Long-term development of short-period gravity waves in middle Europe

Offermann, D.; Wintel, Johannes; Kalicinsky, Christoph; Knieling, Peter; Koppmann, R.; Steinbrecht, Wolfgang

doi:10.1029/2010jd015544

Cited by 17 publications

(8 citation statements)

References 69 publications

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“…A trend for an increase in gravity wave amplitude has been reported through observations of the gravity wave kinetic energy from both medium frequency and meteor radars through horizontal wind measurements (Hoffmann et al, 2011) at midlatitudes. Other studies have also shown a tendency for the gravity wave activity to increase in the mesosphere and lower thermosphere region (e.g., Offermann et al, 2011;Oliver et al, 2013). It has also been observed from our data that the mean zonal wind during the same period shows an increasing trend at a rate of about 69 ± 24 m/yr (figure not shown here).…”

Section: Possible Connection To Changing Gravity Wave Fluxessupporting

confidence: 88%

Experimental Evidence of Arctic Summer Mesospheric Upwelling and Its Connection to Cold Summer Mesopause

Laskar

Chau

St.-Maurice

et al. 2017

Geophysical Research Letters

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Common volume mesospheric meteor detections from two radar stations separated by about 130 km were used to retrieve horizontal wind fields between 82 and 96 km altitudes at high latitudes, near 69°N. The horizontal wind divergence was estimated from the gradients of the wind fields. This determination is the first of its kind for the mesosphere. Twelve years of nearly continuous data sets reveal systematic summer signatures in the horizontal wind divergence field, namely, a minimum just below the mesopause. There are indications that the horizontal divergence near the mesopause minimum is correlated with the mesopause temperature. Also, the altitude corresponding to the mesospheric divergence minimum tends to increase over the years. We derived the vertical velocity from the horizontal wind divergence at the mesosphere, which shows upward winds peaking near the mesopause. These winds indicate that adiabatic cooling was strongest at the region of the deep temperature minimum seen in the summer mesopause. Common volume mesospheric meteor detections from two radar stations separated by about 130 km were used to retrieve horizontal wind fields between 82 and 96 km altitudes at high latitudes, near 69°N. The horizontal wind divergence was estimated from the gradients of the wind fields. This determination is the first of its kind for the mesosphere. Twelve years of nearly continuous data sets reveal systematic summer signatures in the horizontal wind divergence field, namely, a minimum just below the mesopause. There are indications that the horizontal divergence near the mesopause minimum is correlated with the mesopause temperature. Also, the altitude corresponding to the mesospheric divergence minimum tends to increase over the years. We show that the reversal in the horizontal wind divergence at the mesosphere is consistent with upward winds peaking near the mesopause. These winds indicate that adiabatic cooling was strongest at the region of the deep temperature minimum seen in the summer mesopause. Common volume mesospheric meteor detections from two radar stations separated by about 130 km were used to retrieve horizontal wind fields between 82 and 96 km altitudes at high latitudes, near 69°N. The horizontal wind divergence was estimated from the gradients of the wind fields. This determination is the first of its kind for the mesosphere. Twelve years of nearly continuous data sets reveal systematic summer signatures in the horizontal wind divergence field, namely, a minimum just below the mesopause. There are indications that the horizontal divergence near the mesopause minimum is correlated with the mesopause temperature. Also, the altitude corresponding to the mesospheric divergence minimum tends to increase over the years. We show that the reversal in the horizontal wind divergence at the mesosphere is consistent with upward winds peaking near the mesopause. These winds indicate that adiabatic cooling was strongest at the region of the deep temperature minimum seen in the summer mesopause.

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Section: Possible Connection To Changing Gravity Wave Fluxessupporting

confidence: 88%

Experimental Evidence of Arctic Summer Mesospheric Upwelling and Its Connection to Cold Summer Mesopause

Laskar

Chau

St.-Maurice

et al. 2017

Geophysical Research Letters

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“…It shows a slope of 4.7%/yr (for year 2000, chosen to match reference year chosen for the corresponding calculation with the Hoffmann et al [] data). This compares with the 1.5%/yr reported by Offermann et al [] and the 2–6%/yr computed from the data of Hoffmann et al [] for mesospheric temperature and winds. There are also decadal fluctuations in the GW proxy.…”

Section: Development Of a Gravity Wave Proxysupporting

confidence: 86%

“…Offermann et al [] note that as of year 2011, no conclusive results appear to be available on the long‐term trend in gravity wave activity. They developed a gravity wave (GW) proxy for their mesospheric temperature measurements in terms of the standard deviation about the mean for a given time interval.…”

Section: Development Of a Gravity Wave Proxymentioning

confidence: 99%

Is thermospheric global cooling caused by gravity waves?

