Wind field

To evaluate waves, first the wind field generating the waves should be selected. If the wave is to be considered jointly with a surge, a type of storm 

For some coastal locations the effects of wind waves are the dominant consideration in relation to flooding. When this is the case, special care should be taken in selecting the appropriate input characteristics for storms to obtain the maximum effects at the nuclear power plant. Under this condition a lower than maximum storm surge may result however, the overall flooding would be maximized. 

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Trajectory models require spatiaUy and temporaUy resolved wind fields, mixing-height fields, deposition parameters, and data on the spatial distribution of emissions. Lagrangian trajectory models assume that vertical wind shear and horizontal diffusion are negligible. Other limitations of trajectory and Eulerian models have been discussed (30). 

Replacement in kind - A replacement that satisfies design specifications, resuspension - Re-entrainment of particulate into a wind field for dispersion. 

A different approach which also starts from the characteristics of the emissions is able to deal with some of these difficulties. Aerosol properties can be described by means of distribution functions with respect to particle size and chemical composition. The distribution functions change with time and space as a result of various atmospheric processes, and the dynamics of the aerosol can be described mathematically by certain equations which take into account particle growth, coagulation and sedimentation (1, Chap. 10). These equations can be solved if the wind field, particle deposition velocity and rates of gas-to-particle conversion are known, to predict the properties of the aerosol downwind from emission sources. This approach is known as dispersion modeling. 

The structure of turbulence in the transition zone from a fully turbulent fluid to a nonfluid medium (often called the Prandtl layer) has been studied intensively (see, for instance, Williams and Elder, 1989). Well-known examples are the structure of the turbulent wind field above the land surface (known as the planetary boundary layer) or the mixing regime above the sediments of lakes and oceans (benthic boundary layer). The vertical variation of D(x) is schematically shown in Fig. 19.8b. Yet, in most cases it is sufficient to treat the boundary as if D(x) had the shape shown in Fig. 19.8a. 

Stohl A, Wotawa G, Seibert P, Kromp-Kolb H (1995) Interpolation errors in wind fields as a function of spatial and temporal resolution and their impact on different types of kinematic trajectories. J Appl Met 34 2149-2165... 

The processes of transport at the atmosphere-water surface border have been well studied. The transport of moisture from the surface of a water body into the atmosphere is one of the complicated physical processes of mass and energy exchange across the water-air interface (Figure 4.12). These processes are functions of many climatic parameters and, to a large extent, are regulated by eddy motions in the surface layer of the atmosphere determined by the wind field. 

Wind field characteristics Seawinds/QuickSCAT, ERS-2, Seawinds/ADEOS-2, SSM/I. Spaceborne system ERS-2 is equipped with scatterometer WS, synthetic aperture radar SAR, microwave radiometer MWR, altimeter RA, scanning radiometer ATSR, and the system GOME to measure ozone. 

Baker T. C. and Haynes K. F. (1987) Maneuvers used by flying male oriental fruit moths to relocate a sex pheromone plume in an experimentally shifted wind-field. Physiol. Entomol. 12, 263-279. 

In [50], the mean annual wind field compiled according to the data of the Russian Climatic Reference Book was used. The mean wind speeds became two to threefold higher. The maximums of the velocity and cyclonic vorticity of the wind were confined to the eastern part of the Black Sea. The almost twofold decrease in the horizontal grid step (11 km) as compared to [48] allowed one to reproduce in [50] a system of subbasin cyclonic and anticyclonic eddies quasiperiodic over the longitude it clearly dominated over the large-scale BSGC. The latter is represented in [50] only in the weaker mean annual current fields. 

The authors of [50] regarded the eddies as manifestations of Rossby waves modified by the bottom topography. The parameters of similar waves obtained from the data of altimeter observations (see Sect. 2.4), except for the period, are close to the model values. The annual wave period, which prevails in the observations, is absent in the model this is related to the forcing of the model BSGC by a constant mean annual wind field. 

