Inter-hemispheric mesospheric coupling in a comprehensive middle atmosphere model

Karlsson, Bodil; McLandress, C.; Shepherd, Theodore G.

doi:10.1016/j.jastp.2008.08.006

Cited by 113 publications

(215 citation statements)

References 32 publications

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“…Another possible explanation for the observed summmertime variability in the mesosphere over Rothera could come from planetary wave variability in the winter stratosphere of the northern hemisphere. Becker and Fritts (2006); Karlsson et al (2009) both present modelling studies in which planetary-wave activity in the wintertime stratosphere causes variability in the mesopause of the opposite hemisphere through the shifting of the gravity-wave driven meridional circulation.…”

Section: Discussionmentioning

confidence: 96%

Dynamics of the Antarctic and Arctic mesosphere and lower thermosphere – Part 1: Mean winds

et al. 2010

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Abstract. Zonal and meridional winds have been measured in the upper mesosphere and lower thermosphere at polar latitudes using two ground-based meteor radars. One radar is located at Rothera (68 • S, 68 • W) in the Antarctic and has been operational since February 2005. The second radar is located at Esrange (68 • N, 21 • E) in the Arctic and has been operational since October 1999. Both radars have produced relatively continuous measurements. Here we consider measurements made up to the end of 2009. Both radars are of similar design and at conjugate geographical latitudes, making the results directly comparable and thus allowing investigation of the differences in the mean winds of the Antarctic and Arctic regions. The data from each radar have been used to construct climatologies of monthly-mean zonal and meridional winds at heights between 80 and 100 km. Both Antarctic and Arctic data sets reveal seasonally varying zonal and meridional winds in which the broad pattern repeats from year to year. In particular, the zonal winds display a strong shear in summer associated with the upper part of the westward summertime zonal jet. The winds generally reverse to eastward flow at heights of ∼90 km. The zonal winds are eastward throughout the rest of the year. The meridional winds are generally equatorward over both sites, although brief episodes of poleward flow are often evident near the equinoxes and during winter. The strongest equatorward flows occur at heights of ∼90 km during summer.There are significant differences between the mean winds observed in the Antarctic and Arctic. In particular, the westward winds in summer are stronger and occur earlier in the season in the Antarctic compared with the Arctic. The eastward winds evident above the summertime zonal wind reversal are significantly stronger in the Arctic. The summertime equatorward flow in the Antarctic is slightly weaker, but occurs over a greater depth than is the case in the Arctic.Correspondence to: D. J. Sandford (d.j.sandford@bath.ac.uk) Comparisons of these observations with those of the URAP and HWM-07 empirical models reveal a number of significant differences. In particular, the zonal winds observed in the Antarctic during wintertime are significantly weaker than those of URAP. However, the URAP zonal winds are a good match to the observations of the Arctic. Significant differences are evident between the observations and HWM-07. In particular, the strong wintertime zonal winds of the Arctic in HWM-07 are not evident in the observations and the summertime zonal winds in HWM-07 are systematically stronger than observed. The agreement with meridional winds is generally poor.There is a significant amount of inter-annual variability in the observed zonal and meridional winds. Particularly high variability is observed in the Arctic zonal winds in spring and is probably associated with stratospheric warmings.

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Section: Discussionmentioning

confidence: 96%

Dynamics of the Antarctic and Arctic mesosphere and lower thermosphere – Part 1: Mean winds

et al. 2010

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“…A stronger planetary wave (PW) forcing in the winter stratosphere yields a stronger stratospheric Brewer-Dobson circulation (BDC). This anomalously strong flow yields an anomalously cold stratospheric tropical region and a warm stratospheric winter pole, due to the downward control principle (Karlsson et al, 2009).…”

Section: Introductionmentioning

confidence: 98%

“…Becker and Schmitz, 2003;Becker et al, 2004;Karlsson et al, 2009). This phenomenon, termed interhemispheric coupling (IHC), manifests itself as an anomaly of the zonal mean temperatures.…”

Section: Introductionmentioning

confidence: 99%

“…This weakened meridional flow causes the mesospheric polar winter region to be anomalously cold and the tropical mesosphere to be anomalously warm (Becker and Schmitz, 2003;Becker et al, 2004;Körnich and Becker, 2009).…”

Section: Introductionmentioning

confidence: 99%

“…Central to the hypothesis of IHC is that the increase (or decrease) of the temperature in the tropical mesosphere modifies the temperature gradient between high and low latitudes in the summer mesosphere, which influences the zonal wind in the summer mesosphere, due to thermal wind balance (see e.g. Karlsson et al, 2009;Karlsson and Becker, 2016).…”

Section: Introductionmentioning

confidence: 99%

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

Kuilman

Karlsson

2018

Atmos. Chem. Phys.

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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.

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Summer mesospheric warmings and the quasi 2 day wave

Siskind

McCormack

2014

Geophysical Research Letters

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High‐altitude meteorological analyses are used to study the interannual variability of mesospheric weather in the Southern extratropics over five recent January's (2005, 2006, 2008, 2009, and 2010). Two features are apparent. First, there is significant variability in the quasi 2 day wave (Q2DW) with the largest amplitudes in January 2006 and also the last half of January 2005. Second, these periods coincide with high‐latitude temperature enhancements of 8–12 K. Previous studies have linked summer mesospheric warmings to interhemispheric coupling (IHC); however, the observed temperature and zonal wind anomalies do not agree with the predictions of IHC. Rather it appears that the westward momentum forcing from these Q2DW enhancements counteracts the gravity wave drag forcing which normally produces the cold summer mesopause. Since these temperature increases have been linked to Polar Mesospheric Cloud (PMC) disappearance, the present study supports the suggestion that the Q2DW may be an important factor governing PMC variability.

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Inter-hemispheric mesospheric coupling in a comprehensive middle atmosphere model

Cited by 113 publications

References 32 publications

Dynamics of the Antarctic and Arctic mesosphere and lower thermosphere – Part 1: Mean winds

Dynamics of the Antarctic and Arctic mesosphere and lower thermosphere – Part 1: Mean winds

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

Summer mesospheric warmings and the quasi 2 day wave

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