Atmospheric boundary layers

Abstract

Since more than a dozen papers relating to atmospheric boundary layers are published every month, it is necessary to restrict the scope of this review. Here we address only fundamental aspects of the physics of the boundary layer and exclude research related to instrumentation, specific applied areas of boundary layer research, and interactions with larger‐scale circulations. Some aspects of the boundary layer will be treated very briefly or included only in the reference lists while other topics, which have been omitted in past reviews, will be covered in more depth. Wyngaard (1978, 1979), Paegle (1979), Zeman (1981) and Nieuwstadt (1982) recently surveyed many aspects of atmospheric boundary layer research.

Low-level jets and above canopy drainage as causes for turbulent exchange in the nocturnal boundary layer

“…When decoupling between the surface layer and air aloft occurs, the development of a LLJ is likely (Stull, 1988). According to Mahrt (1999), cooling over sloped terrain leads to a time-dependent and heightdependent horizontal pressure-gradient force that sets conditions favorable for the development of the LLJ. Remark-ably, all observed LLJ and ACDF follow the orientation of the valley and fl w downward from northwest to southeast (Figs.…”

“…Light colors denote high elevation, and dark colors low elevations. slopes in rather homogeneous terrain (Mahrt, 1999;Aubinet, 2008), while gravity waves are usually caused by topographic changes or irregularities of the canopy top (Lee et al, 1997). In complex terrain, all of these processes may occur, and a large effort has been made within projects like T-REX (T-REX stands for Terrain-induced Rotor EXperiment; Grubisic et al, 2008) and VTMX 2000 (Vertical Transport and MiXing; Doran et al, 2002) to understand the physics behind such (nocturnal) fl ws and how they influenc transport of matter and energy (Cooper et al, 2006;Pinto et al, 2006;Reinecke and Durran, 2009;Choukulkar et al, 2012).…”

“…In cases of a stably stratifie nocturnal boundary layer, turbulence is usually initialized by processes producing shear, e.g., drainage fl ws and gravity waves (Nakamura and Mahrt, 2005). This type of turbulence is referred to as intermittent turbulence or, as define by Mahrt (1999), as global intermittency. This intermittent turbulence plays a major role in estimating nocturnal exchange of, e.g., CO 2 , but there is no consensus on how to treat longer time series when intermittent turbulence occurs at times.…”

Outlook for Improved Numerical Weather Prediction Using Satellite Data with a Special Emphasis on the Hydrological Variables,

“…Recent pro-. gress in the parameterizations of the boundary layer in NWP models has been reviewed by Mahrt (1983). Here, we briefly describe these parameterizations from the point of view of improving them by using satellite derived information.…”

Prototypical examples of stratified shear flow

“…When considering environmental fiows, the results of these studies may be analogous to the atmospheric surface boundary layer under conditions of strong surface cooling where a stably stratifying heat fiux at the ground can lower turbulent production in the surface layer, Mahrt (1999). On the other hand, in the oceanic boundary layer the bottom surface is adiabatic, see Lien and Sanford (2004) for a good explanation of the differences between atmospheric and oceanic boundary layers.…”