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Weather comprises all the various phenomena that occur in the atmosphere of a planet. On Earth the regular events include wind, storms, rain, and snow, which
occur particularly in the troposphere or the lower part of the atmosphere.
Weather is driven by energy from the sun, with key factors being temperature, humidity, atmospheric pressure, cloud cover, wind speed, and elevation.
Weather prediction
Weather stations all around the world measure these conditions on
a continuous basis. The weather system is an inherently chaotic system.
Practically this means that meteorologists can only predict the weather a few days in the future. In fact it was through studying
weather systems that chaos theory first emerged, pioneered with the aid of early computers by Edward Lorenz. Recently, though, it has been shown that the theoretical time ahead that it is possible
to forecast is not as short as previously thought. Research suggests that problems with the formulas used in current models
remains a limiting factor in the accuracy of predictions, rather than the inherently chaotic nature of the weather. However this
still only extends the forecast time by at most a week.
Weather prediction is an area of much active research, due to the advantages that an accurate forecast of the weather would
bring. Chaos theory says that small changes in the initial conditions increase exponentially over time, until the weather is very
different from what it would have been under slightly different circumstances. Forecasters are able to increase the quality of
their predictions by calculating a number of different scenarios making small changes to the initial conditions of each. These
end results are then compared, and the most common scenario is chosen as the forecast. This also has the advantage that
forecasters have an estimate of the reliability of their forecast - if different models produce wildly incompatible results the
forecast is known to be unreliable.
List of named weather, climatic or atmospheric patterns
See also: Meteorology, climate, Cycles, severe weather, extreme weather, Groundhog Day, wind, TV Nova, Weather
forecasting; Accuweather
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