations in conjunction with a model for the photochemical and dynamical processes in the altitude range 80 to 120 km have been used to obtain the global and temporal variations of atomic oxygen concentration, eddy diffusion, and circulation. The concentration of atomic oxygen shows midlatitude peaks near equinox, and minima about one month after solstice. Average values at midlatitudes are about 1.3 times those at the equator. Small scale turbulence decreases away from the equatorial region in the postequinox period, while near solstice the turbulence is stronger and more uniform with latitude. At equinox, poleward meridional winds of 5–10 m/s are accompanied by upward winds at the equator and downward winds at midlatitudes. There is a slow transition from the dynamics occurring at equinox to those at solstice. At solstice, vertical wind velocities near 110 km of about 10–15 cm/s are upward in the summer and downward in the winter. About one month after solstice, the strength of global dynamics (both turbulence and circulation) reaches a maximum and the global atomic oxygen concentration is lowest. At this time a summer-to-winter flow occurs at high altitudes (> 110 km) accompanied by a return meridional flow below about 105 km.

scholarly journals Large-Scale Waves in the Mesosphere and Lower Thermosphere Observed by SABER

2005 ◽  
Vol 62 (12) ◽  
pp. 4384-4399 ◽  
Author(s):  
Rolando R. Garcia ◽  
Ruth Lieberman ◽  
James M. Russell ◽  
Martin G. Mlynczak
Keyword(s):  
Large Scale ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Normal Modes ◽  
Zonal Winds ◽  
Broadband Emission ◽  
Summer Hemisphere ◽  
Mean Structure ◽  
Mesosphere And Lower Thermosphere ◽  
The Tropics

Abstract Observations made by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on board NASA’s Thermosphere–Ionosphere–Mesosphere Energetics and Dynamics (TIMED) satellite have been processed using Salby’s fast Fourier synoptic mapping (FFSM) algorithm. The mapped data provide a first synoptic look at the mean structure and traveling waves of the mesosphere and lower thermosphere (MLT) since the launch of the TIMED satellite in December 2001. The results show the presence of various wave modes in the MLT, which reach largest amplitude above the mesopause and include Kelvin and Rossby–gravity waves, eastward-propagating diurnal oscillations (“non-sun-synchronous tides”), and a set of quasi-normal modes associated with the so-called 2-day wave. The latter exhibits marked seasonal variability, attaining large amplitudes during the solstices and all but disappearing at the equinoxes. SABER data also show a strong quasi-stationary Rossby wave signal throughout the middle atmosphere of the winter hemisphere; the signal extends into the Tropics and even into the summer hemisphere in the MLT, suggesting ducting by westerly background zonal winds. At certain times of the year, the 5-day Rossby normal mode and the 4-day wave associated with instability of the polar night jet are also prominent in SABER data.

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