Interhemispheric differences of mesosphere–lower thermosphere winds and tides investigated from three whole-atmosphere models and meteor radar observations

Stober, Gunter; Kuchař, Aleš; Pokhotelov, Dimitry; Liu, Huixin; Liu, Hanli; Schmidt, Hauke; Jacobi, Ch.; Baumgarten, Kathrin; Brown, Peter; Janches, Diego; Murphy, D. J.; Kozlovsky, Alexander; Lester, M.; Belova, Evgenia; Kero, Johan; Mitchell, N. J.

doi:10.5194/acp-21-13855-2021

Cited by 48 publications

(71 citation statements)

References 98 publications

(137 reference statements)

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Section: Evaluation Of Navgem‐ha Resultssupporting

confidence: 91%

“…The wind maxima are the strongest at TDF and KEP, and are weaker at ROT and DAV at higher latitudes, showing the amplitude change of the oscillation with latitude. These features are all consistent with properties of semidiurnal tides reported before (e.g., Murphy et al, 2006;Stober et al, 2021). Figure 10 shows that the semidiurnal tidal amplitudes from NAVGEM-HA are greater than those observed by the radars at TDF, KEP, and KSS but the tidal amplitudes are similar at ROT and DAV.…”

Section: Wind and Tidal Variations During The Sswsupporting

confidence: 87%

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Mesosphere and Lower Thermosphere Winds and Tidal Variations During the 2019 Antarctic Sudden Stratospheric Warming

Liu

Janches

et al. 2022

JGR Space Physics

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Realistic modeling of the winds and dynamical variations in the mesosphere and lower thermosphere (MLT) at Southern Hemisphere (SH) mid‐to‐high latitudes near 60°S where dramatic motions occur has been a challenge. This work presents an evaluation of the MLT zonal and meridional winds from ∼80 to 98 km altitude produced by the high‐altitude version of the Navy Global Environmental Model (NAVGEM‐HA) numerical weather prediction system during the Antarctic Sudden Stratospheric Warming (SSW) in September 2019. These results are compared with the coincident measurements by five meteor radars at Tierra del Fuego (TDF; 53.7°S, 67.7°W), King Edward Point (KEP; 54.3°S, 36.5°W), King Sejong Station (KSS; 62.2°S, 58.8°W), Rothera (ROT; 67.5°S, 68.0°W), and Davis (DAV; 68.6°S, 78.0°E) across SH mid‐to‐high latitudes. We find that the day‐to‐day variations in NAVGEM‐HA winds related to tidal motions are overall consistent with variations in the radar winds, and the daily mean winds have a correlation of 0.7–0.9 between them. Three‐hourly NAVGEM‐HA winds have a correlation of ∼0.5 and mean difference <10 m/s to the radar observations at most stations, and the Root Mean Square (RMS) error ranges from ∼25 to 35 m/s. Above 90 km altitude, the correlation coefficient decreases, and the difference and RMS error increase, indicating an upper limit to the validity of the NAVGEM‐HA results. Both the analyzed and observed winds reveal an enhancement in diurnal and semidiurnal tidal amplitude during this SH SSW. NAVGEM‐HA shows some evidence that nonmigrating tidal enhancements are produced through the interaction of migrating tides with planetary waves.

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Section: Evaluation Of Navgem‐ha Resultssupporting

confidence: 91%

Section: Wind and Tidal Variations During The Sswsupporting

confidence: 87%

Mesosphere and Lower Thermosphere Winds and Tidal Variations During the 2019 Antarctic Sudden Stratospheric Warming

Liu

Janches

et al. 2022

JGR Space Physics

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“…This is consistent with other meteor radar wind observations at high latitudes in both hemispheres (e.g. Fritts et al, 2010b;Sandford et al, 2010;Stober et al, 2021b). The vertical gradient of the zonal wind in summer is particularly strong, from around -20 ms -1 (westward) to up to +40 ms -1 (eastward) over only 10 to 15 km altitude.…”

Section: Comparison To a Traditional Height Gates Approachsupporting

confidence: 92%

“…Westward wintertime winds in the simulated polar MLT are a long-standing feature of WACCM (Harvey et al, 2019;Ramesh et al, 2020;Stober et al, 2021b), and they are also found in the thermospheric extension WACCM-X (Liu et al, 2010;Pedatella et al, 2014;Liu et al, 2018;Pancheva et al, 2020) and in other high-top models such as the MUAM (Lilienthal et al, 2018).…”

