scholarly journals Retrieval of sodium number density profiles in the mesosphere and lower thermosphere from SCIAMACHY limb emission measurements

2016 ◽  
Vol 9 (1) ◽  
pp. 295-311 ◽  
Author(s):  
M. P. Langowski ◽  
C. von Savigny ◽  
J. P. Burrows ◽  
V. V. Rozanov ◽  
T. Dunker ◽  
...  
Keyword(s):  
Seasonal Variations ◽  
Lower Thermosphere ◽  
High Latitudes ◽  
Full Width ◽  
Half Maximum ◽  
Number Density ◽  
Data Set ◽  
Density Profiles ◽  
Atom Concentration ◽  
Mesosphere And Lower Thermosphere

Abstract. An algorithm has been developed for the retrieval of sodium atom (Na) number density on a latitude and altitude grid from SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) limb measurements of the Na resonance fluorescence. The results are obtained between 50 and 150 km altitude and the resulting global seasonal variations of Na are analyzed. The retrieval approach is adapted from that used for the retrieval of magnesium atom (Mg) and magnesium ion (Mg+) number density profiles recently reported by Langowski et al. (2014). Monthly mean values of Na are presented as a function of altitude and latitude. This data set was retrieved from the 4 years of spectroscopic limb data of the SCIAMACHY mesosphere and lower thermosphere (MLT) measurement mode (mid-2008 to early 2012). The Na layer has a nearly constant peak altitude of 90–93 km for all latitudes and seasons, and has a full width at half maximum of 5–15 km. Small but significant seasonal variations in Na are identified for latitudes less than 40°, where the maximum Na number densities are 3000–4000 atoms cm−3. At middle to high latitudes a clear seasonal variation with a winter maximum of up to 6000 atoms cm−3 is observed. The high latitudes, which are only measured in the summer hemisphere, have lower number densities, with peak densities being approximately 1000 Na atoms cm−3. The full width at half maximum of the peak varies strongly at high latitudes and is 5 km near the polar summer mesopause, while it exceeds 10 km at lower latitudes. In summer the Na atom concentration at high latitudes and at altitudes below 88 km is significantly smaller than that at middle latitudes. The results are compared with other observations and models and there is overall a good agreement with these.

scholarly journals Retrieval of sodium number density profiles in the mesosphere and lower thermosphere from SCIAMACHY limb emission measurements

2015 ◽  
Vol 8 (7) ◽  
pp. 7909-7952
Author(s):  
M. P. Langowski ◽  
C. von Savigny ◽  
J. P. Burrows ◽  
V. V. Rozanov ◽  
T. Dunker ◽  
...  
Keyword(s):  
Seasonal Variations ◽  
Lower Thermosphere ◽  
High Latitudes ◽  
Full Width ◽  
Half Maximum ◽  
Number Density ◽  
Data Set ◽  
Density Profiles ◽  
Atom Concentration ◽  
Mesosphere And Lower Thermosphere

Abstract. An algorithm has been developed for the retrieval of sodium atom (Na) number density on a latitude and altitude grid from SCIAMACHY limb measurements of the Na resonance fluorescence. The results are obtained between 50 and 150 km altitude and the resulting global seasonal variations of Na are analysed. The retrieval approach is adapted from that used for the retrieval of magnesium atom (Mg) and magnesium ion (Mg+) number density profiles recently reported by Langowski et al. (2014). Monthly mean values of Na are presented as a function of altitude and latitude. This data set was retrieved from the 4 years of spectroscopic limb data of the SCIAMACHY mesosphere and lower thermosphere (MLT) measurement mode. The Na layer has a nearly constant altitude of 90–93 km for all latitudes and seasons, and has a full width at half maximum of 5–15 km. Small but substantial seasonal variations in Na are identified for latitudes less than 40°, where the maximum Na number densities are 3000–4000 atoms cm−3. At mid to high latitudes a clear seasonal variation with a winter maximum of up to 6000 atoms cm−3 is observed. The high latitudes, which are only measured in the Summer Hemisphere, have lower number densities with peak densities being approximately 1000 Na atoms cm−3. The full width at half maximum of the peak varies strongly at high latitudes and is 5 km near the polar summer mesopause, while it exceeds 10 km at lower latitudes. In summer the Na atom concentration at high latitudes and at altitudes below 88 km is significantly smaller than that at mid latitudes. The results are compared with other observations and models and there is overall a good agreement with these.

