12 Regional and Local Winds

12 Regional and Local Winds - Regional and local wind...

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Unformatted text preview: Regional and local wind systems and patterns GEOG 345 Oct 17 2006 Textbook: chapter 9 (except section on the monsoon) Winds and circulation Wind: movement of air Circulation: wind organized in closed patters Scales of motion microscale : up to a 100 meters mesoscale : up to 100 kilometers synoptic scale : up to 2000 kilometers global scale : entire Earth macroscale Fig. 9-1, p. 222 Scales of atmospheric motion eddies In general, larger scale motion patterns last longer. Chaotic motion of eddies is called turbulence . Table 9-1, p. 223 Scales of atmospheric motion Boundary layer Friction drag caused by interaction between objects or fluids moving alongside at different speeds Viscosity friction of fluid flow molecular viscosity from random movements / interactions between molecules (typical to slow, horizontal or laminar flow) eddy viscosity in turbulent motion, from whirling eddies Wind drag decreases with altitude (e.g. Ekman spiral) Mechanical turbulence: eddies created by obstruction Thermal turbulence: from surface heating and instability The atmospheric layer that is influenced by friction is the planetary boundary layer ~1000m, but varies considerably Exchange processes of heat, humidity etc. between the surface and the atmosphere take place in the boundary layer, often via turbulent processes Fig. 9-2, p. 224 Mechanical and thermal turbulence Instability causes eddies to grow larger. This results in faster moving air carried downwards -> stronger wind gusts. Fig. 9-3, p. 224 Vertical mixing a: stable atmosphere, smooth terrain b: unstable atmosphere, rough terrain Height of friction influence (boundary layer) depends on: 1. surface heating 2. wind speeds 3. surface roughness Fig. 9-4, p. 225 Downwind eddies (Mostly horizontal), mesoscale eddies on the leeward (downwind) side of islands Fig. 9-5, p. 225 Mountain wave eddies Often result in the formation of wave (often lenticular) clouds. Fig. 1, p. 227Fig....
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This note was uploaded on 04/10/2008 for the course GEOG 345 taught by Professor Csiszar during the Fall '06 term at Maryland.

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12 Regional and Local Winds - Regional and local wind...

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