Winds What causes winds?

Air Pressure Air pressure is the measure of the force with which air molecules push on a surface The air pressure is strongest in the Troposphere because of gravity

Wind Wind is the movement of air. Winds are caused by differences in air pressure. (Cause of Wind) Winds move from areas of high (cold air) pressure to areas of low (warm air) pressure Differences in air pressure is caused by differences in the temperature of the air- caused by unequal heating of the Earth

Why is the Earth Unequally Heated The Earth is unequally heat because it is titled on its axis. More of the sun’s direct rays hit the equator making the temperature at the equator warmer and the air less dense creating area of low pressure (L) The tilt of the Earth on its axis causes seasons on the Earth

Differences in air pressure are caused by unequal heating of the Earth. Cool air has higher air pressure so it flows underneath (sinks) the warm, less dense air. A. B. C.

Rising Air at the Equator Because the Earth is tilted on its axis, the equator receives more direct solar energy from the sun. Air at the equator is warmer than any where else on Earth . This less dense warm air rises creating areas of Low Pressure (L)

Sinking Air at the Poles At the poles, the air is colder and denser than surrounding air, so it sinks. Creating areas of high pressure (H)

Why does warm air cause areas of low pressure? Warm air causes areas of low pressure (L) because the air is less dense than the surrounding air and it rises

Why does sinking cold air cause areas of high pressure? Sinking cold air causes high pressure (H) because sinking air presses down on the air beneath it.

Coriolis Effect The apparent curving of path of winds and ocean currents due to the Earth’s Rotation Winds in the Northern Hemisphere curve east. Winds in the Southern Hemisphere curve west

Global Winds The combinations of convection cells and the Coriolis Effect produce patterns of air circulation called global winds

Local Winds Winds that blow over short distances and are caused by unequal heating of Earth’s surface within a small area.

Sea Breeze Sea Breeze – a wind that blows from an ocean or lake onto land.

Land Breeze Land Breeze – the flow of air from land to a body of water

Measuring Wind direction A wind vane measures wind direction. The name tells where the wind is coming from. i.e. – north wind blows from the north to the south.

Wind speed An anemometer measures wind speed.

Wind-chill factor The wind-chill factor is the increased cooling that a wind can bring.