Air Pressure And Wind Chapter 19 Global Winds

Air Pressure And Wind Chapter 19

Global Winds

Air temperatures on Earth are imbalanced because of uneven heating by the sun. The atmosphere acts as a giant heat-transfer system that balances out these differences.

Non-Rotating Earth Model (hypothetical model) • If Earth did not rotate and its surface was smooth and uniform one pair of convection cells • Heated air at equator would rise to the tropopause and be deflected towards the poles • Cooled air at the poles would sink to the ground and be deflected back towards the equator

Rotating Earth Model (actual model) Because the Earth rotates, is covered by both land water, and has varying terrain three pairs of convection cells

Local Winds. Caused by either topographic effects or by variations in surface composition (land water)

Flow of cool air from water to land during the day wind

Flow of cool air from land to water at night wind

Valley Breeze: Flow of warm air up the mountainside during the day Mountain Breeze: Flow of cool air down the mountainside at night

How Wind is Measured

Wind Vane: instrument for measuring wind direction • Winds are named based by the direction from which they flow • Units are written as cardinal directions (N, S, E, W) or as degrees in a circle (0 o to 360 o)

Anemometer: instrument for measuring wind speed

El Niño and La Niña

Normal Conditions: • Location = Pacific ocean, near the equator, off of the coasts of Ecuador and Peru in South America • Strong trade winds push a strong, warm Equatorial Current towards the west ending near Australia

Causes upwelling of coast cold, nutrientrich water rises supports huge food chain (anchovies)

El Niño (“the child” – occurs during Christmas every 3 -7 years) • Warm countercurrents become unusually strong. This suppresses the upwelling and makes the cold, nutrient- rich coastal waters warm. • Causes abnormal weather patterns and changes in food production in South America

• Global weather changes in some areas (localized phenomena) – rain in dry areas, drought in rainy areas, etc

La Niña • The opposite of El Niño occurs when the trade winds are stronger than normal and therefore the upwelling is increased and water is colder than normal

• Causes different abnormal global weather changes – colder winters, more rain in wet areas, drier in dry areas, etc. • Can increase hurricane activity