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What causes winds to blow?

Strong winds in CroatiaWind is air moving from one area to another. They are the result of the Sun’s uneven heating of the Earth’s surface. This is partly because the Sun's rays strike different parts of the Earth at different angles, but also because the Earth has oceansmountains and other landscape features—meaning some places warm up more quickly than others. As a result, since the temperature of the surface affects the temperature of the air above, there are pockets of warm air and cool air. When the air warms up, the air molecules move faster, spread out and rise. When the air is cooler, the molecules slow down, come together and sink. As the pockets of warm air rise, the cool air moves in to replace it. This movement of air we call the wind.

High winds cause a waterfall to go backwards{more}

Areas of high (H) and low (L) pressure in the US

Atmospheric pressure

Pressure at the Earth's surface is a measure of the weight of the air in the atmosphere pressing down on to it. The greater the mass of air above, the higher the pressure. Different places have differences in atmospheric pressure, according to whether the air is rising or sinking. Where air is rising, there is lower pressure at the Earth's surface. Where air is sinking, there is higher pressure.
Air at the surface will always move from high to low pressure to balance out the differences in pressure. The greater the difference in pressure, the faster the air will move from the high to low pressure. That rush of air we experience as the wind.

Wind direction is usually described in terms of the direction from which it originates. For example, a northerly wind blows from the north to the south.


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