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 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 Frequency spectra of horizontal winds in the mesosphere and lower thermosphere region from multistatic specular meteor radar observations during the SIMONe 2018 campaign

2021 ◽  
Author(s):  
Harikrishnan Charuvil Asokan ◽  
Jorge L Chau ◽  
Raffaele Marino ◽  
Juha Vierinen ◽  
Fabio Vargas ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Spread Spectrum ◽  
Lower Thermosphere ◽  
Geographic Area ◽  
Horizontal Wind ◽  
Small Scale ◽  
Meteor Radar ◽  
Frequency Spectra ◽  
Mesosphere And Lower Thermosphere ◽  
Field Correlation

Abstract In recent years, multistatic specular meteor radars (SMRs) have been introduced to study the Mesosphere and Lower Thermosphere (MLT) dynamics with increasing spatial and temporal resolution. In this paper, frequency spectra of MLT horizontal winds are explored through observations from a campaign using the SIMONe (Spread-spectrum Interferometric Multistatic meteor radar Observing Network) approach conducted in northern Germany in 2018 (hereafter SIMONe 2018). The seven-day SIMONe 2018 comprised of fourteen multistatic SMR links and allows to build a substantial database of specular meteor trail events, collecting more than one hundred thousand detections per day within a geographic area of $\sim $ 500 km $\times$ 500 km. We have implemented two methods to obtain the frequency spectra of the horizontal wind components: (1) Mean Wind Estimation (MWE) and (2) Wind field Correlation Function Inversion (WCFI), which utilizes the mean and the covariances of the line of sight velocities, respectively. Monte Carlo simulations of a gravity wave spectral model were implemented to validate and compare both methods. The simulation analyses suggest that the WCFI helps to capture the energy of smaller-scale wind fluctuations than those capture with MWE. Characterization of the spectral slope of the horizontal wind at different MLT altitudes has been conducted on the SIMONe 2018, and it provides evidence that gravity waves with periods smaller than seven hours and greater than two hours dominate with horizontal structures significantly larger than 500 km. These waves might be associated with secondary gravity waves during this observational campaign. In the future, these analyses can be extended to understand the significance of small-scale fluctuations in the MLT, which were not possible with conventional MWE methods.

scholarly journals The 16-day wave in the Arctic and Antarctic mesosphere and lower thermosphere

2009 ◽  
Vol 9 (6) ◽  
pp. 25213-25243
Author(s):  
K. A. Day ◽  
N. J. Mitchell
Keyword(s):  
Lower Thermosphere ◽  
Wave Activity ◽  
The Arctic ◽  
Horizontal Wind ◽  
Polar Regions ◽  
Period Range ◽  
Height Range ◽  
Entire Height ◽  
Mesosphere And Lower Thermosphere ◽  
High Degree

Abstract. The 16-day planetary wave in the polar mesosphere and lower thermosphere has been investigated using meteor radars at Esrange (68° N, 21° E) in the Arctic and Rothera (68° S, 68° W) in the Antarctic. The measurements span the 10-year interval from October 1999 to July 2009 and the 5-year interval February 2005 to July 2009, respectively. The height range covered is about 80–100 km. The wave is seen to occur in intermittent bursts, where wave amplitudes typically reach a maximum of about 10 m s−1, and never more than about 20 m s−1. Horizontal wind variance within a wave-period range of 12 to 20 days is used as a proxy for the activity of the 16-day wave. Wave activity is strong for 3 to 4 months in winter, where it is present across the entire height range observed and monthly wave variance reaches about 65 m2 s−2. Some weak and intermittent activity is observed throughout the other seasons including summer. However, there is a high degree of inter-annual variability and in some individual years wave activity is almost absent. The data are used to construct a representative climatology for the Arctic and Antarctic. The seasonal cycle of the 16-day wave is found to be very similar in both polar regions. The 16-day wave has slightly greater amplitudes in the zonal component of the winds than in the meridional. Mesospheric temperatures measured by the radars were used to further investigate the 16-day wave. The temperatures reveal a clear signature of the 16-day wave. Temperature amplitudes are generally only a few Kelvin but occasional bursts of up to 10 K have been observed. Observations of the wave in summer are sometimes consistent with the suggestion of ducting from the winter hemisphere.

scholarly journals The 16-day wave in the Arctic and Antarctic mesosphere and lower thermosphere

2010 ◽  
Vol 10 (3) ◽  
pp. 1461-1472 ◽  
Author(s):  
K. A. Day ◽  
N. J. Mitchell
Keyword(s):  
Lower Thermosphere ◽  
Wave Activity ◽  
The Arctic ◽  
Horizontal Wind ◽  
Polar Regions ◽  
Period Range ◽  
Height Range ◽  
Entire Height ◽  
Mesosphere And Lower Thermosphere ◽  
High Degree