2013

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[1] We analyze ion temperature data near 350 km altitude over the years 1966-2012 to seek explanations for three outstanding questions concerning the long-term cooling observed in the upper thermosphere: (1) Why is the cooling so much larger than expected, (2) why has the cooling lasted so long, and (3) why is the thermospheric density response to the cooling so small? We speculate that gravity waves may cause this cooling and provide answers to these questions. Recent simulations have shown that gravity waves are expected to cool the upper thermosphere by an amount comparable to that observed over our data timeline. A gravity wave proxy formed from the nontidal fluctuations in temperature shows a positive long-term trend throughout its timeline, consistent with the increasing cooling observed. The time scales of the long-term trend and its decadal fluctuations are characteristic of the ocean, not the atmosphere. We suggest that the following scenario may explain these behaviors: (a) the climate regime shift of 1976-1977 launched slow Rossby waves across the oceans which continue to propagate to this day, (b) winds over this increasingly corrugated ocean have launched increasing fluxes of gravity waves into the atmosphere, and (c) these increasing fluxes of gravity waves have propagated to the thermosphere to produce increasing amounts of cooling. The strong thermospheric cooling seen would be expected to produce thermospheric density declines much larger than those observed via satellite drag. These temperature and density results would be compatible if the turbopause were lowered 4 km over the time span of observations.

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“…Long‐term trends in winds [e.g., Sridharan et al , 2007; Merzlyakov et al , 2009; Jacobi et al , 2012] and tides [e.g., Vincent et al , 1998; Tsuda et al , 1999; Hagan and Forbes , 2002; Oberheide et al , 2009] are found to vary with location and period of observation. Long‐term studies of gravity wave activity show inter‐annual variability [e.g., Tsuda et al , 2002] and increasing trend [ Offermann et al , 2011; Hoffmann et al , 2011]. Recent studies attempt to summarize decadal variability and trends of the atmospheric parameters in order to get a comprehensive global picture [e.g., Beig et al , 2008].…”

Section: Introductionmentioning

confidence: 99%

Long‐term variability of mean winds in the mesosphere and lower thermosphere at low latitudes

et al. 2012

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[1] Long-term variations of monthly mean zonal and meridional winds in the Mesosphere and Lower Thermosphere (MLT) at low-latitudes are analyzed using four medium frequency (MF) radars and three meteor radars located in the Asia-Oceania region. Radar data taken at close-by latitudes are appended to construct long-term data sets. With this, we have long-term data from five distinct latitudes within AE22 (viz., 22 N, $9 N, 0-2 N, 6-7 S and 21 S). The data length varies at different latitudes and spans a maximum of two decades during 1990-2010. The zonal winds show semiannual oscillation (SAO) at all locations with westward (eastward) winds during equinoxes (solstices). The month height pattern of SAO is similar within AE9and is different at AE22 . The westward winds in the March equinox were enhanced every two or three years during 1990-2002. We define this phenomenon as Mesospheric Quasi-Biennial Enhancement (MQBE). Such signature is not clear after 2002. The meridional winds show annual oscillation (AO), with northward and southward winds during the December and June solstices, respectively. However, the timing at which the wind direction changes does not coincide at all latitudes. The amplitude of the AO is enhanced after 2004 and 2008 at $9 N and $7 S, respectively. Orthogonal components of SAO and AO are detected with persistent phase relation, which suggests that the zonal and meridional winds are coupled. The meridional winds show long-term trends at latitudes of $9 N and $6-7 S, but not at other latitudes . The zonal winds do not show significant long-term trends.Citation: Venkateswara Rao, N., T. Tsuda, D. M. Riggin, S. Gurubaran, I. M. Reid, and R. A. Vincent (2012), Long-term variability of mean winds in the mesosphere and lower thermosphere at low latitudes,

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Long-term development of short-period gravity waves in middle Europe

Cited by 17 publications

References 69 publications

Experimental Evidence of Arctic Summer Mesospheric Upwelling and Its Connection to Cold Summer Mesopause

Experimental Evidence of Arctic Summer Mesospheric Upwelling and Its Connection to Cold Summer Mesopause

Is thermospheric global cooling caused by gravity waves?

Long‐term variability of mean winds in the mesosphere and lower thermosphere at low latitudes

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