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Glossary Index

Avalanche Institute


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Also: Forced Convection, Natural Convection

Natural Convection results when air is heated near the earths surface and therefore rises. The vertical windspeeds are greater than those involved in any other type of air mass lifting. It is a localized effect and is not commonly an important factor in winter mountain weather.

One source of heating near the surface is air above warm open water. Cold air warming over warm ocean water can cause convection which effects maritime ranges such as the Cascades. Air crossing the great lakes (if they are not frozen) can result in convection which causes the large but locallized "Lake Effect" snowfalls in areas such as Buffalo, NY. Convection above the Great Salt Lake is one reason for the very large amounts of snow around Alta, UT.

Forced convection occurs when the air has motion imposed by some external force, typically winds. This can cause rapid heat transfer and snow loss and is behind phenomena such as a fohn or chinook.

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