STOCHASTIC WEATHER TYPE SIMULATION FOR REGIONAL CLIMATE-CHANGE IMPACTASSESSMENT

A stochastic model is developed for the synthesis of daily precipitati on by weather type analysis. Daily rainfall at two sites in southern E ngland is related to the Lamb weather types by using conditional proba bilities. Time series of circulation patterns and hence rainfall are t hen generated using a Markov representation of matrices of transition probabilities between weather types. The model reproduces key aspects of the historic rainfall regime at daily, monthly, and annual temporal resolutions. The general validity of the methodology as a means of di saggregating general circulation model predictions into finer spatial scales for water resource studies is discussed. Several limitations ar e identified of which the subjectivity introduced by the weather type classification system and the nonstationarity of the precipitation cha racteristics are the most serious.