A single scaling parameter to describe the rainfall pattern of a place: application on Catalonia

What is it about?

As well as in other natural processes, it has been frequently observed that the phenomenon arising from the rainfall generation process presents fractal self-similarity of statistical type, and thus, rainfall series generally show scaling properties. Based on this fact, there is a methodology, simple scaling, which is used quite broadly to find or reproduce the intensity–duration–frequency curves of a place. In the present work, the relationship of the simple scaling parameter with the characteristic rainfall pattern of the area of study has been investigated. The calculation of this scaling parameter has been performed from 147 daily rainfall selected series covering the temporal period between 1883 and 2016 over the Catalonian territory (Spain) and its nearby surroundings, and a discussion about the relationship between the scaling parameter spatial distribution and rainfall pattern, as well as about trends of this scaling parameter over the past decades possibly due to climate change, has been presented.

Featured Image

Photo by MItodru Ghosh on Unsplash

Photo by MItodru Ghosh on Unsplash

Why is it important?

Despite the general concordance between the spatial distribution of the simple scaling parameter over Catalonia and the mean annual precipitation distribution, with high values in rainy areas and low for the dry ones, some discrepancies related to the kind of precipitation contributing to high rainfall events and the proportion of convective rainfall in total appeared. The parameter values have been found to be higher as higher the percentage of annual precipitation amount that occurs during the maximum rainfall day is. Since the contribution of the maximum rainfall day to the total amount is related with rainfall irregularity, the simple scaling parameter can be also considered as an index for rainfall irregularity. Moreover, the analysis of the temporal evolution of the simple scaling parameter during the 20th century in Catalonia has shown a slight decreasing trend over the past century and the beginning of the current one. This result is compatible with the expected trend of decrease in annual precipitation and relative increase in extreme rainfall in many areas of Europe projected by several regional climate models for the 21st century.