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Whiteout
A condition in which the sky is overcast and a blizzard is blowing, so that it is impossible to see any horizon or anything more than a few metres away.
Wind
The flow of air across the surface of the Earth. It is measured in terms of speed (by an anemometer) and direction (by a wind vane). (See: Beaufort scale and Windsock.)
Winds occur because of changes in air temperature and pressure.
Changes of temperature cause local winds, such as thermals and sea breezes. The global circulation of the atmosphere is also caused by differences
in temperature between the hot equator and the cold poles. As air flows from the equator to the poles, it is caught by the rotation of the Earth and its direction is changed. Winds flowing to the poles move in a northeasterly direction in the Northern Hemisphere (and so are
called southwesterly winds) and in a southeasterly direction in the Southern Hemisphere (and so are called northwesterly winds).
Return flows of air produce winds in the opposite directions. The northeasterly and southeasterly winds are called the trade winds.
Winds also occur when a low pressure region and high pressure region are close together. Air spirals down and out of a high pressure region and up and into a low pressure region. Buy’s Ballots Law uses the wind to tell where
the pressure systems are. If you stand in the Northern Hemisphere with your back to the wind, the low pressure is on your left-hand side. In the Southern Hemisphere the reverse is true.
(For types of wind see: Bora; Buster; Chinook; Doctor; Downdraught; Friagem; Haboob; Harmattan; Khamsin; Mistral; Monsoon; Northeaster, noreaster; Norther; Pampero; Santa Ana; Simoom; Sirocco; Trade winds.)
Windchill
This is the combined effect of
air temperature and wind that produces a ‘biting wind’. We are all familiar with the cooling effect of a summer breeze. The flow
of air over the skin carries away perspiration and makes the skin cooler. The same combined effect of temperature and wind in cold conditions is called windchill and it can cause people to lose heat from their skin faster than their bodies can replace it. In severe cases the effects of windchill can be life threatening. This most often happens to mountain climbers and others in exposed places during winter.
Windsock
A conical instrument used to measure wind speed and direction.
Wind vane
An instrument, often shaped like an arrow, that swivels to show wind direction.
 Windsock
Windward
The coast or flank of a mountain facing the prevailing winds. Windward coasts not only have frequent strong winds, but also, as the air is forced to rise over the land, it cools and releases its moisture as cloud and rain. As a result, windward areas usually get plentiful rain. Relief effects (see: Orographic effect) from windward areas are important to both the trade winds and the mid-latitude westerlies.
 Wind – Strong prevailing winds may make it impossible for trees to grow up straight. Trees like this are therefore a useful indicator of the exposure of a site to winds.
Windward
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