A SCALING MODEL OF A STORM HYETOGRAPH

Empirical evidence suggests that statistical properties of storm rainf all at a location and within a homogeneous season have a well-structur ed dependence on storm duration. To explain this dependence, a simple scaling model for rainfall intensity within a storm was hypothesized. It was shown both analytically and empirically that such a model can e xplain reasonably well the observed statistical structure in the inter ior of storms, thus providing an efficient parametrization of storms o f varying durations and total depths. This simple scaling model is als o consistent with, and provides a theoretical basis for, the concept o f mass curves (normalized cumulative storm depth versus normalized cum ulative time since the beginning of a storm) which are extensively use d in hydrologic design. In contrast, popular stationary models of rain fall intensity are shown unable to capture the duration dependent stat istical structure of storm depths and are also inconsistent with the c oncept of mass curves.