Climatology of Regional Flow Patterns around Basel

Summary Recently a method has been developed to classify local-scale flow patterns from the wind measurements at a dense network of stations. It was found that in the area around Basel twelve characteristic near-surface flow patterns occur. However, as the dense network of stations was running for one year only during the MISTRAL field experiment, no reliable climatology of the flow patterns can be inferred from these data. Mainly the annual cycle is not well determined from a single year of observations. As there exist several routinely operated meteorological stations with longer data records in and near the area discussed, a method was searched to identify the local flow patterns from the wind observations at these few permanent stations. A linear discriminant analysis turned out to be the best method. Based on wind data from 11 stations which were simultaneously in operation during 1990–1995, a six-year climatology of the flow patterns could be obtained and compared to synoptic weather types. Although there are relations to existing synoptic classes there is no unique correspondence between them and the flow patterns. Received February 24, 1997 Revised June 9, 1997