Invariance of the design storm in a region under a rainfall climate change at mid-latitudes

Abstract

The effect of climate change on severe storms is a topic of interest for water resources engineering and hydrometeorology. The question that arises is whether a climate change that increases the local rainfall, also implies an increase in severe storms intensity. In this paper the question is answered using statistical techniques with reference to a type of severe storm: The one that, each year, produces the annual maximum of daily rainfall. Time series of annual maximum of daily rainfall are used to calculate the design storm. The design storm is used in water resources for designing some types of hydraulic structures for flood control, or urban stormwater drainage. This research analyzes whether a climate change in the annual rainfall implies a climate change in the annual maximum of daily rainfall. Evidence is presented showing that these two types of time series have uncoupled evolution. The region of study is semi-arid, located in mid-latitudes, in central Argentina. A climate change in annual rainfall is detected at two sites. Annual rainfall has been increasing at a mean trend of 8 mm/year. However, the annual maximum of daily rainfall has shown a constant mean, at a 5% level of significance. The variance of the annual maximum of daily rainfall has remained constant. This result indicates that the design storm is invariant in a region of central Argentina where a strong climate change in annual rainfall is taking place. It also indicates that a rainfall climate change in a time scale, does not necessarily imply the existence of a similar climate change in embedded time scales.