An important result of the comparative analysis of the water circulation in different years and the relevant information on the wind field consists in the establishment of the possibility of appearance and, sometimes, long-term (up to 8 months) existence of anticyclonic eddies in the open sea (beyond the continental slope) and in revealing the factors that favor this phenomenon. Deep-sea anticyclones are characteristic only of the eastern basin (Fig. 3), where their appearance results from the separation of the anticyclones formed due to the RC instability at the sites with a narrow continental slope (Caucasian and Anatolian coasts and the southeastern coast of the Crimea) from the coast. The wide and gentle northwestern slope imposes a stabilizing effect on the RC. The anticyclonic eddies that found themselves over this slope owing to their formation off the southwestern coast of the Crimea or transfer from the eastern basin propagate to the southwest never entering the deep-water part of the sea. 

Recent studies [30,31] showed that the interannual vertical migrations of the main pycnocline in the central and near-shore regions of the Black Sea proceed differently, sometimes in opposite phases. In the last decades of the twentieth century, this resulted in a certain enhancement of the general cyclonic circulation of the Black Sea waters [30] and intensification of the MFZ in its western part [31], as a response to the multiannual increase in the relative vorticity of the wind field over the sea. 

The meteorological input required in the Unified EMEP model are the 3D horizontal and vertical wind fields, specific humidity, potential temperature cloud cover, and precipitation. The transferred surface 2D fields for use in the chemical transport model are surface pressure, 2 m temperature, surface flux of momentum, sensible and latent heat, and surface stress. All variables are given in 3-h interval. Table 13.1 lists the variables and their main purposes in the EMEP model. Inside the model different boundary layer parameters like the stability, eddy diffusion, and mixing height are calculated based on MOST. 

We have illustrated the need for initialization of non-hydrostatic as well as hydrostatic driving meteorological data for off-line atmospheric chemistry and transport models. The impact on the wind field from initialization is of the same magnitudes for both non-hydrostatic and hydrostatic data (i.e. less than a few dm/s), that indicates that no specific problem concerning initialization for mass conservation of non-hydrostatic data. 

Success of the Reel Down approach hinges on the stability of the system under stratospheric conditions (characterized by low pressures, but potentially large horizontal wind fields). Oscillatory motion developed in any axis of the suspended experiment cluster can compromise experimental control and thus the quality of the observations. A prototype system was constructed to test the feasibility of such a system in the stratosphere. Technical details are described in detail elsewhere [19]. 

The third level of complexity in airshed modeling involves the solution of the partial differential equations of conservation of mass. While the computational requirements for this class of models are much greater than for the box model or the plume and puff models, this approach permits the inclusion of chemical reactions, time-varying meteorological conditions, and complex source emissions patterns. However, since this model consists only of the conservation equations, variables associated with the momentum and energy equations—e.g., wind fields and the vertical temperature structure—must be treated as inputs to the model. The solution of this class of models will be examined here. 

While modeling approaches are inherently more desirable, empirical methods are presently the only approaches used. As indicated above, simulation of the atmospheric boundary layer is quite complex, requires substantial amounts of computing, and cannot currently predict with requisite accuracy. Our knowledge of turbulent diffusion, of the effects of terrain on ffow patterns, and of energy transfer processes is insufficient now to permit accurate predictions. Investigators have adopted the more reliable, but more limited, methods of interpolation and map construction to specify wind fields. Here, we discuss both approaches— numerical... 

The key aspect, then, in numerical simulation of the atmoLj.)heric boundary layer is the evaluation of the turbulent momentum fluxes in the time-averaged equations of motion (24). Considering this, we review briefly some of the more promising techniques that have been used to determine these fluxes. Our objective is not to give a full review, but rather to introduce the types of approaches which in the future may permit the solution of (23) and (24) and thus the prediction of urban wind fields. 

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