Dynamic Properties of Rainfall in Lund

The shape of a runoff hydrograph depends on the dynamic properties of the rainfall. The possible range of impact of the rainfall movement on runoff generating process can only be judged if the rainfall volocity and direction are known in statistical terms. This paper gives the statistical characteristic of the rainfall movement in the city of Lund. The probability distribution of rainfall velocities and relative frequencies of the rainfall direction are given, based on the analysis of 400 rainfall events observed in the city of Lund. A simple program for determination of the velocities and the directions of storm movement has been developed and tested. Results show that there are two main storm directions in Lund: the first, generally oriented to the East, is prevalent throughout the year except summer; the second, oriented to the North-North-East, occurs primarily during summer months. During summer rainfall velocity is lower and intensity higher than during the rest of the year. Rainfall velocity is lognormally distributed. A strong correlation between wind movement parameters at 700 mb height and storm velocity and direction was observed.