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What Drives the Weather
Notes:
Weather is very complex, but the four factors shown here are the most important drivers of the weather.
Sun and Seasons (animated): This animation shows how the sun illuminates the earth during the 4 seasons. As you can see the tilt of the earth means that both the duration and angle of the sun changes as the seasons change. This, in turn, changes the amount of heat presented to the ground, sky, and ocean.
Rotation: The rotation of the earth causes a number of effects. The earth spins faster near the equator than at the poles. The wind is subject to Conservation of Angular Momentum just as a spinning ice skater. Thus wind traveling north from the equator will be traveling faster than the ground as it moves north. This will force the wind to curve to the east (become a westerly flow). The opposite occurs for winds traveling south. In addition the Coriolis effect also introduces a curvature (relative to the earth) in any object trying to move in a straight line.
High to Low Pressure: Hot air is less dense than cold air. Thus in the absence of other forces hot air will tend to rise and cold sink. Similarly the air normally gets colder the higher you go. The earth will try to even the pressure by causing winds to flow due the pressure differences. The rotation of the earth forces the winds to circulate around the areas of high and low pressure. Instead of between them. This preserves the different regions of pressure.
Hot Transfers to Cold: Finally regardless of season the tropical regions are hotter than the polar regions. In the summer this difference is less than the winter. The laws of Thermodynamics say heat will flow from hot regions to cold.