Applications of the transilient turbulence parameterization to atmospheric boundary-layer simulations

Abstract

An improved first-order closure approximation is developed for the non-local 'transilient turbulence' parameterization. Instead of using Richardson numbers, this improved approach uses non-local approximations to the shear, buoyancy, storage, and dissipation terms of the turbulence kinetic energy equation to parameterize the turbulent mixing potential between every combination of grid points in a I-D model of the atmosphere. The original .(n* -n) degrees of freedom associated with the independent transihent matrix coefficients for a model of n grid points is thus reduced to four degrees of freedom associated with the four free p~~eters.The resulting parameterization is applied to three consecutive case-study days of boundary-layer data acquired near the Cabauw tower in The Netherlands. The tirst day is used for sensitivity tests to select the best values of the four free parameters. The remaining two days, used as independent tests, demonstrate that realistic entraining mixed layers and nocturnal boundary layers form in the model without expiici~y paramete~2ing such boundary layers. Sim~ations are also presented for two idealized cases: 'dry' stratocumulus-induced convection and a neutral boundary layer.

Methods for determining the height of the atmospheric boundary layer

“…Stull and Driedonks (1987) ' f m erred the depth of the ABL from the height at which a rising parcel of surface layer air first becomes neutrally buoyant. Beljaars and Betts (1992) also used a lifting parcel method which includes the calculation of an excess eddy temperature at the surface from temperature profiles, u*, and the sensible surface heat flux.…”

Meteorological profiling of the lower troposphere using the research UAV "M<sup>2</sup>AV Carolo"

“…An advantage of its electric propulsion system compared to combustion engines is that the engine power is not influenced by changes in altitude and that the total weight and the centre of mass are constant during flight. This allows for a more precise measurement and calibration of the angle of attack (van den Kroonenberg et al, 2008). Compared to combustion engines, also the vibrations during flight are much weaker, resulting in a higher precision of meteorological measurements.…”

“…This allows for measurement flights in the lower ABL over larger distances outside the range of sight and in remote areas. Thereby, the M 2 AV follows the flight pattern which was sent to the aircraft before take-off (van den Kroonenberg et al, 2008). Within the telemetry range of 5 km the ground staff is able to follow and monitor the position, attitude and speed of the aircraft.…”

“…The sensor dome is mounted at the nose of the aircraft to minimize the aircraft's influence on the measurements and to get the sensors positioned close to each other. Also part of the meteorological payload is an IMU and a three-dimensional GPS system measuring and saving information about precise time, aircraft position, attitude and speed (van den Kroonenberg et al, 2008).…”

Nonlocal-Closure Schemes for Use in Air Quality and Environmental Models

“…In order to quantify the transport of a passive tracer field in three-dimensional simulations of turbulent convection, the nonlocal and non-diffusive behavior can be described by a transilient matrix whose elements contain the fractional tracer concentrations moving from one subvolume to another as a function of time. The approach was originally developed for and applied to geophysical flows known as turbulent transilient theory (T3) (Stull, 1988;Stull & Driedonks, 1987;Alapaty et al, 1997), but this formalism was extended and applied in an astrophysical context to three-dimensional simulations of turbulent compressible convection with overshoot into convectively stable bounding regions (Miesch et al, 2000). The most frequently used nonlocal-closure method is the asymmetric convective model (ACM) suggested by Pleim & Chang (1992).…”