scholarly journals A comparative study of winds and tidal variability in the mesosphere/lower-thermosphere region over Bulgaria and the UK

2000 ◽  
Vol 18 (10) ◽  
pp. 1304-1315 ◽  
Author(s):  
D. Pancheva ◽  
P. Mukhtarov ◽  
N. J. Mitchell ◽  
A. G. Beard ◽  
H. G. Muller
Keyword(s):  
Middle Atmosphere ◽  
Spatial Scales ◽  
Lower Thermosphere ◽  
Planetary Waves ◽  
Wave Number ◽  
Linear Interaction ◽  
Zonal Wave Number ◽  
Tidal Variability ◽  
Cross Wavelet Analysis ◽  
The Uk

Abstract. Meteor radars located in Bulgaria and the UK have been used to simultaneously measure winds in the mesosphere/lower-thermosphere region near 42.5°N, 26.6°E and 54.5°N, 3.9°W, respectively, over the period January 1991 to June 1992. The data have been used to investigate planetary waves and diurnal and semidiurnal tidal variability over the two sites. The tidal amplitudes at each site exhibit fluctuations as large as 300% on time scales from a few days to the intra-seasonal, with most of the variability being at intra-seasonal scales. Spectral and cross-wavelet analysis reveals closely related tidal variability over the two sites, indicating that the variability occurs on spatial scales large compared to the spacing between the two radars. In some, but not all, cases, periodic variability of tidal amplitudes is associated with simultaneously present planetary waves of similar period, suggesting the variability is a consequence of non-linear interaction. Calculation of the zonal wave number of a number of large amplitude planetary waves suggests that during summer 1991 the 2-day wave had a zonal wave number of 3, but that during January–February 1991 it had a zonal wave number of 4.Key words: Meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides)

scholarly journals Intercomparison of Middle Atmospheric Meteorological Analyses for the Northern Hemisphere Winter 2009–2010

2021 ◽  
Author(s):  
John P. McCormack ◽  
V. Lynn Harvey ◽  
Nicholas Pedatella ◽  
Dai Koshin ◽  
Kaoru Sato ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Planetary Waves ◽  
Wave Number ◽  
Physical Mechanisms ◽  
Wide Range ◽  
Zonal Wave Number ◽  
Analysis System ◽  
Hemisphere Winter

Abstract. Detailed meteorological analyses based on observations extending through the middle atmosphere (~15–100 km altitude) can provide key information to whole atmosphere modelling systems regarding the physical mechanisms linking day-to-day changes in ionospheric electron density to meteorological variability near the Earth’s surface. It is currently unclear how middle atmosphere analyses produced by various research groups consistently represent the wide range of proposed linking mechanisms involving migrating and non-migrating tides, planetary waves, gravity waves, and their impact on the zonal mean state in the mesosphere and lower thermosphere (MLT) region. To begin to address this issue, we present the first intercomparison among four such analyses, JAGUAR-DAS, MERRA-2, NAVGEM-HA, and WACCMX+DART, focusing on the Northern Hemisphere (NH) 2009–2010 winter that includes a major stratospheric sudden warming (SSW) in late January. This intercomparison examines the altitude, latitude, and time dependences of zonal mean zonal winds and temperatures among these four analyses over the 1 December 2009–31 March 2010 period, as well as latitude and altitude dependences of monthly mean amplitudes of the diurnal and semidiurnal migrating solar tides, the eastward propagating diurnal zonal wave number 3 nonmigrating tide, and traveling planetary waves associated with the quasi-5 day and quasi-2-day Rossby modes. Our results show generally good agreement among the four analyses up to the stratopause (~50 km altitude). Large discrepancies begin to emerge in the MLT owing to (1) differences in the types of satellite data assimilated by each system and (2) differences in the details of the global atmospheric models used by each analysis system. The results of this intercomparison provide initial estimates of uncertainty in analyses commonly used to constrain middle atmospheric meteorological variability in whole atmosphere model simulations.

scholarly journals STATISTICALLY SIGNIFICANT ESTIMATES OF INFLUENCE OF SOLAR ACTIVITY ON PLANETARY WAVES IN THE MIDDLE ATMOSPHERE OF THE NORTHERN HEMISPHERE AS DERIVED FROM MUAM MODEL DATA

2019 ◽  
Vol 5 (4) ◽  
pp. 64-72
Author(s):  
Andrey Koval
Keyword(s):  
Solar Activity ◽  
Northern Hemisphere ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Planetary Waves ◽  
Wave Number ◽  
Winter Period ◽  
Long Period ◽  
Neutral Gas ◽  
Solar Radio Flux