scholarly journals A comparison of 11-year mesospheric and lower thermospheric winds determined by meteor and MF radar at 69 ° N

2017 ◽  
Vol 35 (4) ◽  
pp. 893-906 ◽  
Author(s):  
Sven Wilhelm ◽  
Gunter Stober ◽  
Jorge L. Chau
Keyword(s):  
Lower Thermosphere ◽  
Meridional Wind ◽  
Correction Factors ◽  
Data Set ◽  
Wind Measurements ◽  
Mesosphere And Lower Thermosphere ◽  
Thermospheric Winds ◽  
Good Agreement ◽  
Mlt Region ◽  
Mf Radar

Abstract. The Andenes Meteor Radar (MR) and the Saura Medium Frequency (MF) Radar are located in northern Norway (69° N, 16° E) and operate continuously to provide wind measurements of the mesosphere and lower thermosphere (MLT) region. We compare the two systems to find potential biases between the radars and combine the data from both systems to enhance altitudinal coverage between 60 and 110 km. The systems have altitudinal overlap between 78 and 100 km at which we compare winds and tides on the basis of hourly winds with 2 km altitude bins. Our results indicate reasonable agreement for the zonal and meridional wind components between 78 and 92 km. An exception to this is the altitude range below 84 km during the summer, at which the correlation decreases. We also compare semidiurnal and diurnal tides according to their amplitudes and phases with good agreement below 90 km for the diurnal and below 96 km for the semidiurnal tides. Based on these findings we have taken the MR data as a reference. By comparing the MF and MR winds within the overlapping region, we have empirically estimated correction factors to be applied to the MF winds. Existing gaps in that data set will be filled with weighted MF data. This weighting is done due to underestimated wind values of the MF compared to the MR, and the resulting correction factors fit to a polynomial function of second degree within the overlapping area. We are therefore able to construct a consistent and homogenous wind from approximately 60 to 110 km.

scholarly journals The 8-h tide in the mesosphere and lower thermosphere over Maui (20.75° N, 156.43° W)

2009 ◽  
Vol 27 (5) ◽  
pp. 1989-1999 ◽  
Author(s):  
G. Jiang ◽  
J. Xu ◽  
S. J. Franke
Keyword(s):  
Lower Thermosphere ◽  
Time Interval ◽  
Data Set ◽  
Height Range ◽  
Meridional Component ◽  
Zonal Component ◽  
Spring Equinox ◽  
Semiannual Variation ◽  
Mesosphere And Lower Thermosphere ◽  
Seasonal Characteristic

Abstract. Wind data collected by the Maui meteor radar (20.75° N, 156.43° W) are used to study the 8-h tide in the mesosphere and lower thermosphere (MLT) region at a low-latitude station. The data set spans the time interval from 19 May 2002 to 24 May 2007. Our results show that the 8-h tide is a regular and distinct feature over Maui. The meridional component of this wave is significantly larger than the zonal component. The meridional component exhibits a semiannual variation in amplitude, with peaks near the equinoxes, whereas the variation of the zonal component does not show this seasonal characteristic. The strongest wave motions mostly occur in the height range of 92–96 km near spring equinox (March) and at higher altitudes near autumn equinox (October). The vertical variations of 8-h tidal phase at Maui indicate an upward wave energy flux. The vertical wavelengths are ≥54 km in equinox months.

scholarly journals Seasonal Variations of High-Frequency Gravity Wave Momentum Fluxes and Their Forcing toward Zonal Winds in the Mesosphere and Lower Thermosphere over Langfang, China (39.4° N, 116.7° E)

