The diurnal and semidiurnal tides over Ascension Island (° S, 14° W) and their interaction with the stratospheric quasi-biennial oscillation: studies with meteor radar, eCMAM and WACCM

Davis, Robin; Du, J.; Smith, Anne K.; Ward, W. E.; Mitchell, N. J.

doi:10.5194/acp-13-9543-2013

Cited by 64 publications

(119 citation statements)

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“…The establishment of ground-based radars at both equatorial and polar latitudes enhanced the spatial/temporal coverage originally available from the predominately mid-latitude stations that prevailed before 2000 (e.g. Mitchell et al 2002;Sridharan et al 2010;Nozawa et al 2012;Davis et al 2013). New instruments, notably lidars that provide daytime observations, also came on line (e.g She et al 2002).…”

Section: Atmospheric Tides In the Mltmentioning

confidence: 93%

The dynamics of the mesosphere and lower thermosphere: a brief review

Vincent

2015

Prog. in Earth and Planet. Sci.

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The dynamics of the mesosphere-lower thermosphere (MLT) (60 to 110 km) is dominated by waves and their effects. The basic structure of the MLT is determined by momentum deposition by small-scale gravity waves, which drives a summer-to-winter pole circulation at the mesopause. Atmospheric tides are also an important component of the dynamics of the MLT. Observations from extended ground-based networks, satellites as well as numerical modelling show that non-migrating tidal modes in the MLT are more important than previously thought, with evidence for directly coupling into the thermosphere/ionosphere. Major disturbances lower in the atmosphere, such as wintertime sudden stratospheric warmings, temporarily disrupt the circulation pattern and thermal structure of the MLT. In the equatorial mesosphere, gravity wave driving leads to oscillations in the zonal wind on semiannual time scales, although variability on quasi-biennial time scales is also apparent. Planetary-scale waves such as the quasi-two-day wave temporarily dominate the dynamics of the summertime MLT, especially in the southern hemisphere. Impacts may include short-term changes to the thermal structure and physics of the high-latitude MLT. Here, we briefly review the dynamics of the MLT, with a particular emphasis on developments in the past decade.Keywords: Atmospheric tides; Gravity waves; Planetary waves; Middle atmosphere; Mesosphere; Lower thermosphere; Wave coupling Review IntroductionThe mesosphere-lower thermosphere (MLT) is defined as the region of the atmosphere between about 60 and 110 km in altitude. It constitutes the upper part of what is often referred to as the middle atmosphere (10 to 110 km). The MLT is dominated by the effects of atmospheric waves, including planetary waves, tides and gravity waves. The source regions for these waves are lower in the atmosphere. As the waves propagate upward their amplitudes grow exponentially to compensate for the decrease in atmospheric density (e.g. Andrews et al. 1987). Consequently, wave motions often dominate the wind field in the MLT, so considerable averaging may be required to extract the mean flow, especially that of the mean meridional (NS) motions, which are smaller than the zonal (EW) flow. Zonal-mean zonal winds are eastward (westward) in the winter (summer) middle atmosphere, reaching peak values of approximately 60 to 70 ms −1 near 70 km and Correspondence: robert.vincent@adelaide.edu.au Department of Physics, School of Physical Sciences, University of Adelaide, North Terrace., SA, 5005 Adelaide, Australia then they reduce in magnitude until they reverse sign at heights between 90 and 100 km.Large wave amplitudes lead to wave breaking and hence momentum deposition. This, in turn, produces body forces that drive large scale residual circulations. In the winter stratosphere (approximately 20 to 60 km), planetary wave breaking drives a residual circulation from the equator to the winter pole, while in the mesosphere, gravity wave breaking and dissipation drives a circulation from ...

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Section: Atmospheric Tides In the Mltmentioning

confidence: 93%

The dynamics of the mesosphere and lower thermosphere: a brief review

Vincent

2015

Prog. in Earth and Planet. Sci.

