Simultaneous and complemantary flood events and their explanation using large scale atmospheric circulation patterns

Abstract:

Highly variable intense precipitation is responsible for most of the floods in mesoscale regions. The simultaneous occurrence of floods in different medium size catchments is often the reason for large scale floods. Depending on the geographic location and the dominating weather pattern certain catchments have frequent simultaneous extremes while others behave in a complementary fashion. The purpose of this work is to investigate the simultaneous and complementary occurrence of floods in catchments using atmospheric circulation patterns (CPs). Possible flood producing patterns are identified using areal precipitation and/or unusual discharge increases. Patterns are identified using a fuzzy rule based approach based on anomalies of the 700 hPa surfaces. The rules are formed by maximizing the explained variance under the assumption of simultaneous and complementary behavior. Differences in the performance are used to decide if catchments behave in a simultaneous or a complementary fashion.