Atmosphere ◽  
2020 ◽  
Vol 11 (11) ◽  
pp. 1253
Author(s):  
Caixia Tian ◽  
Xiong Hu ◽  
Yurong Liu ◽  
Xuan Cheng ◽  
Zhaoai Yan ◽  
...  
Keyword(s):  
Seasonal Variations ◽  
High Frequency ◽  
Momentum Flux ◽  
Lower Thermosphere ◽  
Mean Flow ◽  
Zonal Winds ◽  
Short Period ◽  
Momentum Fluxes ◽  
The Mean ◽  
Mesosphere And Lower Thermosphere

Meteor radar data collected over Langfang, China (39.4° N, 116.7° E) were used to estimate the momentum flux of short-period (less than 2 h) gravity waves (GWs) in the mesosphere and lower thermosphere (MLT), using the Hocking (2005) analysis technique. Seasonal variations in GW momentum flux exhibited annual oscillation (AO), semiannual oscillation (SAO), and quasi-4-month oscillation. Quantitative estimations of GW forcing toward the mean zonal flow were provided using the determined GW momentum flux. The mean flow acceleration estimated from the divergence of this flux was compared with the observed acceleration of zonal winds displaying SAO and quasi-4-month oscillations. These comparisons were used to analyze the contribution of zonal momentum fluxes of SAO and quasi-4-month oscillations to zonal winds. The estimated acceleration from high-frequency GWs was in the same direction as the observed acceleration of zonal winds for quasi-4-month oscillation winds, with GWs contributing more than 69%. The estimated acceleration due to Coriolis forces to the zonal wind was studied; the findings were opposite to the estimated acceleration of high-frequency GWs for quasi-4-month oscillation winds. The significance of this study lies in estimating and quantifying the contribution of the GW momentum fluxes to zonal winds with quasi-4-month periods over mid-latitude regions for the first time.

scholarly journals An empirical model of nitric oxide in the upper mesosphere and lower thermosphere based on 12 years of Odin SMR measurements

2018 ◽  
Vol 18 (18) ◽  
pp. 13393-13410 ◽  
Author(s):  
Joonas Kiviranta ◽  
Kristell Pérot ◽  
Patrick Eriksson ◽  
Donal Murtagh
Keyword(s):  
Nitric Oxide ◽  
Empirical Model ◽  
Input Data ◽  
Lower Thermosphere ◽  
Number Density ◽  
Magnetic Latitude ◽  
Auroral Activity ◽  
K Index ◽  
Solar Declination ◽  
Mesosphere And Lower Thermosphere

Abstract. Nitric oxide (NO) is produced by solar photolysis and auroral activity in the upper mesosphere and lower thermosphere region and can, via transport processes, eventually impact the ozone layer in the stratosphere. This work uses measurements of NO taken between 2004 and 2016 by the Odin sub-millimeter radiometer (SMR) to build an empirical model that links the prevailing solar and auroral conditions with the measured number density of NO. The measurement data are averaged daily and sorted into altitude and magnetic latitude bins. For each bin, a multivariate linear fit with five inputs, the planetary K index, solar declination, and the F10.7 cm flux, as well as two newly devised indices that take the planetary K index and the solar declination as inputs in order to take NO created on previous days into account, constitutes the link between environmental conditions and measured NO. This results in a new empirical model, SANOMA, which only requires the three indices to estimate NO between 85 and 115 km and between 80∘ S and 80∘ N in magnetic latitude. Furthermore, this work compares the NO calculated with SANOMA and an older model, NOEM, with measurements of the original SMR dataset, as well as measurements from four other instruments: ACE, MIPAS, SCIAMACHY, and SOFIE. The results suggest that SANOMA can capture roughly 31 %–70 % of the variance of the measured datasets near the magnetic poles, and between 16 % and 73 % near the magnetic equator. The corresponding values for NOEM are 12 %–38 % and 7 %–40 %, indicating that SANOMA captures more of the variance of the measured datasets than NOEM. The simulated NO for these regions was on average 20 % larger for SANOMA, and 78 % larger for NOEM, than the measured NO. Two main reasons for SANOMA outperforming NOEM are identified. Firstly, the input data (Odin SMR NO) for SANOMA span over 12 years, while the input data for NOEM from the Student Nitric Oxide Experiment (SNOE) only cover 1998–2000. Additionally, some of the improvement can be accredited to the introduction of the two new indices, since they include information of auroral activity on prior days that can significantly enhance the number density of NO in the MLT during winter in the absence of sunlight. As a next step, SANOMA could be used as input in chemical models, as a priori information for the retrieval of NO from measurements, or as a tool to compare Odin SMR NO with other instruments. SANOMA and accompanying scripts are available on http://odin.rss.chalmers.se (last access: 15 September 2018).