Numerical simulation has been used to examine the effect of changes in solar activity (SA) in the thermosphere on amplitudes of long-period planetary waves (PW) for the winter period in the Northern Hemisphere. The model of the middle and upper atmosphere (MUAM) is used. It allows simulations of general atmospheric circulation at altitudes 0–300 km. In order to reproduce SA changes, different values of the solar radio flux at a wavelength of 10.7 cm at an altitude of more than 100 km are set in the MUAM radiation block. To take into account the effect of charged particles in the ionosphere on the neutral gas dynamics, ionospheric conductivities for different SA levels are included in MUAM. To improve the statistical reliability of the results, two ensembles of model simulations consisting of 16 runs corresponding to the minimum and maximum SA have been obtained. The statistical confidence of average differences in PW amplitudes between high and low SA has been calculated. The results are shown to be reliable in almost the entire altitude range 0–300 km. Results of the simulations have shown for the first time that statistically significant differences in amplitudes of long-period PWs can reach 10–15 % in the middle atmosphere of the Northern Hemisphere, depending on the zonal wave number. At the same time, reflection of PWs at altitudes of lower thermosphere has a significant effect on the PW structure in the middle atmosphere.

scholarly journals STATISTICALLY SIGNIFICANT ESTIMATES OF INFLUENCE OF SOLAR ACTIVITY ON PLANETARY WAVES IN THE MIDDLE ATMOSPHERE OF THE NORTHERN HEMISPHERE AS DERIVED FROM MUAM MODEL DATA

2019 ◽  
Vol 5 (4) ◽  
pp. 53-59
Author(s):  
Andrey Koval
Keyword(s):  
Solar Activity ◽  
Northern Hemisphere ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Planetary Waves ◽  
Wave Number ◽  
Winter Period ◽  
Long Period ◽  
Neutral Gas ◽  
Solar Radio Flux

Numerical simulation has been used to examine the effect of changes in solar activity (SA) in the thermosphere on amplitudes of long-period planetary waves (PW) for the winter period in the Northern Hemisphere. The model of the middle and upper atmosphere (MUAM) is used. It allows simulations of general atmospheric circulation at altitudes 0–300 km. In order to reproduce SA changes, different values of the solar radio flux at a wavelength of 10.7 cm at an altitude of more than 100 km are set in the MUAM radiation block. To take into account the effect of charged particles in the ionosphere on the neutral gas dynamics, ionospheric conductivities for different SA levels are included in MUAM. To improve the statistical reliability of the results, two ensembles of model simulations consisting of 16 runs corresponding to the minimum and maximum SA have been obtained. The statistical confidence of average differences in PW amplitudes between high and low SA has been calculated. The results are shown to be reliable in almost the entire altitude range 0–300 km. Results of the simulations have shown for the first time that statistically significant differences in amplitudes of long-period PWs can reach 10–15 % in the middle atmosphere of the Northern Hemisphere, depending on the zonal wave number. At the same time, reflection of PWs at altitudes of lower thermosphere has a significant effect on the PW structure in the middle atmosphere.

scholarly journals Intradiurnal wind variations observed in the lower thermosphere over the South Pole

2000 ◽  
Vol 18 (5) ◽  
pp. 547-554 ◽  
Author(s):  
Y. I. Portnyagin ◽  
J. M. Forbes ◽  
E. G. Merzlyakov ◽  
N. A. Makarov ◽  
S. E. Palo
Keyword(s):  
Middle Atmosphere ◽  
Lamb Waves ◽  
Lower Thermosphere ◽  
Winter Season ◽  
Internal Gravity Wave ◽  
Wave Number ◽  
South Pole ◽  
Seasonal Behavior ◽  
Linear Interaction ◽  
Short Period

Abstract. The first meteor radar measurements of meridional winds in the lower thermosphere (about 95 ± 5 km), along four azimuth directions: 0°, 90°E, 180° and 90°W; approximately 2° from the geographic South Pole were made during two observational campaigns: January 19, 1995-January 26, 1996, and November 21, 1996-January 27, 1997. Herein we report analyses of the measurement results, obtained during the first campaign, which cover the whole one-year period, with particular emphasis on the transient nature and seasonal behavior of the main parameters of the intradiurnal wind oscillations. To analyze the data, two complementary methods are used: the well-known periodogram (FFT) technique and the S-transform technique. The most characteristic periods of the intradiurnal oscillations are found to be rather uniformly spread between about 7 h and 12 h. All of these oscillations are westward-propagating with zonal wave number s=1 and their usual duration is confined to several periods. During the austral winter season the oscillations with periods less than 12 h are the most intensive, while during summer season the 12-h oscillations dominate. Lamb waves and internal-gravity wave propagation, non-linear interaction of the short-period tides, excitation in situ of the short period waves may be considered as possible processes which are responsible for intradiurnal wind oscillations in the lower thermosphere over South Pole.Key words: Meteorology and atmospheric dynamics (middle atmosphere dynamics; thermospheric dynamics; waves and tides)

scholarly journals Intercomparison of middle atmospheric meteorological analyses for the Northern Hemisphere winter 2009–2010

