scholarly journals Mean winds and tides in the Arctic mesosphere and lower thermosphere

2002 ◽  
Vol 107 (A1) ◽  
Author(s):  
N. J. Mitchell
Keyword(s):  
Lower Thermosphere ◽  
The Arctic ◽  
Mesosphere And Lower Thermosphere

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 Tidal oscillations of the Arctic upper mesosphere and lower thermosphere in winter

1997 ◽  
Vol 102 (A3) ◽  
pp. 4511-4520 ◽  
Author(s):  
I. Oznovich ◽  
D. J. McEwen ◽  
G. G. Sivjee ◽  
R. L. Walterscheid
Keyword(s):  
Lower Thermosphere ◽  
The Arctic ◽  
Mesosphere And Lower Thermosphere

scholarly journals Monthly mean climatology of the prevailing winds and tides in the Arctic mesosphere/lower thermosphere

2004 ◽  
Vol 22 (10) ◽  
pp. 3395-3410 ◽  
Author(s):  
Y. I. Portnyagin ◽  
T. V. Solovjova ◽  
N. A. Makarov ◽  
E. G. Merzlyakov ◽  
A. H. Manson ◽  
...  
Keyword(s):  
Vertical Structure ◽  
Lower Thermosphere ◽  
Meridional Wind ◽  
The Arctic ◽  
Different Types ◽  
Mlt Dynamics ◽  
Mesosphere And Lower Thermosphere ◽  
Resolute Bay ◽  
Mlt Region

Abstract. The Arctic MLT wind regime parameters measured at the ground-based network of MF and meteor radar stations (Andenes 69° N, Tromsø 70° N, Esrange 68° N, Dixon 73.5° N, Poker Flat 65° N and Resolute Bay 75° N) are discussed and compared with those observed in the mid-latitudes. The network of the ground-based MF and meteor radars for measuring winds in the Arctic upper mesosphere and lower thermosphere provides an excellent opportunity for study of the main global dynamical structures in this height region and their dependence from longitude. Preliminary estimates of the differences between the measured winds and tides from the different radar types, situated 125-273km apart (Tromsø, Andenes and Esrange), are provided. Despite some differences arising from using different types of radars it is possible to study the dynamical wind structures. It is revealed that most of the observed dynamical structures are persistent from year to year, thus permitting the analysis of the Arctic MLT dynamics in a climatological sense. The seasonal behaviour of the zonally averaged wind parameters is, to some extent, similar to that observed at the moderate latitudes. However, the strength of the winds (except the prevailing meridional wind and the diurnal tide amplitudes) in the Arctic MLT region is, in general, less than that detected at the moderate latitudes, decreasing toward the pole. There are also some features in the vertical structure and seasonal variations of the Arctic MLT winds which are different from the expectations of the well-known empirical wind models CIRA-86 and HWM-93. The tidal phases show a very definite longitudinal dependence that permits the determination of the corresponding zonal wave numbers. It is shown that the migrating tides play an important role in the dynamics of the Arctic MLT region. However, there are clear indications with the presence in some months of non-migrating tidal modes of significant appreciable amplitude.

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

2006 ◽  
Vol 6 (3) ◽  
pp. 4643-4672 ◽  
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.

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