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ASSESSMENT OF LARGE-SCALE CIRCULATION AND SOCIETAL IMPACTS OF THE HYDRO-GEOMORPHOLOGIC EVENT OCCURRED IN PORTUGAL, FEBRUARY 1979
Luis Rebelo * 1 , Alexandre M. Ramos 1 , Susana Da Silva Pereira 2 , Ricardo M. Trigo 1
1  Instituto Dom Luiz, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa
2  Centro de Estudos Geográficos, Instituto de Geografia e Ordenamento do Território, Universidade de Lisboa, Lisboa, Portugal

10.3390/CHyCle-2017-04833
Abstract:

Western Iberia is frequently struck by intense mid-latitude cyclones coming from the North Atlantic basin and often impinging extreme weather over large swaths of the Iberian Peninsula (IP). The spatial distribution and characterization of past floods and landslides with important social consequences in Portugal for the period 1865-2015 was performed within the context of the DISASTER project (Zezere et al., 2014). From this database, a major hydro-geomorphologic event was selected, the February 1979, in order to study its atmospheric forcings and to analyze its societal impacts.

The February 1979 event is a top ranked event in the DISASTER database regarding the total number of affected (18578), displaced (14322) and evacuated (4244) people in Portugal and in the Tagus basin (7677, 4816 and 2834, respectively).

Most of the days considered in this event produced daily precipitation values over or within the 90th-95th percentile of the corresponding long term daily precipitation series (available at high resolution between 1950 and 2008). Most of the event precipitation occurred in days characterized by wet Circulation Weather Types, i.e. cyclonic (C), west (W) or southwest (SW) types, which agrees with the assessment of wet days obtained by Trigo and DaCamara (2000) and Ramos et al. (2014) for the IP domain.

Also, throughout this period, the North Atlantic Ocean is crossed several times by narrow and prolonged bands of high moisture concentration, with cores above 9 g/kg, that originate near the Caribbean islands and move towards extratropical latitudes by the influence of southwestern low-level jets of medium or high intensity. These are mostly persistent Atmospheric Rivers (ARs) reaching the western IP coast and affecting most of the month of February until the 16th.

Overall, regarding the large-scale circulation, a deep low-pressure system located over the North Atlantic and reaching western IP, allowed for the frequent passage of frontal systems over the territory which was responsible for this precipitation event. In addition, local convective instabilities and strong moisture transport from the Tropical Atlantic produced an extremely intense 15-day precipitation event over western IP, that establishes as the meteorological trigger of the February 1979 Disaster event.

 

Acknowledgements: This work was financed by national funds through FCT - Portuguese Foundation for Science and Technology, I.P., under the framework of the project FORLAND Hydro-geomorphologic risk in Portugal: driving forces and application for land use planning (PTDC/ATPGEO/1660/2014). A. M. Ramos was also supported by a FCT postdoctoral grant (FCT/DFRH/ SFRH/BPD/84328/2012).

Keywords: Disaster Event; Circulation Weather Types; Atmospheric Rivers; Extreme Precipitation; Floods;
Comments on this paper
Sergio Vicente-Serrano
return period of the event
Dear authors,

thank you very much for the manuscript. I wonder if you have calculated the return period of the total precipitation magnitude during the 1979 event and if you plan to include an analysis of the flood frequency based on streamflow records of the Douro and Tejo basins.

thanks again

Sergio M. Vicente-Serrano
Luis Rebelo
Dear Sergio,

Thank you for your comment and the interest in our publication.

We did not yet computed the return period of the total precipitation. However we are planning on doing it for the final manuscript to be submitted to the Water special issue. In addition, the streamflow for the Douro and Tejo for the 1979 event will be put into a climatological and hydrological context, although some of the available streamflow series for the affected areas are relatively recent, i.e. only with circa 40 years of collected data.

Best regards,

Luis Rebelo



 
 
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