Section: Secondary Gws and Differences Between Radar Observations And Waccmmentioning

confidence: 84%

“…Although not all global models currently show this feature, models that do simulate the observed eastward winds in winter may each have other biases of their own in other altitude regions, as shown by Pedatella et al (2014) and more recently by Stober et al (2021b). Careful tuning of the GW parameterisation scheme in WACCM may likely produce a closer agreement to the observations for a given season, however this may give rise to other biases in different regions and seasons.…”

Section: Secondary Gws and Differences Between Radar Observations And Waccmmentioning

confidence: 99%

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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

Hindley

Cobbett

Fritts

et al. 2021

Preprint

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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° W) in the Southern Ocean from 2016 to 2020. The goal of this study is to use these new measurements to characterise the fundamental dynamics of the MLT above South Georgia including large-scale winds, solar tides, planetary waves (PWs) and mesoscale gravity waves (GWs). We first present an improved method for time-height localisation of radar wind measurements and characterise the large-scale MLT winds. We then explore the amplitudes and phases of the diurnal (24 h), semidiurnal (12 h) and terdiurnal (8 h) solar tides at this latitude. We also explore PW activity and find very large amplitudes up to 30 ms−1 for the quasi-2 day wave in summer and show that the dominant modes of the quasi-5, 10 and 16 day waves are westward W1 and W2. We investigate wind variance due to GWs in the MLT and use a new method to show an east-west tendency of GW variance of up to 20 % during summer and a weaker north-south tendency of 0–5 % during winter. This is contrary to the expected tendency of GW directions in the winter stratosphere below, which is a strong suggestion of secondary GW (2GW) observations in the MLT. Lastly, comparison of radar winds to a climatological Whole Atmosphere Community Climate Model (WACCM) simulation reveals a simulated summertime mesopause and zonal wind shear that occur at altitudes around 10 km lower than observed, and southward winds during winter above 90 km altitude in the model that are not seen in observations. Further, wintertime zonal winds above 85 km altitude are eastward in radar observations but in WACCM they are found to weaken and reverse to westward. Recent studies have linked this discrepancy to the impact of 2GWs on the residual circulation which are not included in WACCM. These measurements therefore provide vital constraints that can guide the development of GCMs as they extend upwards into this important region of the atmosphere.

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A meteor radar network study on the polar-to-tropical mesospheric coupling during the 2018 Sudden Stratosphere Warming

Eswaraiah

Seo

Kumar

et al. 2022

Preprint

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Using advanced meteor radar network observations along with ERA5 data, we report observational evidence of polar to tropical mesospheric teleconnections during the 2018 major sudden stratosphere warming (SSW) event in the northern hemisphere. A peak SSW on February 14, 2018, characterized by a ˜45 K rise in polar stratosphere temperature and a zonal wind reversal of ˜(-25) m/s at 60°N and 10 hPa, is observed. In the tropical lower mesosphere, a maximum zonal wind reversal (-24 m/s) compared with that identified in the extra-tropical regions was observed. Moreover, a time delay in the wind reversal between the tropical/polar stations and the mid-latitudes was detected. The wind reversal in the mesosphere is due to the propagation of dominant intra-seasonal oscillations (ISOs) of 30-60-days and the presence and superposition of 8-day period planetary waves (PWs). The ISOs phase propagation is observed from the high-to low-latitudes (60 °N to 20 °N) in contrast to 8-day PWs phase propagation, indicating the change in the meridional propagation of winds during SSW. However, the superposition of dominant ISOs and weak 8-day PWs could be responsible for the delay of the wind reversal in the tropical mesosphere. Therefore, this study has strong implications for understanding the reversed (polar to tropical) mesospheric meridional circulation during SSW.

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Interhemispheric differences of mesosphere–lower thermosphere winds and tides investigated from three whole-atmosphere models and meteor radar observations

Cited by 48 publications

References 98 publications

Mesosphere and Lower Thermosphere Winds and Tidal Variations During the 2019 Antarctic Sudden Stratospheric Warming

Mesosphere and Lower Thermosphere Winds and Tidal Variations During the 2019 Antarctic Sudden Stratospheric Warming

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

A meteor radar network study on the polar-to-tropical mesospheric coupling during the 2018 Sudden Stratosphere Warming

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