The “wave turbopause”

Offermann, D.; Jarisch, M.; Schmidt, Hauke; Oberheide, J.; Grossmann, K. U.; Gusev, Oleg; Russell, James M.; Mlynczak, Martin G.

doi:10.1016/j.jastp.2007.05.012

Cited by 29 publications

(78 citation statements)

References 36 publications

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“…As the model includes a full formulation of tropospheric dynamics and physics, it is producing internal variability in a wide range of frequencies. It has been shown that the model variability compares well with observed atmospheric variability in the cases of the northern winter stratosphere , and of the global mesosphere and lower thermosphere (Offermann et al, 2007). The model dynamics and physics are interactively coupled with the MOZART3 chemistry scheme (Kinnison et al, 2007) that includes 48 compounds and 153 gas phase reactions in this version.…”

Section: Description Of the Model And Model Experimentsmentioning

confidence: 92%

The effect of the solar rotational irradiance variation on the middle and upper atmosphere calculated by a three-dimensional chemistry-climate model

2009

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Abstract. This paper analyzes the effects of the solar rotational (27-day) irradiance variations on the chemical composition and temperature of the stratosphere, mesosphere and lower thermosphere as simulated by the three-dimensional chemistry-climate model HAMMONIA. Different methods are used to analyze the model results, including high resolution spectral and cross-spectral techniques. To force the simulations, an idealized irradiance variation with a constant period of 27 days (apparent solar rotation period) and with constant amplitude is used. While the calculated thermal and chemical responses are very distinct and permanent in the upper atmosphere, the responses in the stratosphere and mesosphere vary considerably in time despite the constant forcing. The responses produced by the model exhibit a non-linear behavior: in general, the response sensitivities (not amplitudes) decrease with increasing amplitude of the forcing. In the extratropics the responses are, in general, seasonally dependent with frequently stronger sensitivities in winter than in summer. Amplitude and phase lag of the ozone response in the tropical stratosphere and lower mesosphere are in satisfactory agreement with available observations. The agreement between the calculated and observed temperature response is generally worse than in the case of ozone.

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Section: Description Of the Model And Model Experimentsmentioning

confidence: 92%

The effect of the solar rotational irradiance variation on the middle and upper atmosphere calculated by a three-dimensional chemistry-climate model

2009

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“…Contour interval is 5 m 2 /s diffusion coefficient varies depending on the mass of the chemical species in question, it is now recognized that there is no single homopause. Offermann et al (2007) used standard deviations of temperature as a function of altitude in global data to identify a transition they labeled the wave turbopause. The concept behind their analysis is that, in the middle atmosphere where waves are damped by turbulent processes, the variance will not grow with height at the rate for a conserved wave of exp(z/2H), where z is altitude and H is scale height.…”

Section: Diffusionmentioning

confidence: 99%

“…However, when the damping ceases at the turbopause, the variance can grow much more rapidly. Using this transition as a signature of the wave turbopause, Offermann et al (2007) found a clearly defined wave turbopause that varied with latitude and season over the range from about 80 to 100 km.…”

Section: Diffusionmentioning

confidence: 99%

Global Dynamics of the MLT

2012

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The transition between the middle atmosphere and the thermosphere is known as the MLT region (for mesosphere and lower thermosphere). This area has some characteristics that set it apart from other regions of the atmosphere. Most notably, it is the altitude region with the lowest overall temperature and has the unique characteristic that the temperature is much lower in summer than in winter. The summer-to-winter-temperature gradient is the result of adiabatic cooling and warming associated with a vigorous circulation driven primarily by gravity waves. Tides and planetary waves also contribute to the circulation and to the large dynamical variability in the MLT. The past decade has seen much progress in describing and understanding the dynamics of the MLT and the interactions of dynamics with chemistry and radiation. This review describes recent observations and numerical modeling as they relate to understanding the dynamical processes that control the MLT and its variability. Results from the Whole Atmosphere Community Climate Model (WACCM), which is a comprehensive high-top general circulation model with interactive chemistry, are used to illustrate the dynamical processes. Selected observations from the Sounding the Atmosphere with Broadband Emission Radiometry (SABER) instrument are shown for comparison. WACCM simulations of MLT dynamics have some differences with observations. These differences and other questions and discrepancies described in recent papers point to a number of ongoing uncertainties about the MLT dynamical system.

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“…McIntyre, 1991) and thus generation of turbulence. Indeed, the concept of a "wave turbopause" was proposed by Offermann et al (2007) and compared with the method used forthwith by Hall et al (2008). Prevailing winds filter or even inhibit propagation of gravity waves generated in the lower atmosphere, and the static stability (or lack of it) of the atmosphere dictates the vertical distribution of gravity wave saturation and breaking.…”

Section: Introductionmentioning

confidence: 99%

Change in turbopause altitude at 52 and 70° N

Hall¹,

Holmen

Meek

et al. 2016

Atmos. Chem. Phys.

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Abstract. The turbopause is the demarcation between atmospheric mixing by turbulence (below) and molecular diffusion (above). When studying concentrations of trace species in the atmosphere, and particularly long-term change, it may be important to understand processes present, together with their temporal evolution that may be responsible for redistribution of atmospheric constituents. The general region of transition between turbulent and molecular mixing coincides with the base of the ionosphere, the lower region in which molecular oxygen is dissociated, and, at high latitude in summer, the coldest part of the whole atmosphere.This study updates previous reports of turbopause altitude, extending the time series by half a decade, and thus shedding new light on the nature of change over solar-cycle timescales. Assuming there is no trend in temperature, at 70 • N there is evidence for a summer trend of ∼ 1.6 km decade −1 , but for winter and at 52 • N there is no significant evidence for change at all. If the temperature at 90 km is estimated using meteor trail data, it is possible to estimate a cooling rate, which, if applied to the turbopause altitude estimation, fails to alter the trend significantly irrespective of season.The observed increase in turbopause height supports a hypothesis of corresponding negative trends in atomic oxygen density, [O]. This supports independent studies of atomic oxygen density, [O], using mid-latitude time series dating from 1975, which show negative trends since 2002.

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The “wave turbopause”

Cited by 29 publications

References 36 publications

The effect of the solar rotational irradiance variation on the middle and upper atmosphere calculated by a three-dimensional chemistry-climate model

The effect of the solar rotational irradiance variation on the middle and upper atmosphere calculated by a three-dimensional chemistry-climate model

Global Dynamics of the MLT

Change in turbopause altitude at 52 and 70° N

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