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Waves and offshore engineering
Published in P. Novak, A.I.B. Moffat, C. Nalluri, R. Narayanan, Hydraulic Structures, 2017
P. Novak, A.I.B. Moffat, C. Nalluri, R. Narayanan
There is a certain interaction between the wind and the isobar spacing as given in the meteorological charts. In meteorological practice, isobars are spaced at 4 mbar in the UK and at 3 mbar in the USA. The wind direction is parallel to the lines of isobars but is modified by friction over the water surface. The pressure distribution normal to the isobars is determined by the Coriolis force resulting from the Earth’s rotation and the centripetal force due to the curvature of the moving air masses. The resultant wind is called the gradient wind. When the isobars are parallel and straight, only the Coriolis force is important and the wind is called geostrophic wind. The equation governing the motion of the geostrophic wind at a particular point is
Air Pollution and Its Control
Published in Danny D. Reible, Fundamentals of Environmental Engineering, 2017
Geostrophic flow represents the atmospheric wind field that would result in the steady-state balance of Coriolis forces and a pressure gradient, i.e., neglecting surface friction and turbulent transport of momentum to the ground. Under these conditions, the time derivatives and the turbulent diffusion terms in Equations 6.16 are neglected and the geostrophic winds in the easterly and northerly direction are respectively, () Uxg=−gf(∂z∂y)PUyg=gf(∂z∂x)P
Atmosphere
Published in Mohammad H. Sadraey, Aircraft Performance, 2017
The Coriolis force produces a deviation in the path of wind due to the Earth’s rotation (to the right in the northern hemisphere and to the left in the southern hemisphere). The amount of deflection is greatest at the poles and decreases to zero at the equator. The amount of Coriolis deflection also increases with wind speed. At high altitude, as the wind speed increases, the deflection caused by the Coriolis force also increases. Winds in which the Coriolis force is equal to and opposite the pressure-gradient force are called geostrophic winds. Geostrophic winds flow in a straight path, with velocities proportional to the pressure-gradient force.
The geostrophic regime of rapidly rotating turbulent convection
Published in Journal of Turbulence, 2021
The geostrophic regime of rotating Rayleigh–Bénard convection is an interesting state of turbulent convective flow. It is characterised by the principal geostrophic force balance between the Coriolis force and the pressure gradient. It displays a wide variety of flow structures (cells, convective Taylor columns, plumes and geostrophic turbulence) and scaling properties of statistical quantities, like the heat transfer expressed as the Nusselt number Nu. The exploration of the geostrophic regime has started only rather recently due to the challenges faced by experimentalists and numericists alike to achieve the extremely small Ekman numbers required to decisively enter this new regime [86]. Additionally, the lower E can be the larger the range of geostrophic behaviour becomes [39], allowing the consideration of subranges based on flow structure and associated scalings.
Meteorological modeling relevant to mesoscale and regional air quality applications: a review
Published in Journal of the Air & Waste Management Association, 2020
Richard T. McNider, Arastoo Pour-Biazar
As discussed first by Blackadar (1957), the low-level jet develops overnight under conditions of clear skies and relatively light geostrophic winds, where a stable boundary layer can develop (note these are often conditions for air pollution episodes). As the nighttime boundary layer stabilizes, momentum fluxes to the surface are reduced. Thus, the layer of air above the shallow nocturnal boundary layer reduces friction and begins to accelerate. As the air accelerates, Coriolis forces turn the unbalanced winds, leading to an inertial oscillation as the layer seeks a new geostrophic balance. Thus, an evolving low-level jet is a persistent part of the nocturnal boundary layer.