Pressure and Wind Patterns of the Atmosphere Done By: Abdulrahman Al Huwaidi, Saif Al Khawaled, Osama Darweesh, Hamad Abdulwahab

Air pressure Air pressure is the force of air molecules pushing on an area. The greater the force, the higher the air pressure. Because air molecules move in all directions, air pressure pushes in all directions.

Air is related to altitude and density Air pressure and density are related. Just as air pressure decreases with altitude, so does the density of air. Air pressure decreases as you move higher in the atmosphere. Above each location on Earth is a column of air that stretches to the top of the atmosphere.

Air is related to altitude and density Air pressure and density are higher at sea level because a taller column of air pushes down. Air pressure and density are lower at a high altitude because a shorter column of air pushes down.

Pressure and air motion. Air pressure differences in the atmosphere affect air in a similar way. If the air pressure were the same at all locations, air wouldn’t move much. Because of differences in pressure, air starts to move from areas of higher pressure towards areas of lower pressure.

How a barometer works Air pressure can be measured in different ways. A barometer is any instrument that measures air pressure.

Uneven heating causes air to move Weather is the condition of Earth’s atmosphere at a particular time and space. Wind is an important part of weather. Wind is air that moves horizontally, or parallel to the ground. Over a short distance, wind moves directly from higher pressure towards lower pressure.

How wind forms Wind moves from an area of high pressure towards an area of low pressure.

How wind forms Sunlight strongly heats an area of ground. The ground heats the air. The warm air rises, and an area of low pressure forms. Sunlight heats an area of ground less strongly. The cooler, dense air sinks slowly, and an area of high pressure forms. Air moves as wind across the surface, from higher towards lower pressure.

Global Winds The distance winds travel varies. Some winds die out quickly after blowing a few meters. In contrast, global winds travel thousands of kilometers in a steady pattern. Global winds last for weeks.

What causes global winds Uneven heating between the equator and north and south poles causes global winds.

What causes global winds Sunlight is concentrated near the equator because it strikes the surface directly. Sunlight is more spread out near the poles because it strikes at a lower angle.

Earth’s rotation affects wind direction If Earth did not rotate, global winds would flow directly from the poles to the equator. The influence of Earth’s rotation is Coriolis Effect. Global winds turn as Earth turns beneath them.

Calm regions The air usually stays calm in high-pressure and low-pressure zones. Winds are light and they often change direction. The doldrums are a low-pressure zone near the equator. The horse latitudes are high-pressure zones located about 30 degrees north and 30 degrees south of the equator.

Wind belts The trade winds blow from the east, moving from the horse latitudes towards the equator. The westerliners blow from the west, moving from the horse latitudes toward the poles. The easterliners blow from the east, moving from the polar regions oward the mid- latitudes.

Jet streams flow near the top of the troposphere Jet streams usually flow in the upper troposphere from the west to the east for thousands of kilometers.

Monsoons Winds that change directions with the seasons are called monsoons.