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“…CESM1(WACCM) has been used to simulate the circulation, gravity waves and atmospheric composition changes due to the chemistry and photochemistry in the lower, middle and upper atmosphere (Pedatella et al 2014;Pedatella and Liu 2013;Lu et al 2012;Tan et al 2012a, b, c;Davis et al 2013;Smith et al 2012). Furthermore, it is fully coupled to the land and ocean models (Vertenstein et al 2012).…”

Section: Model Descriptionmentioning

confidence: 99%

Characterising the three-dimensional ozone distribution of a tidally locked Earth-like planet

Proedrou

Hocke

2016

Earth Planet Sp

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We simulate the 3D ozone distribution of a tidally locked Earth-like exoplanet using the high-resolution, 3D chemistryclimate model CESM1(WACCM) and study how the ozone layer of a tidally locked Earth (TLE) (� TLE = 1/365 days) differs from that of our present-day Earth (PDE) (� PDE = 1/1 day). The middle atmosphere reaches a steady state asymptotically within the first 80 days of the simulation. An upwelling, centred on the subsolar point, is present on the day side while a downwelling, centred on the antisolar point, is present on the night side. In the mesosphere, we find similar global ozone distributions for the TLE and the PDE, with decreased ozone on the day side and enhanced ozone on the night side. In the lower mesosphere, a jet stream transitions into a large-scale vortex around a low-pressure system, located at low latitudes of the TLE night side. In the middle stratosphere, the concentration of odd oxygen is approximately equal to that of the ozone [(O x ) ≈ (O 3 )]. At these altitudes, the lifetime of odd oxygen is ∼16 h and the transport processes significantly contribute to the global distribution of stratospheric ozone. Compared to the PDE, where the strong Coriolis force acts as a mixing barrier between low and high latitudes, the transport processes of the TLE are governed by jet streams variable in the zonal and meridional directions. In the middle stratosphere of the TLE, we find high ozone values on the day side, due to the increased production of atomic oxygen on the day side, where it immediately recombines with molecular oxygen to form ozone. In contrast, the ozone is depleted on the night side, due to changes in the solar radiation distribution and the presence of a downwelling. As a result of the reduced Coriolis force, the tropical and extratropical air masses are well mixed and the global temperature distribution of the TLE stratosphere has smaller horizontal gradients than the PDE. Compared to the PDE, the total ozone column global mean is reduced by ∼19.3 %. The day side and the night side total ozone column means are reduced by 23.21 and 15.52 %, respectively. Finally, we present the total ozone column (TOC) maps as viewed by a remote observer for four phases of the TLE during its revolution around the star. The mean TOC values of the four phases of the TLE vary by up to 23 %.

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“…To date, no middle atmosphere model is data-assimilated for the whole domain due to the scarceness of observations in the MLT region. However, there has been effort on using assimilated meteorological analysis data to constrain the middle atmosphere model in the troposphere and stratosphere McLandress et al 2013;Davis et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Climatology of the diurnal tides from eCMAM30 (1979 to 2010) and its comparison with SABER

Gan

Ward

et al. 2014

Earth Planet Space

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The extended Canadian Middle Atmosphere Model (eCMAM) was recently run in a nudged mode using reanalysis data from the ground to 1 hPa for the period of January 1979 to June 2010 (hence the name eCMAM30). In this paper, eCMAM30 temperature is used to examine the background mean temperature, the spectrum of the diurnal tides, and the climatology of the migrating diurnal tide Dw1 and three nonmigrating diurnal tides De3, Dw2, and Ds0 in the stratosphere, mesosphere, and lower thermosphere. The model results are then compared to the diurnal tidal climatology derived from Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) observations between 40 to 110 km and 50°S to 50°N from January 2002 to December 2013. The model reproduces the latitudinal background mean temperature gradients well except that the cold mesopause temperature in eCMAM30 is 10 to 20 K colder than SABER. The diurnal tidal spectra and their relative strengths compare very well between eCMAM30 and SABER. The altitude-latitude structures for the four diurnal tidal components (Dw1, De3, Dw2, and Ds0) from the two datasets are also in very good agreement even for structures in the stratosphere with a weaker amplitude. The largest discrepancy between the model and SABER is associated with the seasonal variation of De3. In addition to the Northern Hemisphere (NH) summer maximum, a secondary maximum occurs during NH winter (December-February) in the model but is absent in SABER. The seasonal variations of the other three diurnal tidal components are in good agreement. Interannual time series of Dw1 and De3 from both eCMAM30 and SABER reveal variability with a period of 25 to 26 months, which indicates the modulation of the diurnal tides by the stratospheric quasi-biennial oscillation (QBO).

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The diurnal and semidiurnal tides over Ascension Island (° S, 14° W) and their interaction with the stratospheric quasi-biennial oscillation: studies with meteor radar, eCMAM and WACCM

Cited by 64 publications

References 73 publications

The dynamics of the mesosphere and lower thermosphere: a brief review

The dynamics of the mesosphere and lower thermosphere: a brief review

Characterising the three-dimensional ozone distribution of a tidally locked Earth-like planet

Climatology of the diurnal tides from eCMAM30 (1979 to 2010) and its comparison with SABER

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