Wind
PHYSICAL GEOGRAPHY 101

Wind

Wind is air motion with respect to the Earth's surface.
Wind typically refers to horizontal air movement.
Updrafts and downdrafts are term typically applied to vertical air movement.
Wind is the result of differences in pressure in different location - pressure gradient
Air moves from high pressure to low pressure.
It will continue to move until the pressures are equal.
The greater the pressure gradient (i.e. the greater the difference between to location's pressure) the greater the force of wind.

Causes of Unequal Pressure on the Earth's Surface

Differences in pressures over the surface of the Earth are primarily caused by uneven heating of the surface by the Sun.
Coastal areas show this process with the development of sea-breezes.

During the day, the land is heated by the sun, which in turn heats the air above the surface.
This air becomes less dense and begins to rise.
A low pressure area is created.
The air over the water stays cooler due to the thermal properties of water which distribute the solar radiation more efficiently.
The cooler air forms a high pressure area.
Air moves from high to low pressure, creating a cool breeze which moves onshore.

At night, the land cools more rapidly than the ocean, thus creating a high pressure area over the land.
Water which retains its heat longer than land keeps the air above the water warm, creating a low pressure area.
The breeze which develops moves offshore.

Wind Measurement

Two measurements are needed to characterize air movement.
Wind Direction
Wind Speed

Coriolis Effect

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