Geographical variation of extreme point rainfall

In 1979 the institute initiated a nationwide rain gauge system suitable for monitoring short, intense rain events. The system consists of approximately 50 measuring stations separated by one to 300 km, and covering a total of 43,000 square kilometres. At the present time the longest records include 16 years of data. Statistical analysis of the new data reveals a remarkable geographical variation which can be explained only partially by correlation with regional climatological variables that describe differences in physiography and microclimate. In addition to sampling errors orginating from use of limited samples for estimation at individual sites, there is a significant statistical residual that cannot be explained by a regional model. Consequently, the engineering application of rainfall data for design and analysis are being revised. The project aims at establishing guidelines for use of rain data in modelling of urban drainage systems.