2021 ◽  
Vol 21 (23) ◽  
pp. 17577-17605
Author(s):  
John P. McCormack ◽  
V. Lynn Harvey ◽  
Cora E. Randall ◽  
Nicholas Pedatella ◽  
Dai Koshin ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Wave Number ◽  
Physical Mechanisms ◽  
Modeling Systems ◽  
Zonal Wave Number ◽  
Analysis System ◽  
Hemisphere Winter ◽  
Wave Induced

Abstract. Detailed meteorological analyses based on observations extending through the middle atmosphere (∼ 15 to 100 km altitude) can provide key information to whole atmosphere modeling systems regarding the physical mechanisms linking day-to-day changes in ionospheric electron density to meteorological variability near the Earth's surface. However, the extent to which independent middle atmosphere analyses differ in their representation of wave-induced coupling to the ionosphere is unclear. To begin to address this issue, we present the first intercomparison among four such analyses, JAGUAR-DAS, MERRA-2, NAVGEM-HA, and WACCMX+DART, focusing on the Northern Hemisphere (NH) 2009–2010 winter, which includes a major sudden stratospheric warming (SSW). This intercomparison examines the altitude, latitude, and time dependences of zonal mean zonal winds and temperatures among these four analyses over the 1 December 2009 to 31 March 2010 period, as well as latitude and altitude dependences of monthly mean amplitudes of the diurnal and semidiurnal migrating solar tides, the eastward-propagating diurnal zonal wave number 3 nonmigrating tide, and traveling planetary waves associated with the quasi-5 d and quasi-2 d Rossby modes. Our results show generally good agreement among the four analyses up to the stratopause (∼ 50 km altitude). Large discrepancies begin to emerge in the mesosphere and lower thermosphere owing to (1) differences in the types of satellite data assimilated by each system and (2) differences in the details of the global atmospheric models used by each analysis system. The results of this intercomparison provide initial estimates of uncertainty in analyses commonly used to constrain middle atmospheric meteorological variability in whole atmosphere model simulations.

scholarly journals Forcing mechanisms of the 6 h tide in the mesosphere/lower thermosphere

2018 ◽  
Vol 16 ◽  
pp. 141-147 ◽  
Author(s):  
Christoph Jacobi ◽  
Christoph Geißler ◽  
Friederike Lilienthal ◽  
Amelie Krug
Keyword(s):  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Radar Data ◽  
Radiation Absorption ◽  
Semidiurnal Tide ◽  
Bispectral Analysis ◽  
Solar Forcing ◽  
Linear Interaction ◽  
Non Linear ◽  
Forcing Mechanisms

Abstract. Solar tides such as the diurnal and semidiurnal tide, are forced in the lower and middle atmosphere through the diurnal cycle of solar radiation absorption. This is also the case with higher harmonics like the quarterdiurnal tide (QDT), but for these also non-linear interaction of tides such as the self-interaction of the semidiurnal tide, or the interaction of terdiurnal and diurnal tides, are discussed as possible forcing mechanism. To shed more light on the sources of the QDT, 12 years of meteor radar data at Collm (51.3∘ N, 13∘ E) have been analyzed with respect to the seasonal variability of the QDT at 82–97 km altitude, and bispectral analysis has been applied. The results indicate that non-linear interaction, in particular self-interaction of the semidiurnal tide probably plays an important role in winter, but to a lesser degree in summer. Numerical modelling of 6 h amplitudes qualitatively reproduces the gross seasonal structure of the observed 6 h wave at Collm. Model experiments with removed tidal forcing mechanisms lead to the conclusion that, although non-linear tidal interaction is one source of the QDT, the major forcing mechanism is direct solar forcing of the 6 h tidal components.

Short term tidal variability in stratosphere using ERA-interim and CMAM temperature data and comparison with satellite retrievals

2021 ◽  
Author(s):  
Subhajit Debnath ◽  
Uma Das
Keyword(s):  
Middle Atmosphere ◽  
Window Size ◽  
Temperature Data ◽  
Short Term ◽  
Transform Method ◽  
Data Set ◽  
Linear Interaction ◽  
Non Linear ◽  
Tidal Variability ◽  
Short Term Variability

