The Speed of Two Moving Rainfall Events in Lund

The speed and direction of movement of rainfall patterns, assumed constant during any given storm, can be derived from data sets comprised of the coordinates (x, y) of a number of rainfall recording stations and the times of arrival (T) of some prominent feature of the recorded hyetographs. The result depends on the nature of the feature adopted. A measure of the significance of the result can also be derived by computing the reduction in the value of the RMS deviation of arrival times due to the assumption of a moving storm in contrast to the alternative assumption of random fluctuations about an equal arrival time. The paper also outlines a procedure for estimating the accuracy of the results based on repeated computations of the speed and direction using subsets of the data obtained by removing records of one rainfall measuring station. The procedure is demonstrated with data recorded in the city of Lund, Sweden, by a network of 12 stations for two different storms.