Long-term variability of mid-latitude mesosphere-lower thermosphere winds over Collm (51°N, 13°E)

Jacobi, Christoph; Lilienthal, Friederike; Geißler, Christoph; Krug, Amelie

doi:10.1016/j.jastp.2015.05.006

Cited by 31 publications

(38 citation statements)

References 33 publications

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“…At 110 km the deviation increases up to 5 km, whereas the highest logarithmic pressure level of about 160 km may correspond to a geometrical height between 300 and 400 km. In the lowermost 10 km, zonal mean temperatures are nudged to the 2000-2010 mean monthly mean ERA-Interim (Dee et al, 2011) zonal mean temperatures to correct the climatology of the troposphere, which is not included in the model in detail (Jacobi et al, 2015;Lilienthal et al, 2018). Furthermore, at 1000 hPa, which defines the lower boundary of the model, SPWs with wave numbers 1, 2 and 3 are forced, which are extracted from the 2000-2010 mean ERA-Interim monthly temperature and geopotential reanalysis data.…”

Section: Model Description and Setupmentioning

confidence: 99%

“…The horizontal resolution of the model is 5 • in latitude and 5.625 • in longitude and the vertical resolution is 2.842 km. The model solves the primitive equations in flux form (e.g., Jakobs et al, 1986). MUAM includes parameterizations to simulate subgrid processes such as GWs, absorption of solar radiation or infrared cooling.…”

Section: Model Description and Setupmentioning

confidence: 99%

“…GWs are parameterized after an updated linear scheme (Lindzen, 1981;Jakobs et al, 1986) with multiple breaking levels (Fröhlich et al, 2003b;Jacobi et al, 2006). GW amplitudes are included at an altitude of 10 km as a zonal mean with a global average of 1 cm s −1 for the vertical velocity perturbation.…”

Section: Model Description and Setupmentioning

confidence: 99%

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Effect of latitudinally displaced gravity wave forcing in the lower stratosphere on the polar vortex stability

et al. 2019

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Abstract. In order to investigate the impact of a locally confined gravity wave (GW) hotspot, a sensitivity study based on simulations of the middle atmosphere circulation during northern winter was performed with a nonlinear, mechanistic, general circulation model. To this end, we selected a fixed longitude range in the East Asian region (120–170∘ E) and a latitude range from 22.5 to 52.5∘ N between 18 and 30 km for the hotspot region, which was then shifted northward in steps of 5∘. For the southernmost hotspots, we observe a decreased stationary planetary wave (SPW) with wave number 1 (SPW 1) activity in the upper stratosphere and lower mesosphere, i.e., fewer SPWs 1 are propagating upwards. These GW hotspots lead to a negative refractive index, inhibiting SPW propagation at midlatitudes. The decreased SPW 1 activity is connected to an increased zonal mean zonal wind at lower latitudes. This, in turn, decreases the meridional potential vorticity gradient (qy) from midlatitudes towards the polar region. A reversed qy indicates local baroclinic instability, which generates SPWs with wave number 1 in the polar region, where we observe a strong positive Eliassen–Palm (EP) divergence. As a result, the EP flux increases towards the polar stratosphere (corresponding to enhanced SPW 1 amplitudes), where the SPWs with wave number 1 break, and the zonal mean zonal wind decreases. Thus, the local GW forcing leads to a displacement of the polar vortex towards lower latitudes. The effect of the local baroclinic instability indicated by the reversed qy also produces SPWs with wave number 1 in the lower mesosphere. The effect on the dynamics in the middle atmosphere due to GW hotspots that are located northward of 50∘ N is negligible, as the refractive index of the atmosphere is strongly negative in the polar region. Thus, any changes in the SPW activity due to the local GW forcing are quite ineffective.

