Review of wave‐turbulence interactions in the stable atmospheric boundary layer

Abstract

Flow in a stably stratified environment is characterized by anisotropic and intermittent turbulence and wavelike motions of varying amplitudes and periods. Understanding turbulence intermittency and wave-turbulence interactions in a stably stratified flow remains a challenging issue in geosciences including planetary atmospheres and oceans. The stable atmospheric boundary layer (SABL) commonly occurs when the ground surface is cooled by longwave radiation emission such as at night over land surfaces, or even daytime over snow and ice surfaces, and when warm air is advected over cold surfaces. Intermittent turbulence intensification in the SABL impacts human activities and weather variability, yet it cannot be generated in state-of-the-art numerical forecast models. This failure is mainly due to a lack of understanding of the physical mechanisms for seemingly random turbulence generation in a stably stratified flow, in which wave-turbulence interaction is a potential mechanism for turbulence intermittency. A workshop on wave-turbulence interactions in the SABL addressed the current understanding and challenges of wave-turbulence interactions and the role of wavelike motions in contributing to anisotropic and intermittent turbulence from the perspectives of theory, observations, and numerical parameterization. There have been a number of reviews on waves, and a few on turbulence in stably stratified flows, but not much on wave-turbulence interactions. This review focuses on the nocturnal SABL; however, the discussions here on intermittent turbulence and wave-turbulence interactions in stably stratified flows underscore important issues in stably stratified geophysical dynamics in general.

Interactions among drainage flows, gravity waves and turbulence: a BLLAST case study

“…Although the agreement between surface pressure and other parameters oscillations is quite good in some cases, linear polarization equations have been not applied to these records because of the existent difficulties when trying to isolate "clean" records in a real atmosphere like the case presented here. These difficulties have also been reported in other works (Nappo, 2012;Mahrt, 2014;Sun et al, 2015b). Figure 7.…”

“…In either case, the ubiquity of GWs in the SBL over a wide variety of scales (Belušić and Mahrt, 2012), and the presence of other turbulent and non-turbulent motions makes the study of these wave-turbulence interactions very complex (Belušić and Mahrt, 2008;Mahrt, 2009). As stated in Sun et al (2015b), complete understanding of wave-turbulence interactions is an important challenge that yet remains elusive.…”

“…However, detailed analyses of the impact of GWs on surface turbulence have received little attention in the literature (Viana et al, 2009;Sun et al, 2015b). In some cases, they have been shown to be structures that are effective at generating intermittent turbulence (Einaudi and Finnigan, 1993;Smedman et al, 1995;Román-Cascón et al, 2015a), while other studies highlight the important turbulence-suppressing effect that they can cause (Viana et al, 2009).…”

“…They have been observationally analysed using different approaches (Ralph et al, 1997;Doyle and Durran, 2002;Viana et al, 2009Viana et al, , 2010Viana et al, , 2012Sun et al, 2012;Román-Cascón et al, 2015a). All these studies illustrate the difficulties in determining the origin and formation mechanisms of GWs, their importance as sources of momentum and heat transport (Sukoriansky et al, 2009;Fernando and Weil, 2010) and the necessity of their accurate parameterization in NWP models (Fritts, 2003;Kim and Hong, 2009;Belušić and Mahrt, 2012;Nappo, 2012;Sun et al, 2015b).…”

“…They can also change the vertical and horizontal gradients of scalars and consequently the turbulent fluxes observed near surface. The theoretical study of these phenomena has been demonstrated to be very complex (Stull, 1988;Sorbjan, 1989;Fernando and Weil, 2010;Mahrt, 2014;Sun et al, 2015b), and some approximations done with laboratory experiments (Hopfinger, 1987;Riley and Lelong, 2000;Ohya et al, 2008) do not include troublesome factors of the real atmosphere. Therefore, the understanding of these processes through the observational analysis of real case studies becomes very important, especially when high-quality micrometeorological data are available for this purpose.…”