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.

scholarly journals Forcing mechanisms of the terdiurnal tide

2018 ◽  
Vol 18 (21) ◽  
pp. 15725-15742 ◽  
Author(s):  
Friederike Lilienthal ◽  
Christoph Jacobi ◽  
Christoph Geißler
Keyword(s):  
Gravity Waves ◽  
Middle Atmosphere ◽  
Circulation Model ◽  
Temperature Fields ◽  
Wave Number ◽  
Global Circulation Model ◽  
Solar Forcing ◽  
Global Circulation ◽  
Tidal Interactions ◽  
Forcing Mechanisms

Abstract. Using a nonlinear mechanistic global circulation model we analyze the migrating terdiurnal tide in the middle atmosphere with respect to its possible forcing mechanisms, i.e., the absorption of solar radiation in the water vapor and ozone band, nonlinear tidal interactions, and gravity wave–tide interactions. In comparison to the forcing mechanisms of diurnal and semidiurnal tides, these terdiurnal forcings are less well understood and there are contradictory opinions about their respective relevance. In our simulations we remove the wave number 3 pattern for each forcing individually and analyze the remaining tidal wind and temperature fields. We find that the direct solar forcing is dominant and explains most of the migrating terdiurnal tide's amplitude. Nonlinear interactions due to other tides or gravity waves are most important during local winter. Further analyses show that the nonlinear forcings are locally counteracting the solar forcing due to destructive interferences. Therefore, tidal amplitudes can become even larger for simulations with removed nonlinear forcings.

scholarly journals Forcing Mechanisms of the Terdiurnal Tide

2018 ◽  
Author(s):  
Friederike Lilienthal ◽  
Christoph Jacobi ◽  
Christoph Geißler
Keyword(s):  
Gravity Waves ◽  
Middle Atmosphere ◽  
Circulation Model ◽  
Temperature Fields ◽  
Nonlinear Interactions ◽  
Global Circulation Model ◽  
Solar Forcing ◽  
Global Circulation ◽  
Tidal Interactions ◽  
Forcing Mechanisms

Abstract. Using a nonlinear mechanistic global circulation model we analyze the migrating terdiurnal tide in the middle atmosphere with respect to its possible forcing mechanisms, i.e. the absorption of solar radiation in the water vapor and ozone band, nonlinear tidal interactions, and gravity wave-tide interactions. In comparison to the forcing mechanisms of diurnal and semidiurnal tides, these terdiurnal forcings are less well understood and there are contradictory opinions about their respective relevance. In our simulations we remove the wavenumber 3 pattern for each forcing individually and analyze the remaining tidal wind and temperature fields. We find that the direct solar forcing is dominant and explains most of the migrating terdiurnal tide's amplitude. Nonlinear interactions due to other tides or gravity waves are most important during local winter. Further analyses show that the nonlinear forcings are locally counteracting the solar forcing due to destructive interferences. Therefore, tidal amplitudes can become even larger for simulations with removed nonlinear forcings.

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 On the longitudinal structure of the transient day-to-day variation of the semidiurnal tide in the mid-latitude lower thermosphere − I. Winter season

2001 ◽  
Vol 19 (5) ◽  
pp. 545-562 ◽  
Author(s):  
E. G. Merzlyakov ◽  
Yu. I. Portnyagin ◽  
C. Jacobi ◽  
N. J. Mitchell ◽  
H. G. Muller ◽  
...  
Keyword(s):  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Winter Season ◽  
Semidiurnal Tide ◽  
Longitudinal Structure ◽  
Transient Behaviour ◽  
Meteorology And Atmospheric Dynamics ◽  
S Transform ◽  
Wind Measurements ◽  
Waves And Tides

Abstract. The longitudinal structure of the day-to-day variations of semidiurnal tide amplitudes is analysed based on coordinated mesosphere/lower thermosphere wind measurements at several stations during three winter campaigns. Possible excitation sources of these variations are discussed. Special attention is given to a nonlinear interaction between the semidiurnal tide and the day-to-day mean wind variations. Data processing includes the S-transform analysis which takes into account transient behaviour of secondary waves. It is shown that strong tidal modulations appear during a stratospheric warming and may be caused by aperiodic mean wind variations during this event.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides)

scholarly journals Nonlinear forcing mechanisms of the terdiurnal solar tide and their impact on the zonal mean circulation

