2021
DOI: 10.5194/acp-2021-981
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Radar observations of winds, waves and tides in the mesosphere and lower thermosphere over South Georgia island (54°S, 36°W) and comparison to WACCM simulations

Abstract: Abstract. The mesosphere and lower thermosphere (MLT) is a dynamic layer of the earth’s atmosphere. This region marks the interface at which neutral atmosphere dynamics begin to influence the ionosphere and space weather. However, our understanding of this region and our ability to accurately simulate it in global circulation models (GCMs) is limited by a lack of observations, especially in remote locations. To this end, a meteor radar was deployed on the remote mountainous island of South Georgia (54° S, 36° … Show more

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Cited by 6 publications
(7 citation statements)
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“…When these secondary GWs break in the winter mesopause region, they exert an eastward drag. According to Becker and Vadas (2018), this effect can explain the observed predominant eastward wind direction in the wintertime mesopause region at middle to high latitudes during medium-to-strong polar vortex periods, as is found in observations (de Wit et al, 2017;Hindley et al, 2022;Hoffmann et al, 2010;Smith, 2012;Stober, Janches, et al, 2021). In turn, the dissipation of secondary GWs leads to the generation of tertiary GWs that can propagate well into the thermosphere .…”
mentioning
confidence: 62%
“…When these secondary GWs break in the winter mesopause region, they exert an eastward drag. According to Becker and Vadas (2018), this effect can explain the observed predominant eastward wind direction in the wintertime mesopause region at middle to high latitudes during medium-to-strong polar vortex periods, as is found in observations (de Wit et al, 2017;Hindley et al, 2022;Hoffmann et al, 2010;Smith, 2012;Stober, Janches, et al, 2021). In turn, the dissipation of secondary GWs leads to the generation of tertiary GWs that can propagate well into the thermosphere .…”
mentioning
confidence: 62%
“…It is now known that the polar vortex broadens with increasing altitude into the upper mesosphere. High-top models such as the Whole Atmosphere Community Climate Model (WACCM) properly simulate the mesospheric polar vortex (MPV) up to middle mesospheric altitudes, but fail to reproduce observations above ~80 km (Harvey et al, 2019;Hindley et al, 2022) especially when the vortex is strong (Harvey et al, 2022). Descent in the polar winter mesosphere, depicted by the arrow in Figure 1 marked "circulation", is part of a global wave-driven pole-to-pole circulation characterized by ascent over the summer pole, cross-equatorial flow from the summer to the winter hemisphere, and descent in the winter high latitudes.…”
Section: Background and Motivationmentioning
confidence: 99%
“…Unfortunately, representation of the polar vortex in the upper mesosphere is generally not accurate in state-of-the-art global models. In fact, in many models the zonal winds blow in the wrong direction in the polar winter upper mesosphere (Eswaraiah et al, 2016;Harvey et al, 2019;Hindley et al, 2022;Lieberman et al, 2015;Liu, 2016;Marsh et al, 2013;Noble et al, 2022;Rüfenacht et al, 2018;Smith, 2012;Yuan et al, 2008;Griffith et al, 2021;McLandress et al, 2006;McCormack et al, 2017;2021;Pedatella et al, 2014;Schmidt et al, 2006;Stober et al, 2021) compared to observations (e.g., Wilhelm et al, 2019) or meteorological analyses that use data assimilation (Eckermann et al, 2018, Stober et al, 2020. Important impacts of this easterly (westward) wind bias are (1) a reduction in the vertical extent of the MPV (Harvey et al, 2019), (2) an increase in the vertical wind shear, which alters the spectrum of GWs and PWs (e.g., Chandran et al, 2013;France et al, 2015), (3) persistent negative meridional potential vorticity gradients at mid-to-high latitudes, which can generate PWs via baroclinic or barotropic instability (e.g., Charney and Stern, 1962), and (4) a reduction in the amplitude of the migrating wavenumber 2 semidiurnal tide (SW2) in Arctic winter (Zhang et al, 2021).…”
Section: The Problemmentioning
confidence: 99%
“…The full-width-half-maxima for these Gaussian weightings are 2 hr in time and 3 km in height. The center of the Gaussian progresses across the data in 1-hr time and 1-km height steps, giving hourly winds between 75 and 105 km (Hindley et al, 2021).…”
Section: Meteor Radarmentioning
confidence: 99%