Weather and Climate Unit Investigative Science * If you have ever seen a tire go flat, you probably noticed the hissing sound of air escaping. If your hand was in front of the tire, you also felt air rushing out of the tire. * Air moves naturally from a region of high pressure to a region of low pressure. * Wind is air moving from a region of high pressure to a region of low pressure. * Winds are caused by differences in air pressure. * Bigger differences in air pressure cause stronger, faster winds. * A hurricane blows more than 120 km/hour. * Cold, dense air causes HIGH pressure. * Warm, less dense air causes LOW pressure. * COLD air has more molecules that are closer togethercreating higher pressure. * WARM air has more molecules moving at a faster rate, these spread out, causing lower pressure because there is more space between each molecule. * Differences in air pressure are caused by uneven heating of Earths surfaces by the sun. Therefore, ultimately, the Sun produces wind! https://www.youtube.com/watch?v=S5gsvtSLHPU https://www.youtube.com/watch?v=uBqohRu2RRk * Jet Stream * Local Winds * Global Winds * Local winds are caused by pressure differences over a small region. * These winds blow short distances, and they can blow in any direction. * Local temperature differences create wind wherever the geography variesfor example: where land meets water or where mountains meet valleys. * Global winds are part of a huge pattern of air circulation around the globe. * Global winds blow consistently from the same direction. * Global winds are produced by planet-scale differences that occur because of unequal heating of Earth at the equator and the poles.wind-patterns-of-the-three-wind-belts.html * The Equator is much warmer than the rest of the Earth. This is because the suns rays hit the equator directly. * Because it is warmer at the equator, the air above the equator has much less density (LOW Pressure). * Warm, moist air rises at the Equator, then cools and drops rain (Tropics). This is called a Hadley Cell * The large air mass then sinks over the planet at 30 o N and 30 o S. This air is very dry and most of the Earths deserts are located here. * Global Wind Patterns develop into 6 different zones. * Because the earth is rotating on itss axis, global winds curve slightly instead of flowing simply horizontally. * Because of the earth's rotation, the Coriolis force affects the direction of wind flow. * Named after Gustav-Gaspard Coriolis, the French scientist who described it mathematically in 1835, this force is what causes objects in the northern hemisphere to turn to the right and objects in the southern hemisphere to turn to the left. Because of the different Hadley Cells and the Coriolis Effect, Global Winds form 6 zones of Wind Patterns.