Effect of static stability on the pattern of three-dimensional baroclinic lee wave across a meso scale elliptical barrier

2004 ◽  
Vol 90 (3-4) ◽  
pp. 139-152 ◽  
Author(s):  
S. Dutta
Keyword(s):  
Three Dimensional ◽  
Static Stability ◽  
Lee Wave ◽  
Meso Scale

scholarly journals Climatological Features of the Weakly and Very Stably Stratified Nocturnal Boundary Layers. Part I: State Variables Containing Information about Regime Occupation

2019 ◽  
Vol 76 (11) ◽  
pp. 3455-3484 ◽  
Author(s):  
Carsten Abraham ◽  
Adam H. Monahan
Keyword(s):  
Wind Speed ◽  
Turbulence Intensity ◽  
Three Dimensional ◽  
Static Stability ◽  
Wind Component ◽  
State Variables ◽  
Intermittent Turbulence ◽  
Additional Information ◽  
State Variable ◽  
Mean Wind Speed

Abstract The atmospheric nocturnal stable boundary layer (SBL) can be classified into two distinct regimes: the weakly SBL (wSBL) with sustained turbulence and the very SBL (vSBL) with weak and intermittent turbulence. A hidden Markov model (HMM) analysis of the three-dimensional state-variable space of Reynolds-averaged mean dry static stability, mean wind speed, and wind speed shear is used to classify the SBL into these two regimes at nine different tower sites, in order to study long-term regime occupation and transition statistics. Both Reynolds-averaged mean data and measures of turbulence intensity (eddy variances) are separated in a physically meaningful way. In particular, fluctuations of the vertical wind component are found to be much smaller in the vSBL than in the wSBL. HMM analyses of these data using more than two SBL regimes do not result in robust results across measurement locations. To identify which meteorological state variables carry the information about regime occupation, the HMM analyses are repeated using different state-variable subsets. Reynolds-averaged measures of turbulence intensity (such as turbulence kinetic energy) at any observed altitude hold almost the same information as the original set, without adding any additional information. In contrast, both stratification and shear depend on surface information to capture regime transitions accurately. Use of information only in the bottom 10 m of the atmosphere is sufficient for HMM analyses to capture important information about regime occupation and transition statistics. It follows that the commonly measured 10-m wind speed is potentially a good indicator of regime occupation.

Forcing of oceanic mean flows by dissipating internal tides

2012 ◽  
Vol 708 ◽  
pp. 250-278 ◽  
Author(s):  
Nicolas Grisouard ◽  
Oliver Bühler
Keyword(s):  
Numerical Study ◽  
Three Dimensional ◽  
Wave Drag ◽  
Perturbation Series ◽  
Internal Tides ◽  
Time Averaging ◽  
Mean Flow ◽  
Wave Source ◽  
Lee Waves ◽  
Lee Wave

AbstractWe present a theoretical and numerical study of the effective mean force exerted on an oceanic mean flow due to the presence of small-amplitude internal waves that are forced by the oscillatory flow of a barotropic tide over undulating topography and are also subject to dissipation. This extends the classic lee-wave drag problem of atmospheric wave–mean interaction theory to a more complicated oceanographic setting, because now the steady lee waves are replaced by oscillatory internal tides and, most importantly, because now the three-dimensional oceanic mean flow is defined by time averaging over the fast tidal cycles rather than by the zonal averaging familiar from atmospheric theory. Although the details of our computation are quite different, we recover the main action-at-a-distance result from the atmospheric setting, namely that the effective mean force that is felt by the mean flow is located in regions of wave dissipation, and not necessarily near the topographic wave source. Specifically, we derive an explicit expression for the effective mean force at leading order using a perturbation series in small wave amplitude within the framework of generalized Lagrangian-mean theory, discuss in detail the range of situations in which a strong, secularly growing mean-flow response can be expected, and then compute the effective mean force numerically in a number of idealized examples with simple topographies.

scholarly journals Orographic effects on a 3-D barotropic lee wave across a meso-scale mountain corner

