Wind why does it happen

The air will be still one day, and the next, powerful gusts of wind can knock down trees. What is going on here? The main cause of wind is a little surprising. The gases that make up our atmosphere do interesting things as the temperatures change. When gases warm up, the atoms and molecules move faster, spread out, and rise.

When air is colder, the gases get slower and closer together. Colder air sinks. The sun warms up the air, but it does so unevenly. Because the sun hits different parts of the Earth at different angles, and because Earth has oceans, mountains, and other features, some places are warmer than others.

Because of this, we get pockets of warm air and cold air. Changes in air pressure over a specified horizontal distance cause air molecules from the region of relatively high air pressure to rush toward the area of low pressure.

Such horizontal pressure differences of all scales generate the wind we experience. The areas of high and low pressure displayed on a weather map in large part drive the usually gentle ambient wind flow we experience on a given day. The pressure differences behind this wind are only about 1 percent of the total atmospheric pressure, and these changes occur over the range of multiple states. The winds in severe storms, in contrast, are a result of much larger and more concentrated areas of horizontal pressure change.

Tornadoes are great examples. He found that the air pressure dropped by 10 percent of the total atmospheric value over the radius of the tornado. The magnitude of this air pressure change, and the very short distance over which it occurred, explains why the winds are so destructive in this phenomenon: air molecules are very quickly accelerated into the very low pressure at the center of the tornado where the water vapor contained in the air often condenses, creating the often visible "condensation funnel.

Sign up for our email newsletter. Already a subscriber? If the wind following the gust front is intense and damaging, the windstorm is known as a downburst. What is a downburst? A downburst is created by an area of significantly rain-cooled air that, after hitting ground level, spreads out in all directions producing strong winds. Unlike winds in a tornado, winds in a downburst are directed outwards from the point where it hits land or water. Dry downbursts are associated with thunderstorms with very little rain, while wet downbursts are created by thunderstorms with high amounts of rainfall.

What is a derecho? A derecho is a widespread and long-lived windstorm that is associated with a fast-moving band of severe thunderstorms. They can produce significant damage to property and pose a serious threat life, primarily by downburst winds.

To be classified as a derecho, the path length of the storm has to be at least miles long. Widths may vary from miles. Derechos are usually not associated with a cold front, but a stationary front. They occur mostly in July, but can occur at anytime during the spring and summer.

What is the jet stream? The jet stream is a fast flowing, river of air found in the atmosphere at around 12 km above the surface of the Earth just under the tropopause.

They form at the boundaries of adjacent air masses with significant differences in temperature, such as of the polar region and the warmer air to the south. Because of the effect of the Earth's rotation the streams flow west to east, propagating in a serpentine or wave-like manner at lower speeds than that of the actual wind within the flow.

What is a monsoon? A monsoon is a seasonal wind, found especially in Asia that reverses direction between summer and winter and often brings heavy rains. In the summer, a high pressure area lies over the Indian Ocean while a low exists over the Asian continent. The air masses move from the high pressure over the ocean to the low over the continent, bringing moisture-laden air to south Asia. During winter, the process is reversed and a low sits over the Indian Ocean while a high lies over the Tibetan plateau so air flows down the Himalaya and south to the ocean.

The migration of trade winds and westerlies also contributes to the monsoons. Smaller monsoons take place in equatorial Africa, northern Australia, and, to a lesser extent, in the southwestern United States.

What are the Santa Ana Winds? The Santa Ana winds are strong, extremely dry down-slope winds that originate inland and affect coastal Southern California and northern Baja California. Santa Ana winds blow mostly in autumn and winter, but can arise at other times of the year.

They can range from hot to cold, depending on the prevailing temperatures in the source regions, the Great Basin and upper Mojave Desert. The winds are known especially for the hot dry weather often the hottest of the year that they bring in the fall, and are infamous for fanning regional wildfires. For these reasons, they are sometimes known as the "devil winds" across Southern California.

What are the global wind patterns? The equator receives the Sun's direct rays. Here, air is heated and rises, leaving low pressure areas behind. Moving to about thirty degrees north and south of the equator, the warm air from the equator begins to cool and sink.

Between thirty degrees latitude and the equator, most of the cooling sinking air moves back to the equator. The rest of the air flows toward the poles. What are the trade winds? The trade winds are just air movements toward the equator.