scholarly journals Observations of lunar tides in the mesosphere and lower thermosphere at Arctic and middle latitudes

2006 ◽  
Vol 6 (12) ◽  
pp. 4117-4127 ◽  
Author(s):  
D. J. Sandford ◽  
H. G. Muller ◽  
N. J. Mitchell
Keyword(s):  
Lower Thermosphere ◽  
Set Covering ◽  
The Arctic ◽  
Lunar Tide ◽  
Data Set ◽  
Height Range ◽  
Middle Latitudes ◽  
Lunar Tides ◽  
Mesosphere And Lower Thermosphere ◽  
The Uk

Abstract. Meteor radars have been used to measure the horizontal winds in the mesosphere and lower thermosphere over Castle Eaton (52° N) in the UK and over Esrange (68° N) in Arctic Sweden. We consider a 16-year data set covering the interval 1988–2004 for the UK and a 6-year data set covering the interval 1999–2005 for the Arctic. The signature of the 12.42-h (M2) lunar tide has been identified at both locations. The lunar tide is observed to reach amplitudes as large as 11 ms−1. The Arctic radar has an interferometer and so allows investigation of the vertical structure of the lunar tide. At both locations the tide has maximum amplitudes in winter with a second autumnal maximum. The amplitude is found to increase with height over the 80–100 km height range observed. Vertical wavelengths are very variable, ranging from about 15 km in summer to more than 60 km in winter. Comparisons with the Vial and Forbes (1994) model reveals generally good agreement, except in the case of the summer vertical wavelengths which are observed to be significantly shorter than predicted.

scholarly journals MIPAS observations of longitudinal oscillations in the mesosphere and the lower thermosphere: climatology of odd-parity daily frequency modes

2016 ◽  
Vol 16 (17) ◽  
pp. 11019-11041 ◽  
Author(s):  
Maya García-Comas ◽  
Francisco González-Galindo ◽  
Bernd Funke ◽  
Angela Gardini ◽  
Aythami Jurado-Navarro ◽  
...  
Keyword(s):  
Lower Thermosphere ◽  
Lower Boundary ◽  
High Latitudes ◽  
Quasi Biennial Oscillation ◽  
Propagating Waves ◽  
Daily Frequency ◽  
Mesosphere And Lower Thermosphere ◽  
Single Instrument ◽  
First Time ◽  
Biennial Oscillation

Abstract. MIPAS global Sun-synchronous observations are almost fixed in local time. Subtraction of the descending and ascending node measurements at each longitude only includes the longitudinal oscillations with odd daily frequencies nodd from the Sun's perspective at 10:00. Contributions from the background atmosphere, daily-invariant zonal oscillations and tidal modes with even-parity daily frequencies vanish. We have determined longitudinal oscillations in MIPAS temperature with nodd and wavenumber k = 0–4 from the stratosphere to 150 km from April 2007 to March 2012. To our knowledge, this is the first time zonal oscillations in temperature have been derived pole to pole in this altitude range from a single instrument. The major findings are the detection of (1) migrating tides at northern and southern high latitudes; (2) significant k = 1 activity at extratropical and high latitudes, particularly in the Southern Hemisphere; (3) k = 3 and k = 4 eastward-propagating waves that penetrate the lower thermosphere with a significantly larger vertical wavelength than in the mesosphere; and (4) a migrating tide quasi-biennial oscillation in the stratosphere, mesosphere and lower thermosphere. MIPAS global measurements of longitudinal oscillations are useful for testing tide modeling in the mesosphere and lower thermosphere region and as a lower boundary for models extending higher up in the atmosphere.

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