Summer mesospheric warmings and the quasi 2 day wave

Siskind, D. E.; McCormack, J. P.

doi:10.1002/2013gl058875

Cited by 30 publications

(27 citation statements)

References 24 publications

(53 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This may be attributable to strong variability in the summer hemisphere MLT region and may impact the IHC mechanism where the perturbations are needed to propagate through the mesosphere and lower thermosphere from the equator to the summer pole-a mechanism that remains unclear, as noted by Tan et al [2012] The summer mesospheric warmings may not be due solely to IHC. As noted by Pendlebury [2012] and Siskind and McCormack [2014], a strong westward drag by the QTDW in the summer hemisphere may partially negate the eastward GW drag that is seen climatologically atop the summer westward jet (e.g., Figures 5b and 6b). A diminished GW drag would reduce the summer polar upwelling and result in anomalous warming near the summer mesopause.…”

Section: Discussionmentioning

confidence: 78%

On the composite response of the MLT to major sudden stratospheric warming events with elevated stratopause

et al. 2016

View full text Add to dashboard Cite

Based on a climate-chemistry model (constrained by reanalyses below~50 km), the zonal-mean composite response of the mesosphere and lower thermosphere (MLT) to major sudden stratospheric warming events with elevated stratopauses demonstrates the role of planetary waves (PWs) in driving the mean circulation in the presence of gravity waves (GWs), helping the polar vortex recover and communicating the sudden stratospheric warming (SSW) impact across the equator. With the SSW onset, strong westward PW drag appears above 80 km primarily from the dissipation of wave number 1 perturbations with westward period of 5-12 days, generated from below by the unstable westward polar stratospheric jet that develops as a result of the SSW. The filtering effect of this jet also allows eastward propagating GWs to saturate in the winter MLT, providing eastward drag that promotes winter polar mesospheric cooling. The dominant PW forcing translates to a net westward drag above the eastward mesospheric jet, which initiates downwelling over the winter pole. As the eastward polar stratospheric jet returns, this westward PW drag persists above 80 km and acts synergistically with the return of westward GW drag to drive a stronger polar downwelling that warms the pole adiabatically and helps reform the stratopause at an elevated altitude. With the polar wind reversal during the SSW onset, the westward drag by the quasi-stationary PW in the winter stratosphere drives an anomalous equatorial upwelling and cooling that enhance tropical stratospheric ozone. Along with equatorial wind anomalies, this ozone enhancement subsequently amplifies the migrating semidiurnal tide amplitude in the winter midlatitudes.

show abstract

Section: Discussionmentioning

confidence: 78%

On the composite response of the MLT to major sudden stratospheric warming events with elevated stratopause

et al. 2016

View full text Add to dashboard Cite

show abstract

“…In large amplitude QTDW years, the brightness of southern PMC is reduced. Siskind and McCormack (2014) ascribe this effect to the QTDW depositing westward momentum that, acting through the Coriolis torque in Equation one, produces a southward flow that partially offsets the GW-driven equatorward, northward wind. Hence, there is a corresponding reduction in the upward motions at the pole with an accompanying reduction in the adiabatic cooling, leading to a temperature increase at the polar mesopause.…”

mentioning

confidence: 99%

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

Vincent

2015

Prog. in Earth and Planet. Sci.

View full text Add to dashboard Cite

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 ...

show abstract

“…Since variability in the summer stratospheric zonal flow is also related to the IHC mechanism, the two phenomena should be closely coupled, as suggested by Gu et al (2016). An indication of their interconnection is given by the following studies: (a) Karlsson et al (2007) found a strong anticorrelation between the noctilucent cloud occurrence and high-latitude winter stratospheric temperatures and (b) Siskind and McCormack (2014) sought revision of the theory behind the IHC since they could not find indications of the conventional temperature and wind patterns associated with the proposed IHC mechanism. In the light of these findings, we hypothesize that while the Q2DW is associated with an enhanced PW activity in the winter hemisphere as suggested by e.g.…”

Section: Introductionmentioning

confidence: 93%

The role of the winter residual circulation in the summer mesopause regions in WACCM

Kuilman

Karlsson

2018

Atmos. Chem. Phys.

View full text Add to dashboard Cite

Abstract. High winter planetary wave activity warms the summer polar mesopause via a link between the two hemispheres. Complex wave-mean-flow interactions take place on a global scale, involving sharpening and weakening of the summer zonal flow. Changes in the wind shear occasionally generate flow instabilities. Additionally, an altering zonal wind modifies the breaking of vertically propagating gravity waves. A crucial component for changes in the summer zonal flow is the equatorial temperature, as it modifies latitudinal gradients. Since several mechanisms drive variability in the summer zonal flow, it can be hard to distinguish which one is dominant. In the mechanism coined interhemispheric coupling, the mesospheric zonal flow is suggested to be a key player for how the summer polar mesosphere responds to planetary wave activity in the winter hemisphere. We here use the Whole Atmosphere Community Climate Model (WACCM) to investigate the role of the summer stratosphere in shaping the conditions of the summer polar mesosphere. Using composite analyses, we show that in the absence of an anomalous summer mesospheric temperature gradient between the equator and the polar region, weak planetary wave forcing in the winter would lead to a warming of the summer mesosphere region instead of a cooling, and vice versa. This is opposing the temperature signal of the interhemispheric coupling that takes place in the mesosphere, in which a cold and calm winter stratosphere goes together with a cold summer mesopause. We hereby strengthen the evidence that the variability in the summer mesopause region is mainly driven by changes in the summer mesosphere rather than in the summer stratosphere.

show abstract

Summer mesospheric warmings and the quasi 2 day wave

Cited by 30 publications

References 24 publications

On the composite response of the MLT to major sudden stratospheric warming events with elevated stratopause

On the composite response of the MLT to major sudden stratospheric warming events with elevated stratopause

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

The role of the winter residual circulation in the summer mesopause regions in WACCM

Contact Info

Product

Resources

About