Weather
Weather comprises all the various phenomena that occur in the atmosphere of a Planet. "Weather" is normally taken to mean the activity of these phenomena over short periods of time, usually no more than a few days in length. Average weather conditions over significantly longer periods is known as Climate, which is studied by climatologists for signs of Climate change.
Terrestrial weather
- Main article: Meteorology
The Earth's atmosphere is one large inter-related system so small changes to one part can have large effects in other parts, i.e., it is a chaotic system. This makes it very difficult to accurately predict short term weather changes more than a few days in advance, though weather forecasters large and small are continually working to improve this limit through the science of the study of weather: Meteorology.
Extra-terrestrial weather
Weather phenomena and systems on other planets are thought to be similar to those on Earth, but often occur on a much bigger scale. Extra-terrestrial weather systems can be extremely stable; one of the most famous landmarks in the Solar system, Jupiter's Great Red Spot is an anticyclonic storm known to have existed for at least 300 years. On other Gas giants, the lack of a surface allows the wind to reach enormous speeds: gusts of up to 400 metres per second have been measured on the planet Neptune. This has created a puzzle for planetary scientists: The weather is created by the differential action of the Sun's energy on different places and the amount of energy received by Neptune is very, very small, relative to the Earth, yet the strength and magnitude of weather phenomena on Neptune is far, far greater than on Earth. This mystery is still to be solved.Earth's weather appears to behave based on about a half-dozen latitudinal weather zones. Jupiter's banded appearance shows over a dozen such zones, while Venus appears to have no zones at all. Studying how these systems interact has been seen as helpful in understanding Earth's.