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Local wind system

Local wind system. Sea breeze. Daytime development of sea breeze. Sea breeze. Land breeze. Nighttime development of land breeze. Land breeze. Valley / Anabatic wind. Daytime development of valley breeze found in regions with great topographic relief. Valley / Anabatic wind.

deborah-mcintosh
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Local wind system

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  1. Local wind system

  2. Sea breeze Daytime development of sea breeze

  3. Sea breeze

  4. Land breeze Nighttime development of land breeze

  5. Land breeze

  6. Valley / Anabatic wind Daytime development of valley breeze found in regions with great topographic relief

  7. Valley / Anabatic wind

  8. Valley / Anabatic wind • It develops during the day as the Sun heats the land surface and air at the valley bottom and sides. • As the air heats it becomes less dense and buoyant and begins to flow gently up the valley sides. • Vertical ascent of the air rising along the sides of the mountain is usually limited by the presence of a temperature inversion layer. • When the ascending air currents encounter the inversion they are forced to move horizontally and then back down to the valley floor. • This creates a self-contained circulation system. If conditions are right, the rising air can condense and form into cumuliform clouds.

  9. Mountain / Katabatic wind Nighttime development of mountain breeze found in regions with great topographic relief

  10. Mountain / Katabatic wind

  11. Mountain / Katabatic wind • During the night, the air along the mountain slopes begins to cool quickly because of longwave radiation loss. • As the air cools, it becomes more dense and begins to flow downslope causing a mountain breeze. • Convergence of the draining air occurs at the valley floor and forces the air to move vertically upward. • The upward movement is usually limited by the presence of a temperature inversion which forces the air to begin moving horizontally. • This horizontal movement completes the circulation cell system. In narrowing terrain, mountain winds can accelerate in speed because of the venturi effect. • Such winds can attain speeds as high has 150 kilometers per hour.

  12. Fohn Wind / the Chinook Adiabatic warming of downward moving air produces the warm Chinook wind

  13. Fohn Wind / the Chinook • Fohn wind is a warm, dry wind • blowing down on the leeward side of a mountain • facing away from the prevailing wind on the windward slope. • It is best known in the valleys of the northern Alps, • the Chinook in the eastern side of the Rockies (Canada & USA), the Nor’Wester (New Zealand) and the Samoon (Iran).

  14. Fohn Wind / the Chinook • It is characterized with higher temperature and lower relative humidity than the air on the windward slope. • When an air flow crosses over the mountain, gravity makes the air sink. • It becomes warmer as it drains lower along the slope. • Warming of the air is unfavourable for condensation as R.H. reduces. • This much drier side is also known as the rain-shadow area.

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