Jupiter has had the same storm raging for at least 300 years
Weather is not just an Earth thing. Jupiter's Great Red Spot, a vast anticyclone, has been spinning for at least three centuries, and even the Sun has weather of a sort, shedding its corona as the solar wind. Studying other worlds has helped scientists understand the skies over our own heads.
Weather is the condition of the atmosphere at one place and moment: temperature, humidity, cloud and stability. Climate is the long-run average of those conditions. Almost everything we experience as weather, from fog and snow to tornadoes and typhoons, happens in the troposphere, the lowest layer of air. Events in the stratosphere above can influence it, but exactly how is still poorly understood.
The root cause is uneven heating. Sunlight strikes the tropics steeply and higher latitudes at a shallow angle, spreading the same energy over more ground. That polar-tropical contrast drives the great circulation cells, named after Hadley and Ferrel, plus the polar cell and the jet stream, whose wobbles spin up mid-latitude cyclones. Earth's tilted axis changes the angle through the year, producing seasons, and slow shifts in the planet's orbit over thousands of years alter long-term climate.
Local contrasts matter too. Oceans, forests, ice sheets and cities reflect and absorb heat differently. Warm ground heats the air above it, which expands and lowers surface pressure; air then flows from high to low pressure as wind, bent sideways by Earth's rotation through the Coriolis effect. Simple set-ups like this combine into more complex patterns, from sea breezes to entire circulation cells. Air normally cools with height, but under an inversion the temperature rises instead, which can leave mountaintops warmer than valleys, trap fog and cap thunderstorms.
Because the atmosphere is chaotic, tiny changes can snowball into large effects, which is why weather is harder to predict than eclipses or tides. Surface temperatures on Earth typically swing across a range of about 40 degrees either side of zero Celsius over a year. People have tried to control the weather throughout history, and there is evidence that farming and industry have already altered weather patterns.
Source: Weather
