2 Air Pressure and Wind Free Online FlashCards

What is air pressure, and how does it change with altitude?

Air pressure is the force exerted by the weight of the air above a surface. It generally decreases with altitude because less air lies overhead.

Why do weather maps adjust pressure to sea level?

Weather maps often adjust pressure to sea level so measurements from places at different elevations can be compared.

What do isobars show on a weather map?

Isobars are lines on a weather map that connect places with equal pressure.

What does the spacing of isobars indicate about wind?

Closely spaced isobars indicate a strong pressure gradient and usually stronger winds; widely spaced isobars indicate a weaker gradient and lighter winds.

What is the pressure-gradient force?

The pressure-gradient force pushes air from higher toward lower pressure. A steeper pressure gradient generally produces faster winds.

How does wind flow relative to isobars above and near the surface?

Above the layer strongly affected by surface friction, winds often flow roughly parallel to isobars. Near the surface, they angle across isobars toward lows and away from highs.

What commonly happens to air around a low-pressure center?

At a low-pressure center, surface air converges and rises. Rising air cools, which can help clouds and precipitation form.

How do winds circulate around lows and highs in each hemisphere?

In the Northern Hemisphere, winds circulate counterclockwise around lows and clockwise around highs. In the Southern Hemisphere, these directions are reversed.

How does a daytime sea breeze form?

During the day, land heats faster than water. Warm air over land rises, and cooler air from over the water moves inland as a sea breeze.

What are the three prevailing wind belts and their usual directions?

Trade winds generally blow east to west in the tropics, westerlies west to east across middle latitudes, and polar easterlies east to west near the poles. These broad patterns help transport heat and moisture.

How does the Coriolis effect deflect wind?

The Coriolis effect is the apparent deflection of moving air caused by Earth’s rotation: to the right in the Northern Hemisphere and left in the Southern Hemisphere. It is weakest at the equator and stronger toward the poles.

How does surface friction affect near-surface wind?

Friction with the ground and nearby features slows near-surface wind. The slower wind is deflected less by the Coriolis effect and crosses isobars toward low pressure.