2016 ◽  
Vol 2 (3) ◽  
Author(s):  
Prasanta Das ◽  
Somenath Dutta ◽  
Shyamal Kumar Mondal
Keyword(s):  
Orographic Effects ◽  
Lee Wave ◽  
Meso Scale

The piecewise constant symmetric potential vorticity vortex in geophysical flows

2008 ◽  
Vol 614 ◽  
pp. 145-172 ◽  
Author(s):  
ÁLVARO VIÚDEZ
Keyword(s):  
Potential Vorticity ◽  
Three Dimensional ◽  
Static Stability ◽  
Geophysical Flows ◽  
Radial Dependence ◽  
Radial Solutions ◽  
Finite Radius ◽  
Piecewise Constant ◽  
Order Of Magnitude ◽  
Horizontal Cylinders

The concept of piecewise constant symmetric vortex in the context of three-dimensional baroclinic balanced geophysical flows is explored. The pressure gradients generated by horizontal cylinders and spherical balls of uniform potential vorticity (PV), or uniform material invariants, are obtained either analytically or numerically, in the general case of Boussinesq and f-plane dynamics as well as under the quasi-geostrophic and semigeostrophic dynamical approximations. Based on the order of magnitude of the different terms in the PV inversion equation, approximated PV equations are deduced. In some of these cases, radial solutions are possible and the interior and exterior solutions are found analytically. In the case of non-radial dependence, exterior solutions can be found numerically. Linear, and upper and lower bound approximations to the full PV inversion equations, and their respective solutions, are also included. However, the general solution for the pressure gradient in the vortex exterior does not have spherical symmetry and remains as an important theoretical challenge. It is suggested that, in order to maintain everywhere the inertial and static stability of the balanced geophysical flows, small balls of finite radius, rather than PV singularities, could become, specially in numerical applications, useful mathematical objects.

scholarly journals Exploring atmospheric boundary layer characteristics in a severe SO<sub>2</sub> episode in the north-eastern Adriatic

2009 ◽  
Vol 9 (13) ◽  
pp. 4467-4483 ◽  
Author(s):  
M. T. Prtenjak ◽  
A. Jeričević ◽  
L. Kraljević ◽  
I. H. Bulić ◽  
T. Nitis ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Lower Troposphere ◽  
Temperature Inversion ◽  
Static Stability ◽  
Pollution Sources ◽  
Small Scale ◽  
Dynamical Structure ◽  
Atmospheric Conditions ◽  
Meteorological Model ◽  
Industrial Areas

Abstract. Stable atmospheric conditions are often connected with the occurrence of high pollution episodes especially in urban or industrial areas. In this work we investigate a severe SO2 episode observed on 3–5 February 2002 in a coastal industrial town of Rijeka, Croatia, where very high daily mean concentrations (up to 353.5 μg m−3) were measured. The episode occurred under high air pressure conditions, which were accompanied with a fog and low wind speeds. Three air quality models (50-km EMEP model, 10-km EMEP4HR model and 1-km CAMx model) were used to simulate SO2 concentrations fields and to evaluate the relative contribution of distant and local pollution sources to observed concentrations. Results suggest that the episode was caused predominately by local sources. Furthermore, using three-dimensional, higher-order turbulence closure mesoscale meteorological model (WRF), the wind regimes and thermo-dynamical structure of the lower troposphere above the greater Rijeka area (GRA) were examined in detail. Modelled atmospheric fields suggest several factors whose simultaneous acting was responsible for elevated SO2 concentrations. Established small scale wind directions supported the transport of air from nearby industrial areas with major pollution sources towards Rijeka. This transport was associated with strong, ground-based temperature inversion and correspondingly, very low mixing layer (at most up to about 140 m). Additionally, the surface winds in Rijeka were light or almost calm thus, preventing ventilation of polluted air. Finally, a vertical circulation cell formed between the mainland and a nearby island, supported the air subsidence and the increase of static stability.

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