Current challenges in understanding and forecasting stable boundary layers over land and ice

Abstract

Understanding and prediction of the stable atmospheric boundary layer is challenging. Many physical processes come into play in the stable boundary layer (SBL), i.e., turbulence, radiation, land surface coupling and heterogeneity, orographic turbulent and gravity wave drag (GWD). The development of robust stable boundary-layer parameterizations for weather and climate models is difficult because of the multiplicity of processes and their complex interactions. As a result, these models suffer from biases in key variables, such as the 2-m temperature, boundary-layer depth and wind speed. This short paper briefly summarizes the state-of-the-art of SBL research, and highlights physical processes that received only limited attention so far, in particular orographically-induced GWD, longwave radiation divergence, and the land-atmosphere coupling over a snow-covered surface. Finally, a conceptual framework with relevant processes and particularly their interactions is proposed.

The nocturnal boundary layer transition from weakly to very stable. Part II: Numerical simulation with a second‐order model

“…It is affected by the surface energy budget, being therefore dependent on the quantities that control this budget, such as cloudiness and the surface thermal properties. A general review on the external controls on the internal SBL flow and its coupling state is provided by Steeneveld ().…”

“…It is affected by the surface energy budget, being therefore dependent on the quantities that control this budget, such as cloudiness and the surface thermal properties. A general review on the external controls on the internal SBL flow and its coupling state is provided by Steeneveld (2014). Baas et al (2018) used a single column model that solves first-order equations and TKE to simulate the SBL over a large range of stabilities as observed at the Cabauw tower, in the Netherlands.…”

Analyses of external and global intermittency in the logarithmic layer of Ekman flow

“…Further, the localized absence of turbulence in Ekman and channel flows bears a Analyses of external and global intermittency in Ekman flow 613 striking resemblance to the absence of turbulence on some or all scales, even close to the wall, observed in the atmosphere and termed global intermittency by Mahrt (1999). Hence, improved understanding of the dynamics of turbulence cessation and global intermittency in Ekman flow is of immediate relevance for the parameterization of turbulence in large-eddy simulations and global circulation models of the Earth's atmosphere -a pertinent challenge in modelling the planetary boundary layer (Sandu et al 2013;Steeneveld 2014). In the present work, the problem is approached from a conditional statistics perspective (cf.…”

“…Ansorge and J. P. Mellado of non-turbulent flow to a turbulent state is subject to the field of hydrodynamic instability, and there exists a well-developed conceptual framework to ascertain whether a laminar flow exposed to a density stratification can become turbulent when perturbed: Taylor-Goldstein stability analysis and the Miles-Howard theorem (Drazin & Howard 1966;Di Prima & Swinney 1981;Fernando 1991) correctly describe both the relative stability of a particular flow and its path to turbulence. A similar framework to determine whether a turbulent flow exposed to a density stratification re-laminarizes is still missing, and the analysis of turbulence in the very stable boundary layer remains challenging (Steeneveld 2014;Mahrt 2014).…”

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

“…NWP models have problems representing SBLs Steeneveld, 2014), which are related, for example, to the planetary boundary layer (PBL) evening transitions (Lapworth, 2015), minimum temperatures, low-level winds (Cuxart, 2008) and fog (Van der Velde et al, 2010;Román-Cascón et al, 2012) or air-quality (Andrén, 1990;Baklanov et al, 2009) forecasts. Among the reasons for these difficulties is the existence of the so-called submeso or submesoscale motions (Mahrt, 2009) that coexist with weak or very weak surface fluxes conditions .…”