4.3 Air Currents

Creates an area of High pressure Warm Air Rises Low density Creates an area of Low pressure Cold Air Sinks High density Creates an area of High pressure

Wind is the movement of air from an area of high pressure to an area of low pressure 2 types of wind are: Global wind patterns – affect all of Earth’s atmosphere and produces steady predictable winds. Local wind – affect smaller areas and change often

The amount of energy an area receives is affected by the Sun’s angle. More sunlight reaches Earth’s surface at the equator than at the poles

Global Winds Because warm air at the equator rises, it creates a low pressure area over the tropics. The cooler air over the poles sinks and creates a high pressure area.

The Three cell Model – also known as Wind Belts Scientists use a model that has three wind cells to describe the circulation patterns in Earth’s atmosphere. The three global cells in each hemisphere create northerly and southerly winds

The Three Global Wind Patterns

The Coriolis Effect The Earth’s rotation causes moving air and water to appear to move to the right in the Northern Hemisphere and the left in the Southern Hemisphere.

The Jet Stream The narrow band of high winds near the top of the troposphere that can move at speeds up to 300 km per hour and are unpredictable Flows around Earth from west to east making large loops to the north and south Influences weather as they move cold air from the poles toward the tropics and warm air from the tropics toward the poles.

Sea Breeze – Day On sunny days land heats up faster than water. The warm air over land rises and creates an area of low pressure. The cooler air over the water sinks creating an area of high pressure. The difference in temperature and pressure creates a cool wind that blows from the sea onto land

Land Breeze – Night At night the land cools more quickly than the water. The warm air over the water rises creating a low pressure area. The cooler air over land sinks and creates a high pressure area. This creates a breeze that moves from the land to the sea.