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Section: Model Description and Setupmentioning

confidence: 99%

Section: Model Description and Setupmentioning

confidence: 99%

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Effect of latitudinally displaced gravity wave forcing in the lower stratosphere on the polar vortex stability

et al. 2019

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“…Mesosphere and lower thermosphere winds have been measured using meteor radar from 2004 to present and the low-frequency (LF) drift method (Jacobi, Arras, et al, 2009) from 1979to 2008. These wind data were combined to obtain a homogeneous long-term data set of the mesosphere and lower thermosphere winds at 90 km (Jacobi et al, 2015). In this study, we use the wind data from 1980 to 2014, the same period as the WACCM-X simulation period.…”

Section: Wind Datamentioning

confidence: 99%

Trends and Solar Irradiance Effects in the Mesosphere

2019

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We investigate trends and solar irradiance effects in the mesosphere using the Whole Atmosphere Community Climate Model with eXtended thermosphere and ionosphere (WACCM‐X) and radar measurements of winds at Collm (51°N, 13°E), for the period of 1980–2014. We found that in the mesosphere, dynamics significantly impact temperature and wind trends, as well as how solar irradiance affects the temperature and winds. The global average temperature trends are negative, with a maximum of ~−1 K per decade in the middle to lower mesosphere. Solar irradiance effects on the global average temperature are positive and decrease monotonically with decreasing altitude, changing from ~3 K/100 solar flux units (sfu) near the mesopause to ~1 K per 100 sfu in the lower mesosphere. In the summer upper mesosphere, temperature trends can become near 0 or positive, likely due to dynamical effects. Both wind trends and solar effects on the winds show dynamical patterns with negative and positive values, indicating that they are predominantly controlled by dynamics. The wind trends and solar effects on the winds are on the orders of ~±5 m/s per decade and ~±5 m/s per 100 sfu, respectively, and they are not as statistically significant as their temperature counterparts. At Collm (51°N, 13°E), the observed zonal winds at 90 km have a larger trend of 1.98 m/s per decade compared to the simulated zonal winds and it is statistically significant, but both the simulated and observed meridional winds do not have statistically significant trends.

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“…Vertical spacing is about 2.8 km, and consequently, the upper boundary is located at z 56 ≈ 160 km. The lower levels up to 30 km height are nudged with 2000-2010 mean monthly mean ERA-Interim zonal mean temperature fields to correctly represent the dynamics in the lower atmosphere (Jacobi et al, 2015;Lilienthal et al, 2018). Solar and infrared radiative processes are parameterized according to the works by Strobel (1978) and Fomichev and Shved (1985), respectively.…”

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confidence: 99%

Interaction of Small-Scale Gravity Waves with the Terdiurnal Solar Tide in the Mesosphere and Lower Thermosphere

Lilienthal

Yiğit

Samtleben

et al. 2020

Preprint

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Abstract. Implementing a nonlinear whole atmosphere gravity wave (GW) parameterization into the Middle and Upper Atmosphere Model extending to the lower thermosphere (160 km), we study the response of the atmosphere in terms of the circulation patterns, temperature distribution, and migrating terdiurnal solar tide activity to the upward propagating small-scale internal GWs originating in the lower atmosphere. We perform three test simulations for the Northern Hemisphere winter conditions in order to assess the effects of variations in the initial GW spectrum on the dynamics of the mesosphere and lower thermosphere. We find that the overall strength of the source level momentum flux has a comparatively small impact on zonal mean dynamics. The tails of the GW source level spectrum, however, are crucial for the lower thermosphere dynamics. With respect to the terdiurnal tide, we find a strong dependence of tidal amplitude on the induced GW drag, generally being larger when GW drag is increased.

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Long-term variability of mid-latitude mesosphere-lower thermosphere winds over Collm (51°N, 13°E)

Cited by 31 publications

References 33 publications

Effect of latitudinally displaced gravity wave forcing in the lower stratosphere on the polar vortex stability

Effect of latitudinally displaced gravity wave forcing in the lower stratosphere on the polar vortex stability

Trends and Solar Irradiance Effects in the Mesosphere

Interaction of Small-Scale Gravity Waves with the Terdiurnal Solar Tide in the Mesosphere and Lower Thermosphere

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