2019 ◽  
Author(s):  
Friederike Lilienthal ◽  
Christoph Jacobi
Keyword(s):  
Gravity Wave ◽  
Middle Atmosphere ◽  
Circulation Model ◽  
Wave Drag ◽  
Radiation Absorption ◽  
Global Circulation Model ◽  
Secondary Sources ◽  
Tidal Interactions ◽  
Solar Tide ◽  
Forcing Mechanisms

Abstract. We investigate the forcing mechanisms of the terdiurnal solar tide in the middle atmosphere using a mechanistic global circulation model. In order to quantify their individual contributions, we perform several model experiments and separate each forcing mechanism by switching off the remaining sources. We find that the primary excitation is owing to the terdiurnal component of solar radiation absorption in the troposphere and stratosphere. Secondary sources are nonlinear tide-tide interactions and gravity wave-tide interactions. Thus, although the solar heating clearly dominates the terdiurnal forcing in our simulations, we find that nonlinear tidal and gravity wave interactions contribute in certain seasons and altitudes. By slightly enhancing the different excitation sources, we test the sensitivity of the background circulation on these changes of the dynamics. As a result, the increase of terdiurnal gravity wave drag can strongly affect the middle and upper atmosphere dynamics, including an irregular change of the terdiurnal amplitude, a weakening of neutral winds in the thermosphere, and a significant temperature change in the thermosphere, depending on the strength of the forcing. On the contrary, the influence of nonlinear tidal interactions on the middle atmosphere background dynamics is rather small.

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 Forcing mechanisms of the migrating quarterdiurnal tide

2020 ◽  
Vol 38 (2) ◽  
pp. 527-544 ◽  
Author(s):  
Christoph Geißler ◽  
Christoph Jacobi ◽  
Friederike Lilienthal
Keyword(s):  
Gravity Wave ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Circulation Model ◽  
Destructive Interference ◽  
Global Circulation Model ◽  
Wave Forcing ◽  
Tidal Interactions ◽  
Forcing Mechanisms ◽  
The Individual

Abstract. We used a nonlinear mechanistic global circulation model to analyze the migrating quarterdiurnal tide (QDT) in the middle atmosphere with focus on its possible forcing mechanisms: the absorption of solar radiation by ozone and water vapor, nonlinear tidal interactions, and gravity wave–tide interactions. We show a climatology of the QDT amplitudes, and we examine the contribution of the different forcing mechanisms to the QDT amplitude. To this end, we first extracted the QDT from the model tendency terms and then removed the respective QDT contribution from the different tendency terms. We find that the solar forcing mechanism is the most important one for the QDT; however, the nonlinear and gravity wave forcing mechanisms also play a role in autumn and winter, particularly at lower and middle latitudes in the mesosphere and lower thermosphere. Furthermore, destructive interference between the individual forcing mechanisms is observed. Therefore, tidal amplitudes become even larger in simulations with the nonlinear or gravity wave forcing mechanisms removed.

scholarly journals Nonlinear forcing mechanisms of the migrating terdiurnal solar tide and their impact on the zonal mean circulation

2019 ◽  
Vol 37 (5) ◽  
pp. 943-953 ◽  
Author(s):  
Friederike Lilienthal ◽  
Christoph Jacobi
Keyword(s):  
Gravity Wave ◽  
Middle Atmosphere ◽  
Circulation Model ◽  
Wave Drag ◽  
Radiation Absorption ◽  
Global Circulation Model ◽  
Secondary Sources ◽  
Tidal Interactions ◽  
Solar Tide ◽  
Forcing Mechanisms

Abstract. We investigate the forcing mechanisms of the terdiurnal solar tide in the middle atmosphere using a mechanistic global circulation model. In order to quantify their individual contributions, we perform several model experiments and separate each forcing mechanism by switching off the remaining sources. We find that the primary excitation is owing to the terdiurnal component of solar radiation absorption in the troposphere and stratosphere. Secondary sources are nonlinear tide–tide interactions and gravity wave–tide interactions. Thus, although the solar heating clearly dominates the terdiurnal forcing in our simulations, we find that nonlinear tidal and gravity wave interactions contribute in certain seasons and at certain altitudes. By slightly enhancing the different excitation sources, we test the sensitivity of the background circulation to these changes of the dynamics. As a result, the increase of terdiurnal gravity wave drag can strongly affect the middle and upper atmosphere dynamics, including an irregular change of the terdiurnal amplitude, a weakening of neutral winds in the thermosphere, and a significant temperature change in the thermosphere, depending on the strength of the forcing. On the contrary, the influence of nonlinear tidal interactions on the middle atmosphere background dynamics is rather small.

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