Abstract
This study identifies and characterizes the importance of the Atmospheric Rivers in the extreme precipitation episodes that strike the Iberian Peninsula and Portugal during the extended summer months (April to September) between 1950 and 2007. The extreme precipitation days are ranked taking into account a daily gridded precipitation database for the Iberian Peninsula at a 0.2o resolution. The ranking is based on the magnitude of the extreme precipitation days considering not only on the area affected above the 95th climatological percentile but also by the precipitation intensity within the anomalous area. The Atmospheric Rivers detection scheme is used for the North Atlantic Ocean basin that allows the identification of the persistent Atmospheric Rivers that impact the Iberian Peninsula for the extended summer months. It is shown, that there is a relationship between the Atmospheric Rivers and the extreme precipitation days in Portugal especially during the transition months of April, May and September. On the contrary when analysing the entire Iberia Peninsula the impact of ARs is considerably reduced. Moreover, the impacts of the Atmospheric Rivers is considerably higher for the top ranked events in Portugal but decreases when considering less intense extreme precipitation days.
Highlights
The singular location of the Iberian Peninsula (IP), along with its geographic nature make it as one of the most interesting regions for analysing the precipitation variability (Lionello, 2012)
The summer precipitation is mostly due to local factors and meso-scale convective systems that can be responsible for high rainfall rates in the eastern half of the Iberian Peninsula especially in summer months (Serrano et al, 1999; García-Herrera et al, 2005; Paredes et al, 2006)
The results found for the Iberian Peninsula domain (Figure 6A) reveal the dominance of days of extreme precipitation not associated with Atmospheric Rivers (ARs), with the 10% of the most extreme precipitation days of the ranking, the percentage of non-occurrence of AR is on the order of 70%
Summary
The singular location of the Iberian Peninsula (IP), along with its geographic nature make it as one of the most interesting regions for analysing the precipitation variability (Lionello, 2012). Following an adapted version of the methodology considered in Ramos et al (2014a), that analyzed winter extreme precipitation days, the anomalous magnitude of a summer extreme precipitation event is represented by the area of grid points above the climatological 95th percentile and the mean anomaly of that area.
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