The Discourse of Character Education

Smagorinsky, Peter; Taxel, Joel

doi:10.4324/9781410613011

Cited by 41 publications

(11 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Figure 4 gives the minimum value of U * /W * ∼ 0.04. Then, taking W * ∼ 2-3 m s −1 , yields U * ∼ 10 −1 m s −1 and therefore the maximal value of smooth-surface roughness , 1992-1993, Circles Fairall et al (1996a,c) Western Pacific Ocean Grachev and Fairall (1997) Grachev et al (1997,1998) length: z 0u ∼ 10 −1 ν/U * ∼ 10 −5 m. Thus Eq. (34) with the above empirical constants is definitely applicable up to h/z 0u < 10 8 .…”

Section: Verification Of the Model (A) Field Datamentioning

confidence: 91%

See 1 more Smart Citation

The influence of large convective eddies on the surface-layer turbulence

Zilitinkevich

Hunt

Esau

et al. 2006

Q. J. R. Meteorol. Soc.

View full text Add to dashboard Cite

SUMMARYClose to the surface large coherent eddies consisting of plumes and downdraughts cause convergent winds blowing towards the plume axes, which in turn cause wind shears and generation of turbulence. This mechanism strongly enhances the convective heat/mass transfer at the surface and, in contrast to the classical formulation, implies an important role of the surface roughness. In this context we introduce the stability-dependence of the roughness length. The latter is important over very rough surfaces, when the height of the roughness elements becomes comparable with the large-eddy Monin-Obukhov length. A consistent theoretical model covering convective regimes over all types of natural surfaces, from the smooth still sea to the very rough city of Athens, is developed; it is also comprehensively validated against data from measurements at different sites and also through the convective boundary layer. Good correspondence between model results, field observations and large-eddy simulation is achieved over a wide range of surface roughness lengths and convective boundary-layer heights.

show abstract

Section: Verification Of the Model (A) Field Datamentioning

confidence: 91%

“…The former assures adequate resolution of energy-carrying fluctuations at relatively coarse meshes; the latter implies that the simplest eddy-viscosity closure for the subgrid turbulence correctly parametrizes the energy dissipation at the smallest grid-scale (see e.g. Smagorinsky 1993). …”

Section: Verification Of the Model (A) Field Datamentioning

confidence: 99%

The influence of large convective eddies on the surface-layer turbulence

Zilitinkevich

Hunt

Esau

et al. 2006

Q. J. R. Meteorol. Soc.

View full text Add to dashboard Cite

show abstract

“…for the horizontal mixing (Smagorinsky 1963) and a turbulent-kinetic-energy-based, modified Mellor-Yamada 2.5 scheme for the vertical mixing (Helfand and Labraga 1988). Horizontal diffusion is computed based on true horizontal instead of terrainfollowing gradients.…”

