Abstract
Abstract. The yearly exceedance probability of extreme precipitation of multiple durations is crucial for infrastructure design, risk management, and policymaking. Local extremes emerge from the interaction of weather systems with local terrain features such as coastlines and orography; however, multi-duration extremes do not follow exactly the patterns of cumulative precipitation and are still not well understood. High-resolution information from weather radars could help us quantify their patterns better, but traditional extreme value analyses based on radar records were found to be too inaccurate for quantifying the extreme intensities required for impact studies. Here, we propose a novel methodology for extreme precipitation frequency analysis based on relatively short weather radar records, and we use it to investigate the coastal and orographic effects on extreme precipitation of durations between 10 min and 24 h. Combining 11 years of radar data with 10 min rain gauge data in the southeastern Mediterranean, we obtain estimates of the once in 100 years precipitation intensities with ∼26 % standard error, which is lower than those obtained using traditional approaches on rain gauge data. We identify the following three distinct regimes which respond differently to coastal and orographic forcing: short durations (∼10 min), related to peak convective rain rates, hourly durations (∼1 h), related to the yield of individual convective cells, and long durations (∼6–24 h), related to the accumulation of multiple convective cells and to stratiform processes. At short and hourly durations, extreme return levels peak at the coastline, while at longer durations they peak corresponding to the orographic barriers. The distributions tail heaviness is rather uniform above the sea and rapidly changes in presence of orography, with opposing directions at short (decreasing tail heaviness, with a peak at hourly durations) and long (increasing) durations. These distinct effects suggest that short-scale hazards, such as urban pluvial floods, could be more of concern for the coastal regions, while longer-scale hazards, such as flash floods, could be more relevant in mountainous areas.
Highlights
Knowledge of the yearly exceedance probability of extreme precipitation intensities at multiple spatiotemporal scales is crucial for infrastructure design, weather risk management, and policymaking (Chow et al, 1988; Kleindorfer and Kunreuther, 1999)
Extreme return levels are computed using simplified metastatistical extreme value (SMEV) (Marra et al, 2019b, 2020). This approach is well suited for our study case because it is less sensitive than traditional extreme value approaches (i) to measurement errors typical of radar estimates (Marra et al, 2018), (ii) to the use of short records (Zorzetto et al, 2016; Marra et al, 2018; Hu et al, 2020), and because (iii) it correctly represents the tail of sub-daily precipitation intensities (Marra et al, 2020; Wang et al, 2020)
We propose and test a novel methodology for extreme precipitation frequency analysis that allows us to adjust relatively short archives of weather radar precipitation estimates using rain gauges as a reference
Summary
Knowledge of the yearly exceedance probability of extreme precipitation intensities at multiple spatiotemporal scales is crucial for infrastructure design, weather risk management, and policymaking (Chow et al, 1988; Kleindorfer and Kunreuther, 1999). The 100-year return levels are intensities characterized by 1 % yearly exceedance probability and, exceeded on average once in 100 years (Katz et al, 2002). This task usually requires specific approaches to decrease the stochastic uncertainties characterizing the observation of extremes (e.g., Koutsoyiannis et al, 1988; Buishand, 1991; Burlando and Rosso, 1996) and simplified conceptual models to account for the multiple spatiotemporal scales required by many impact studies (Sivapalan and Bloeschl, 1998; Svensson and Jones, 2010). Mountains constrain the flow of air masses in-
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