<p>A short term variability of migrating and non migrating tide is investigated in the stratosphere from the regular Canadian Middle Atmosphere Model (CMAM) and reanalysis ERA-interim temperature and wind dataset during winter of 2006 to 2010. Short term variability of tides is examined by ±10 day’s window size from Earth’s surface to 1hPa pressure level. To examine the short term variability of migrating and non migrating tide in stratosphere, we applied the fast fourier transform method to the CMAM30 and ERA-interim observation. The results reveal that tide changes with amplitude of 1-2K regularly on short timescales (21days) in stratosphere. Similar variability occurs in ERA-interim reanalysis observation. Non-migrating tide DS0 shows strong winter features with finer variation during 2009 and 2010 at 65°N. The short term variability of DE3 tide in stratosphere during 2008 and 2010 may be driven by zonal mean wind and non linear interaction with planetary wave. Amplitude of DW1 shows day to day variabilities clearly during winter of 2006, 2008 and 2009 at 0.7hPa over the equator and mid-latitude while the peak of DW1 is absent at 1hPa and 10hPa from CMAM temperature data set. Short term tidal variability in the stratosphere is not related to a single source. It depends on ozone density, zonal mean wind, and wave-wave non linear interactions. By using smaller window size, short term variabilities and finer variation of non migrating tides and SPW1 are understood. These results will be compared to results from satellite temperature data set, particularly FORMOSAT-3/COMSIC, for investigating short term tidal variability in the stratosphere.</p>

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

1999 ◽  
Vol 17 (11) ◽  
pp. 1447-1456 ◽  
Author(s):  
N. J. Mitchell ◽  
H. R. Middleton ◽  
A. G. Beard ◽  
P. J. S. Williams ◽  
H. G. Muller
Keyword(s):  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Late Summer ◽  
Wave Activity ◽  
Motion Field ◽  
Mesopause Region ◽  
Waves And Tides ◽  
Mesosphere And Lower Thermosphere ◽  
Thermospheric Dynamics ◽  
The Uk

Abstract. A meteor radar located at Sheffield in the UK has been used to measure wind oscillations with periods in the range 10–28 days in the mesosphere/lower-thermosphere region at 53.5°N, 3.9°W from January 1990 to August 1994. The data reveal a motion field in which wave activity occurs over a range of frequencies and in episodes generally lasting for less than two months. A seasonal cycle is apparent in which the largest observed amplitudes are as high as 14 ms–1 and are observed from January to mid-April. A minimum in activity occurs in late June to early July. A second, smaller, maximum follows in late summer/autumn where amplitudes reach up to 7–10 ms–1. Considerable interannual variability is apparent but wave activity is observed in the summers of all the years examined, albeit at very small amplitudes near mid summer. This behaviour suggests that the equatorial winds in the mesopause region do not completely prevent inter-hemispheric ducting of the wave from the winter hemisphere, or that it is generated in situ.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; thermospheric dynamics; waves and tides)

scholarly journals Zonal wave numbers 1-5 in planetary waves from the TOMS total ozone at 65° S

2005 ◽  
Vol 23 (5) ◽  
pp. 1565-1573 ◽  
Author(s):  
A. Grytsai ◽  
Z. Grytsai ◽  
A. Evtushevsky ◽  
G. Milinevsky ◽  
N. Leonov
Keyword(s):  
Total Ozone ◽  
General Circulation ◽  
Middle Atmosphere ◽  
Polar Vortex ◽  
Planetary Waves ◽  
Wave Number ◽  
Stratospheric Polar Vortex ◽  
Term Change ◽  
Wave Numbers ◽  
The Difference

Abstract. Planetary waves in the total ozone at the southern latitude of 65° S are studied to obtain the main characteristics of the zonal wave numbers 1–5. The TOMS total ozone data were used to analyze the amplitude and periodicity variations of the five spectral components during August-December of 1979–2003. A presence of the shorter period of waves 1–3 in 1996 (7 days) in comparison with 2002 (8–12 days) is revealed which can be attributed to the distinction in conditions of typical and anomalously weak stratospheric polar vortex, probably, a strong and weak mean zonal wind. The interannual variations of the monthly and 5-month mean amplitudes of the zonal wave numbers 1–5 are described. Wave 1 has the largest amplitude in October (up to 139 DU in 2000) and increasing amplitude trend (15 DU/decade for October 1979–2003). The 5-month mean amplitudes averaged over 1979–2003 are 53.6, 29.9, 15.5, 10.5, and 7.8 DU for the wave number sequence 1, 2, 3, 4 and 5, respectively. For the stationary components the amplitudes are 38.3, 4.8, 1.8, 1.2, 0.7 DU, respectively. Thus, the stationary component of wave 1 and the traveling one of waves 2–5 are predominant. The tendencies in a long-term change in the wave number amplitude can be explained by taking into account the degree of wave deformation of the stratospheric polar vortex edge, net meridional displacements of the lower stratosphere air, and the difference between the total ozone loss and negative trends in the polar and mid-latitude regions. Keywords. General circulation – Middle atmosphere dynamics – Waves and tides

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