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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 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.1 Weather prediction
Weather stationA weather station is a facility with instruments and equipment to make weather observations by monitoring atmospheric conditions to study the weather. Typical weather stations have the following instruments: thermometer for measuring temperature barometers all around the world measure these conditions on a continuous basis. The weather system is an inherently chaotic systemChaos theory in mathematics and physics, deals with the behaviour of certain nonlinear dynamical systems that (under certain conditions) exhibit the phenomenon known as chaos most famously characterised by sensitivity to initial conditions (see butterfly. 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 LorenzEdward Norton Lorenz (born May 23, 1917), a research meteorologist at MIT, observed that minute variations in the initial values of variables in his primitive computer weather model (c. 1960) would result in grossly divergent weather patterns. This sensit. 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. This still only extends the forecast time by at most a week. However, scientists are continuously working to extend the length of the forecast period. In the last decade, advances in the science now allow forecasters to give a general idea of future conditions, such as whether the temperature or precipitation will average above or below normal well into the future. These types of forecasts have become increasingly more accurate.
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 exponentiallyIn mathematics, a quantity that grows exponentially is one that grows at a rate proportional to its size. Anything that grows by the same percentage every year (or every month, day, hour etc. is growing exponentially. For example, if the average number of 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.
2 List of named weather, climatic or atmospheric patterns
- Pineapple ExpressThe Pineapple Express is a Pacific Ocean weather system that brings wet tropical air from Hawaii (where farmers grow pineapples) to the American West Coast states of California, Oregon, and Washington, as well as the Canadian province of British Columbia.
- Siberian Express
- El NiņoEl Nino and La Nina are major temperature fluctuations in the tropical Pacific Ocean. They are Pacific signatures of the global ENSO phenomenon El Nino-Southern Oscillation . Their effect on climate in the southern hemisphere is profound. Their role in gl
- La Niņa
- Jet streamJet streams are fast flowing, confined air currents found in the atmosphere at around 12 km above the surface of the Earth, just under the tropopause. They form at the boundaries of adjacent air masses with significant differences in temperature, such as
- Gulf Stream
- Monsoon
- Walker circulation
- Scirocco
- Derecho
See also: Meteorology, climate, Cycles, severe weather, extreme weather, Groundhog Day, wind, TV Nova, Weather forecasting, AccuWeather, Weather lore, Convective Available Potential Energy
