Global wave activity from upper stratosphere to lower thermosphere: A new turbopause concept

Offermann, D.; Jarisch, M.; Oberheide, J.; Gusev, Oleg; Wohltmann, Ingo; Russell, James M.; Mlynczak, Martin G.

doi:10.1016/j.jastp.2006.01.013

Cited by 31 publications

(86 citation statements)

References 53 publications

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“…In contrast to the paper of Offermann et al (2006) there is no indication of a dramatic change in the temperature fluctuations in the upper mesosphere in our data, which also vary with the season. Only between March and September the fluctuations increase up to 70 km slowly and above strongly.…”

Section: Discussioncontrasting

confidence: 99%

Seasonal changes in gravity wave activity measured by lidars at mid-latitudes

2008

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Apart from some gaps due to the adverse weather conditions the measurements are well distributed throughout the year. Comprehensive information about the activity of mediumand low-frequency gravity waves was extracted from this data set. The dominating vertical wavelengths found are between 10 and 20 km and do not show any seasonal variation. In contrast the temperature fluctuations due to gravity waves experience a clear annual cycle with a maximum in winter. The most significant differences exist around 60 km where the fluctuations in winter are more than two times larger than they are in summer. Only small seasonal differences are observed above 90 km and below 35 km. Generally, the fluctuations grow from about 0.5 K up to 8 K between 20 and 100 km. Damping of waves is observed at nearly all altitudes and in all seasons. The planetary wave activity shows a similar structure in altitude and season as the gravity wave activity which indicates that similar mechanisms influencing different scales. Combining the monthly mean temperatures and the fluctuations we show that the transition between winter and summer season and vice versa seems to start in the mesopause region and to penetrate downward.

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Section: Discussioncontrasting

confidence: 99%

Seasonal changes in gravity wave activity measured by lidars at mid-latitudes

2008

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“…This may explain the maximum variability near the mesopause identified from TIMED/ SABER temperature observations (''wave turbopause'' [Offermann et al, 2006]). Because N and the winds change rapidly in this relatively thin region ( 10 km), the impact of the wave breaking may be poorly represented in global models which could result in a weaker residual mean circulation.…”

Section: Resultsmentioning

confidence: 97%

On the large wind shear and fast meridional transport above the mesopause

Liu

2007

Geophysical Research Letters

111

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[1] Unexpectedly strong winds/shears and fast meridional transport above the mesopause have been revealed from previous rocket and satellite observations. Using Richardson number criteria for dynamic stability, we estimate the maximum wind shears allowable by the background static stability, which peaks above the mesopause. These maximum shears are in general agreement with the large wind shears inferred from the rocket measurements at low and mid-latitudes, indicating the close relationship between the latter and the stability constraint set by the background atmosphere. Diagnostic calculations also indicate that the meridional transport in this region may not be well understood solely by examining the mean meridional circulation, and large amplitude tides/ planetary waves can play an important role in the bulk transport of tracers. Strong stochastic winds, presumably due to gravity waves, do not seem to significantly change the large scale pattern of the transport but may extend the range of the tracer movement.On the large wind shear and fast meridional transport above the mesopause, Geophys. Res. Lett., 34, L08815,

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“…A similar expression has been used to determine the classical radar turbopause (e.g., Hall et al, 2008). An alternative wave turbopause was suggested by Offermann et al (2006Offermann et al ( , 2007Offermann et al ( , 2009) based on the steep increase in the variance of satellite temperature profiles near 95 km. It appears that different type of measurements define their own turbopause.…”

Section: Introductionmentioning

confidence: 99%

The Turbopause experiment: atmospheric stability and turbulent structure spanning the turbopause altitude

et al. 2011

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Abstract. Very few sequences of high resolution wind and temperature measurements in the lower thermosphere are available in the literature, which makes it difficult to verify the simulation results of models that would provide better understanding of the complex dynamics of the region. To address this problem the Turbopause experiment used four rockets launched over a period of approximately two hours from Poker Flat Research Range, Alaska (64 • N, 147 • W) on the night of 17-18 February 2009. All four rocket payloads released trimethyl aluminum trails for neutral wind and turbulence measurements, and two of the rockets carried ionization gauges and fixed-bias Langmuir probes measuring neutral and electron densities, small-scale fluctuations and neutral temperatures. Two lidars monitored temperature structure and sodium densities. The observations were made under quiet geomagnetic conditions and show persistence in the wind magnitudes and shears throughout the observing period while being modulated by inertia-gravity waves. High resolution temperature profiles show the winter polar mesosphere and lower thermosphere in a state of relatively low stability with several quasi-adiabatic layers between 74 and 103 km. Temperature and wind data were combined to calculate Richardson number profiles. Evidence for turbulence comes from simultaneous observations of density fluctuations and downward transport of sodium in a mixed layer near 75 km; the observation of turbulent fluctuations and energy dissipation from 87-90 km; and fast and irregular trail expansion at 90-93 km, and especially between 95 to 103 km. The regions of turbulent trails agree well with regions of quasi-adiabatic temperature gradients. Above Correspondence to: G. A. Lehmacher (glehmac@clemson.edu) 103 km, trail diffusion was mainly laminar; however, unusual features and vortices in the trail diffusion were observed up to 118 km that have not been as prevalent or as clearly evident in earlier trail releases.

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Global wave activity from upper stratosphere to lower thermosphere: A new turbopause concept

Cited by 31 publications

References 53 publications

Seasonal changes in gravity wave activity measured by lidars at mid-latitudes

Seasonal changes in gravity wave activity measured by lidars at mid-latitudes

On the large wind shear and fast meridional transport above the mesopause

The Turbopause experiment: atmospheric stability and turbulent structure spanning the turbopause altitude

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