Section: Model and Measurement Description (A) The Mesoscale Modelmentioning

confidence: 99%

Numerical and observational case-study of a deep Adriatic bora

Gohm

Mayr

2005

Q. J. R. Meteorol. Soc.

View full text Add to dashboard Cite

SUMMARYA detailed analysis of bora winds is presented that were observed on 28 March 2002 in the north-eastern part of the Adriatic Sea. Very high-resolution numerical simulations are compared with airborne, surface, and balloon observations. The key instrument for the verification of the numerical results is an aerosol backscatter lidar on board the DLR Falcon research aircraft. The high spatial resolution of the model and of the observational dataset allows several small-scale aspects of the bora winds to be explored. The study emphasises the great impact of boundary-layer effects including convective mixing and surface friction on the structure of the bora flow.The numerical model reveals that the diurnal cycle of the planetary boundary layer causes a diurnal variation of the gravity-wave amplitude and consequently a variation in the bora strength. The downslope flow is strongest during the night-time when the impinging air mass is stably stratified and exhibits a low-level jet. The bora strength weakens during the daytime due to the evolution of a neutrally stratified convective boundary layer. Lidar observations and simulations both suggest that the observed bora winds are driven by the dynamics of orographic gravity waves. In the deep north-easterly cross-mountain flow steeply amplified but non-breaking gravity waves as well as trapped lee waves are found throughout the troposphere. Vertical separation of the boundary layer over the steep leeward terrain slope prevents the bora flow from reaching the coast. As a result, the flow is kept aloft in a series of at least three unsteady trapped lee waves before it reattaches to the surface over the sea downstream of the mountains. No clear evidence is found for the existence of low-level rotors underneath these lee waves. The ability of the model to capture the trapped waves is found to depend on the horizontal model resolution. Bora winds are identified as jets emanating from several mountain gaps. The physical mechanism for the gap flow formation is boundary-layer separation controlled by surface friction. Flow separation is more effective over the highest terrain where a broad wake forms downstream with weak winds compared to the mountain gaps where the strong bora flow eventually reattaches to the surface. The strongest gap jet belongs to the Vratnik Pass upstream of the town Senj and forms the primary shear line in the northern Adriatic with a corresponding potential-vorticity (PV) banner. The numerical model reveals several secondary orographic PV banners and embedded PV filaments. The vertical PV distribution exhibits a two-layer structure with PV anomalies at lower (higher) elevations originating from mountain gaps (isolated mountain peaks). Surface friction has a minor direct effect on PV generation but has a major indirect effect in controlling the mechanism for the generation of PV. In a simulation without surface friction the primary PV banner forms as a result of gravity-wave breaking. In the more realistic simulation, however, the primary mechanism...

show abstract

“…Mellor and Yamada 1974;Garratt 1992); in this case the vertical diffusion coefficients are dependent on the TKE field, which in this model is a prognostic variable. In the horizontal a straightforward first-order K-theory formulation is used, with the momentum diffusion coefficient (K M ) a function of the local flow deformation (following Smagorinsky 1963). In this case, the scalar diffusion coefficient is calculated using a prescribed ratio, i.e.…”

Section: Wintertime Downslope Flow Validation and Sensitivitymentioning

confidence: 99%

The dynamics of idealized katabatic flow over a moderate slope and ice shelf

Renfrew

2004

Quart J Royal Meteoro Soc

View full text Add to dashboard Cite

SUMMARYA non-hydrostatic numerical weather prediction model has been employed to simulate idealized katabatic flows over a moderate slope and adjoining ice shelf. The topography of Coats Land and the adjoining Brunt Ice Shelf, Antarctica, has been used; this is typical of much of the Antarctic coastline. The Regional Atmospheric Modeling System Version 4.3 has been adapted for simulations over compacted snow, most notably through changes to the multi-layer soil model. The simulations are initialized using clear-sky conditions and at rest. On the slope, a shallow katabatic flow develops, the winds becoming approximately steady on the slope by ∼12 h. The peak downslope winds are about 7 m s −1 at 30 m above the snow surface. The katabatic flow depth ranges from 50 to 100 m down the slope. Over the ice shelf the katabatic flow peters out, while a pool of cold air develops, primarily through sensible-heat loss into the surface and partially balancing the net radiative-heat loss to space. Near-surface and sounding data from the model simulations compare well with archetypal and typical katabatic flow observations, especially after some tuning of the model's turbulence parametrization.An analysis of the downslope flow dynamics shows the buoyancy force is generally balanced by the inertial force, except towards the foot of the slope where it is balanced by upslope forces related to gradients in the potential-temperature deficit and katabatic-layer height, caused by the pool of cold air over the ice shelf. Over time, the cooling of the ice shelf boundary layer leads to an apparent retreat of the katabatic flow from the ice shelf and some way up the slope. The dynamical analysis explains the surface climatology observed, such that the persistent katabatic winds of Coats Land rarely reach the Brunt Ice Shelf. The simulated katabatic flow moves from 'shooting' to 'tranquil' towards the foot of the slope. This transition acts to trigger a train of internal gravity waves which propagate energy upwards away from the katabatic flow jump. Previous studies have also found shooting to tranquil katabatic flow transitions, so to generalize these findings would suggest that internal gravitywave generation is ubiquitous around much of coastal Antarctica and Greenland.

show abstract

The Discourse of Character Education

Cited by 41 publications

References 0 publications

The influence of large convective eddies on the surface-layer turbulence

The influence of large convective eddies on the surface-layer turbulence

Numerical and observational case-study of a deep Adriatic bora

The dynamics of idealized katabatic flow over a moderate slope and ice shelf

Contact Info

Product

Resources

About