Meteorological Driving Mechanisms and Human Impacts of the February 1979 Extreme Hydro-Geomorphological Event in Western Iberia

Abstract

Abstract:The large number of floods and landslides that occurred on 5-16 February 1979 in Portugal was a major hydro-geomorphologic extreme event according to the DISASTER database in terms of number of displaced people. The February 1979 event is the top ranked episode in terms of the total number of evacuated people (4244), displaced people (14,322) and also on the number of days of event duration (12 days) for the period 1865-2015. In this event, 62 damaging floods and five damaging landslides causing eight fatalities were recorded in Portugal. This event was driven by an unusually intense atmospheric forcing mechanism acting at different time scales. Despite the intense magnitude and the widespread impact on the population, this event has not been studied in detail. In this study, we show that the precipitation period of February 1979 had produced several multi-day accumulated precipitation events over the Portuguese continental territory, ranking among the top 10 events observed between 1950-2008. Additionally, most of the precipitation from this event occured in days in which atmospheric circulation was dominated by "wet" circulation weather types (CWTs), namely, cyclonic (C), west (W) or southwest (SW) types.

Assessing the Use of Satellite-Based Estimates and High-Resolution Precipitation Datasets for the Study of Extreme Precipitation Events over the Iberian Peninsula

“…It is believed that, unless an event strictly peaks during the time lag, the defined accumulation period is robust and no artificial features are found at the border between the two countries. Other studies made use of precipitation data from IB02 for real case study analysis [10,37] and for more extensive assessments [39][40][41].…”

“…Over the Iberian Peninsula (IP) an objective ranking of EPEs has been provided at daily [5] and multi-day scales [6] for the extended wintertime season (October to March), based on the high-resolution (0.2 • × 0.2 • ) ground-based precipitation dataset IB02 (further details are provided in Section 2.2). Some significant EPEs which occurred in the past have been examined both in terms of mechanisms and related impacts [7][8][9][10][11]. Given the high temporal and spatial variability of IP climatology [12,13], some studies also focus on sub-regions of the IP that are affected by specific weather regimes [14][15][16].…”

A centennial catalogue of hydro-geomorphological events and their atmospheric forcing

“…Event #95 is the most important extreme disaster event concerning evacuated and displaced people (probability ≤ 0.01 in both cases) following the general floods occurred in 1979 especially along the Tagus basin ( Rebelo et al, 2018 ). For instance, the probability of an event to generate more than 10 evacuated or displaced persons is 0.66 in both cases ( Fig.…”

“…Using this methodology, 26 different weather types are defined, where the flow is classified into eight directional CWTs, namely, northeast (NE), east (E), southeast (SE), south (S), southwest (SW), west (W), northwest (NW), north (N), and two rotational CWTs, namely, cyclonic (C) and anticyclonic (A) and 16 hybrid types (8 for each C or A hybrid). Since it is not practical to work with 26 CWT we have re-ordered them into 10 types where the 16 hybrid (8 for each C or A hybrid) CWT are assigned to their corresponding directional CWT ( Ludwig et al, 2016;Rebelo et al, 2018 ).…”

“…The previous analyses of selected individual case studies were conditioned by the available datasets or purpose of the study and were evaluated on a case-by-case approach. Some authors selected extreme events based on socioeconomic impacts ( Fragoso et al, 2012;Pereira et al, 2016;Rebelo et al, 2018;Trigo et al, 2016Trigo et al, , 2014 whereas others analysed precipitation extremes based on different selected criteria ( Fragoso et al, 2015;Liberato et al, 2013 ). Nevertheless, most of these individual events present very different large-scale atmospheric conditions in their genesis.…”