Changes in seasonality and magnitude of sub-daily rainfall extremes in Emilia-Romagna (Italy) and potential influence on regional rainfall frequency estimation

Abstract

Study region: The present study focuses on Emilia-Romagna (northern Italy), a densely populated region affected in the last few years by several destructive flood events. Study focus: A rich and detailed regional dataset of annual maximum series (AMS) of sub-daily rainfall is considered with a three-fold aim: to detect possible changes in (1) seasonality and (2) magnitude of sub-daily rainfall extremes, (3) to assess the current reliability and accuracy of a previously developed regional model for rainfall frequency estimation based on the local value of mean annual precipitation (MAP). New hydrological insights for the region: The main findings of the study include: (1) delay (towards Autumn) in the mean timing of sub-daily rainfall extremes, more marked for higher elevations and longer durations; (2) significant increase in the magnitude of sub-daily extreme events for some areas, especially in the Apennine; (3) high sensitivity of the regional predictions of the frequency regime of sub-daily rainfall extremes to local changes in AMS and MAP.

Keywords

• Climate change
• Annual maximum series
• Mean annual precipitation
• Circular statistics
• Design storm