How does the Weather Generator work?
Weather generators have been used for many years in studies of flood risk and water resources. The Weather Generator works by generating series of numbers representing the climate variables. These numbers have a random element, but they are related to each other statistically, and are governed by their overall properties (for example, the average is fixed to a particular value). The Weather Generator initially predicts daily precipitation and uses this to derive other variables, for example temperature. The statistical relationships between precipitation and other climate variables are derived from observations for a particular time of year. This method has been found to work well for a wide range of variables and conditions, can reproduce seasonality and sequences of weather, and can even reproduce the statistics of some extreme events reasonably well. For future climates, the statistics used to set up the weather generator are perturbed using change factors derived from the probabili
