Case-Based Reasoning for Weather Prediction

Abstract

Computer-based forecasting of weather was first exper-imented in 1950 at Princeton University. Since then, there have been newer and more accurate methods to predict the incoming climate. One common practice of weather prediction is by using the general circula-tion models which are based on the laws of physics (J.M.Moran & M.D.Morgan 1986). These models are highly complex and computational intensive limiting their use for only short range predictions and that too needing supercomputers. The accuracy of fore-casting deteriorates rapidly for periods longer than 48 hours and it often becomes minimal beyond 10 days due to imperfections in the models. The analog tech-nique of weather forecasting is another approach which searches for periods in the past when the current condi-tions were similar and use the past spatial patterns as analogs (J.T.Houghton, G.J.Jenkins, & J.J.Ephraums 1990). Long term trends and recurring events guide the decisions. This is more relevant for long range pre-dictions as well as in single station predictions. The araudog method is relatively simple compared to the complex processes of development, validation, use, and maintenance of numerical models. The analog technique closely resembles the princi-ples of case-based reasoning (CBR) (Kolodner 1993; Hammond 1989). The CBR scheme attempts to iden-tify a solution by searching a historical database of solutions. Rather than performing statistical compu-tations on past records, CBR attempts to retrieve one or a few best matching cases from its casebase and modifies them to fit the current scenario. The CBR approach often results in a faster synthesis of solutions compared to rule-based reasoning or reasoning from first principles. This paper discusses the relevance of CBR in weather forecasting and outlines an indexing and eval-uation scheme for prediction. The major issue is the task of identifying a set of indices to retrieve match-ing past case records and interpret them in the current context. For weather cases, the indices are typically the observations of relevant atmospheric parameters such as cloud amount, cloud altitude, cloud water con-