On the short-term variability of turbulence and temperature in the winter mesosphere

Abstract

Abstract. Four mesosphere-lower thermosphere temperature and turbulence profiles were obtained in situ within ∼ 30 min and over an area of about 100 by 100 km during a sounding rocket experiment conducted on 26 January 2015 at Poker Flat Research Range in Alaska. In this paper we examine the spatial and temporal variability of mesospheric turbulence in relationship to the static stability of the background atmosphere. Using active payload attitude control, neutral density fluctuations, a tracer for turbulence, were observed with very little interference from the payload spin motion, and with high precision (< 0.01 %) at sub-meter resolution. The large-scale vertical temperature structure was very consistent between the four soundings. The mesosphere was almost isothermal, which means more stratified, between 60 and 80 km, and again between 88 and 95 km. The stratified regions adjoined quasi-adiabatic regions assumed to be well mixed. Additional evidence of vertical transport and convective activity comes from sodium densities and trimethyl aluminum trail development, respectively, which were both observed simultaneously with the in situ measurements. We found considerable kilometer-scale temperature variability with amplitudes of 20 K in the stratified region below 80 km. Several thin turbulent layers were embedded in this region, differing in width and altitude for each profile. Energy dissipation rates varied between 0.1 and 10 mW kg −1 , which is typical for the winter mesosphere. Very little turbulence was observed above 82 km, consistent with very weak small-scale gravity wave activity in the upper mesosphere during the launch night. On the other hand, above the cold and prominent mesopause at 102 km, large temperature excursions of +40 to +70 K were observed. Simultaneous wind measurements revealed extreme wind shears near 108 km, and combined with the observed temperature gradient, isolated regions of unstable Richardson numbers (0 < Ri < 0.25) were detected in the lower thermosphere. The experiment was launched into a bright auroral arc under moderately disturbed conditions (K p ∼ 5).

Assessment of the Precision of Spectral Model Turbulence Analysis Techniques Using Direct Numerical Simulation Data

“…Such simple spectral models which can provide suitable estimates for the 1D velocity spectrum E(k) or scalar spectrum E ϑ (k) as a function of energy dissipation rate at a range of wavenumbers evolved from a series of works (e.g., Driscoll & Kennedy, 1981, 1983Heisenberg, 1948;Lübken, 1992;Lübken et al, 1993;Tatarskii, 1971, and references therein). These models for example, of Driscoll and Kennedy (1985), Heisenberg (1948), andTatarskii (1971) are based on an assumed form for the spectral energy transfer rate (see e.g., Hinze, 1975, for details) and showed a good agreement with universal equilibrium range spectral data measured in the Earth atmosphere (e.g., Lehmacher et al, 2018;Lehmacher & Lübken, 1995;Lübken, 1992Lübken, , 1997Lübken et al, 1993Lübken et al, , 2002Rapp et al, 2004;Strelnikov et al, 2003Strelnikov et al, , 2013.…”

“…Based on a limited set of data Lübken (1997) and Lübken et al (1993) showed that application of these models reveals values of the derived energy dissipation rates which are close to each other. Since then mostly the model of Heisenberg (1948) has been applied by scientific community for derivation of turbulence energy dissipation rate, ɛ, based on the Lübken's spectral model technique (e.g., Blix et al, 2003;Chandra et al, 2012;Croskey et al, 2004;Das et al, 2009;Kelley et al, 2003;Lehmacher et al, 2006Lehmacher et al, , 2018Triplett et al, 2018). The main reason for that was the relative simplicity of implementation and numerical stability of the Heisenberg (1948) model.…”

“…introduced a spectral model method for derivation of turbulence energy dissipation rate, ɛ, based on a theory of spectral distribution of a scalar quantity in turbulence field (see e.g., Hinze, 1975;Obukhov, 1988;Tatarskii, 1971). This technique was successfully applied to fluctuations of neutral air density measured in the mesosphere by sounding rockets (e.g., Lehmacher et al, 2018;Lehmacher & Lübken, 1995;Lübken, 1992Lübken, , 1997Lübken et al, 1993Lübken et al, , 2002Strelnikov et al, 2003Strelnikov et al, , 2013Strelnikov et al, , 2017Strelnikov et al, , 2019Szewczyk et al, 2013) and to velocity fluctuations measured by stratospheric balloons (Haack et al, 2014;Schneider et al, 2015Schneider et al, , 2017Söder et al, 2019Söder et al, , 2021Theuerkauf et al, 2011). However, the underlying theory and therefore the ɛ-derivation technique are based on assumptions that might introduce some uncertainties, which are not quantified yet.…”

Short-Period Variation of the Activity of Atmospheric Turbulence in the MLT Region over Langfang

“…Focusing on turbopause, where ε has a value of zero, Hall et al [5,6] found an annual cycle in its position and studied its long-term pattern of variation. Lehmacher et al [7] examined the relationship between the spatiotemporal variation of the middle atmospheric turbulence and the static stability of the background atmosphere.…”