Wikipedia:Today's featured article/August 10, 2011

Climate models are systems of differential equations based on the basic laws of physics, fluid motion, and chemistry. Atmospheric models calculate winds, heat transfer, radiation, relative humidity, and surface hydrology at each grid point, and evaluate interactions with neighboring points.

Numerical weather prediction uses mathematical models of the atmosphere and oceans to predict the weather based on current weather conditions. A number of global and regional forecast models are run in different countries worldwide, using current weather observations relayed from radiosondes or weather satellites as inputs to the models. Mathematical models based on the same physical principles can be used to generate either short-term weather forecasts or longer-term climate predictions. Manipulating the vast datasets and performing the complex calculations necessary to modern numerical weather prediction requires some of the most powerful supercomputers in the world. Even with the increasing power of supercomputers, the forecast skill of numerical weather models only extends to about six days. Factors affecting the accuracy of numerical predictions include the density and quality of observations used as input to the forecasts, along with deficiencies in the numerical models themselves. To quantify the large amount of inherent uncertainty remaining in numerical predictions, ensemble forecasts have been used since the 1990s to help gauge the confidence in the forecast, and to obtain useful results farther into the future than otherwise possible. (more...)

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