Major outcomes

 

Databases were made of climatological and extreme winter storms of the 20th century and beginning of 21st century (spanning from 1950 to 2008, with a resolution of 0.2 degree) in Iberia and North Atlantic sector, including impacts (precipitation and wind extremes), both using historical information and by using the reanalysis sources. This work resulted on a manuscript describing a new objective method for ranking daily precipitation events (Ramos et al. 2014).

 

STORMEx team has dedicated a substantial amount of time to the assessment of extreme events observed in the Euro-Atlantic region using various datasets and also a number of different atmospheric circulation diagnostic tools.

In recent years a number of extremely intense storms have affected western Europe. Among these “Xynthia” was one of the costliest in human lives and property damage. In Liberato et al. (2013) the synoptic evolution of Xynthia and associated impacts were evaluated. In this study, the role of the moisture transport in the development of extreme storms has also been assessed, namely for storm Xynthia, by using the lagrangian particle dispersion model FLEXPART. Storms “Gong” (Liberato 2014) and “Stephanie” (Ferreira et al. 2014) have also been evaluated.

 

Several historical storms have been analyzed, namely one of the strongest storms that struck Lisbon since the early 17th century, characterized by the first daily instrumental series obtained in Iberia – the observations made in Lisbon between 1 November 1724 and 11 January 1725 by Diogo Nunes Ribeiro (Domínguez-Castro et al. 2013).

 

Flash flooding induced by extreme precipitation events is one of the deadliest natural hazards in the Iberian Peninsula. The STORMEx team performed an assessment of the most extreme precipitation events that occurred over the last century in Portugal, which produced flash flooding, urban inundations and landslides, causing considerable infrastructure damage and human fatalities. This analysis provided an in-depth characterization of the synoptic conditions and large-scale dynamic mechanisms that promoted the events, primarily associated with low pressure systems that passed over the area. Liberato and Trigo (2014) showed that these events are usually triggered by poleward water vapour transport from the tropics and subtropics enhanced by extratropical cyclones. Recent work has shown that quite often these lows favoured large streams of (sub) tropical air across the North Atlantic – the so-called atmospheric rivers (Liberato et al. 2012). The relationship between North Atlantic atmospheric rivers, extratropical cyclones and the occurrence of heavy precipitation and flash-flood events on Iberia is also addressed (Liberato and Trigo 2014).

 

Several researchers of the team participate in an European initiative that evaluates the capacity of current detection algorithms to detect storm tracks in recently available new datasets (Neu et al. 2013). Results of this inter-comparison exercise serve to achieve in a comprehensive way a new approach to apply storm track detection to different GCM models output. This intercomparison has been performed for the Mediterranean Basin for each method for the different seasons and for extreme events. The characteristics of cyclone intensity (minimum central pressure), lifetime, propagation speed and minimum pressure tendency geostrophically adjusted to 60N have been assessed.

 

The Weather Research and Forecasting (WRF) model, a numerical weather prediction (NWP) and atmospheric simulation system designed by Microscale Meteorology (MMM) Division, National Center for Atmospheric Research’s (NCAR) for both research and operational applications was installed at UTAD. Numerical simulations of outstanding storms’ structure and intensity were performed with Mesoscale model WRF. Several tests were made to the model configuration including domain and physical parameterization schemes, followed by the sensitivity study of the storms (Ferreira et al. 2014).

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