Abstract. The 16-day planetary wave in the polar mesosphere and lower thermosphere has been investigated using meteor radars at Esrange (68° N, 21° E) in the Arctic and Rothera (68° S, 68° W) in the Antarctic. The measurements span the 10-year interval from October 1999 to July 2009 and the 5-year interval February 2005 to July 2009, respectively. The height range covered is about 80–100 km. In both polar regions the wave is seen to occur in intermittent bursts, where wave amplitudes typically reach a maximum of about 15 m s−1, and never more than about 20 m s−1. Horizontal wind variance within a wave-period range of 12 to 20 days is used as a proxy for the activity of the 16-day wave. Wave activity is strong for 3 to 4 months in winter, where it is present across the entire height range observed and monthly wave variance reaches about 65 m2 s−2. Some weak and intermittent activity is observed throughout the other seasons including summer. However, there is a high degree of inter-annual variability and in some individual years wave activity is almost absent. The data are used to construct a representative climatology for the Arctic and Antarctic. The seasonal cycle of the 16-day wave is found to be very similar in both polar regions. The 16-day wave has slightly greater amplitudes in the zonal component of the winds than in the meridional. Mesospheric temperatures measured by the radars were used to further investigate the 16-day wave. The temperatures reveal a clear signature of the 16-day wave. Temperature amplitudes are generally only a few Kelvin but occasional bursts of up to 10 K have been observed. Observations of the wave in summer are sometimes consistent with the suggestion of ducting from the winter hemisphere.

scholarly journals The two-day wave in the Antarctic and Arctic mesosphere and lower thermosphere

2009 ◽  
Vol 9 (2) ◽  
pp. 10271-10301 ◽  
Author(s):  
V. M. Tunbridge ◽  
N. J. Mitchell
Keyword(s):  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Zonal Flow ◽  
Radar Data ◽  
The Arctic ◽  
Horizontal Wind ◽  
Height Range ◽  
Zonal Winds ◽  
The Antarctic ◽  
Full Height

Abstract. There have been comparatively few studies reported of the 2-day planetary wave in the middle atmosphere at polar latitudes. Here we report studies made using high-latitude meteor radars at Rothera in the Antarctic (68° S, 68° W) and Esrange in Arctic Sweden (68° N, 21° E). Observations from 2005–2008 are used for Rothera and from 1999–2008 for Esrange. Data were recorded for heights of 80–100 km. The radar data reveal distinct summertime and wintertime 2-day waves. The Antarctic summertime wave occurs with significant amplitudes in January–February at heights between about 88–100 km. Horizontal wind monthly variances associated with the wave exceed 160 m2 s−2 and the zonal component has larger amplitudes than the meridional. In contrast, the Arctic summertime wave occurs for a longer duration, June–August and has meridional amplitudes larger than zonal. The Arctic summertime wave is weaker than that in the Antarctic and maximum monthly variances are typically 60 m2 s−2. In both hemispheres the summertime wave reaches largest amplitudes in the strongly sheared eastward zonal flow above the zero wind line and is largely absent in the westward flow below. The observed differences in the summertime wave is probably due to the differences in the background zonal winds in the two hemispheres. The Antarctic and Arctic wintertime waves have very similar behavior. The Antarctic wave has significant amplitudes in May–August and the Arctic wave in November–February. Both are evident across the full height range observed.

scholarly journals The two-day wave in the Antarctic and Arctic mesosphere and lower thermosphere

2009 ◽  
Vol 9 (17) ◽  
pp. 6377-6388 ◽  
Author(s):  
V. M. Tunbridge ◽  
N. J. Mitchell
Keyword(s):  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Zonal Flow ◽  
Radar Data ◽  
The Arctic ◽  
Horizontal Wind ◽  
Height Range ◽  
Zonal Winds ◽  
The Antarctic ◽  
Full Height

Abstract. There have been comparatively few studies reported of the 2-day planetary wave in the middle atmosphere at polar latitudes. Here we report on a study made using high-latitude meteor radars at Rothera in the Antarctic (68° S, 68° W) and Esrange in Arctic Sweden (68° N, 21° E). Observations from 2005–2008 are used for Rothera and from 1999–2008 for Esrange. Measurements were made of horizontal winds at heights of 80–100 km. The radar data revealed distinct summertime and wintertime 2-day waves. The Antarctic summertime wave occurs with significant amplitudes in January – February at heights between about 88–100 km. Horizontal wind monthly variances associated with the wave exceed 160 m2 s−2 and the zonal component has larger amplitudes than the meridional. In contrast, the Arctic summertime wave occurs for a longer duration, June–August and has meridional amplitudes larger than the zonal amplitudes. The Arctic summertime wave is weaker than that in the Antarctic and maximum monthly variances are typically 60 m2 s−2. In both hemispheres the summertime wave reaches largest amplitudes in the strongly sheared eastward zonal flow above the zero-wind line and is largely absent in the westward flow below. The observed differences in the summertime wave are probably due to the differences in the background zonal winds in the two hemispheres. The Antarctic and Arctic wintertime 2-day waves have very similar behaviour. The Antarctic wave has significant amplitudes in May–August and the Arctic wave in November–February. Both are evident across the full height range observed.

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