Publication: Saharan air intrusions as a relevant mechanism for Iberian heatwaves: the record breaking events of August 2018 and June 2019
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Publication Date
2019-12
Authors
Sousa, Pedro M.
Ramos, Alexander M.
García Herrera, Ricardo
Espírito-Santo, Fátima
Trigo, Ricardo M.
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Elsevier
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Abstract
The summers of 2018 and 2019 were characterized by unusually warm conditions over Europe. Here, we describe the intense heatwaves striking the Iberian Peninsula in early August 2018 and late June 2019. The 2018 episode was relatively short-lived but outstanding in amplitude, particularly in western Iberia. Similar to previous mega-heatwaves, the 2019 event was long-lasting and affected large areas of western and central Europe, including eastern Iberia. During these events, many absolute temperature records were broken in western and eastern Iberia, respectively (some of them standing since 2003). In both cases, a cyclonic circulation off the coast in the northeastern Atlantic and a strong subtropical ridge pattern over the affected area promoted the advection of an anomalously warm air mass. This paper highlights the role of these very warm, stable and dry air intrusions of Saharan origin in the western and eastern Iberia heatwave events. Using a thermodynamical classification based on the geopotential height thickness and potential temperature, we show how the magnitude and poleward extension of these Saharan intrusions were unprecedented in the period since 1948. The relationship between Iberian heatwaves and Saharan warm air intrusions is discussed in the long-term context, showing a closer link in southern sectors of the Peninsula. However, a consistent poleward trend in the latitudinal extension of these subtropical intrusions reveals their increasing relevance for heatwaves in northern sectors of Iberia and western Europe. This overall trend is accompanied by an apparent “see-saw” in the occurrence of subtropical intrusions between eastern and western Iberia on multi-decadal scales.
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© 2019 The Authors. We acknowledge the E-OBS dataset from the EU-FP6 project ENSEMBLES (http://ensembles-eu.metoffice.com) and the data providers in the ECA&D project (http://www.ecad.eu). PMS was supported by project IMDROFLOOD [Improving Drought and Flood Early Warning, Forecasting and Mitigation using real-time hydroclimatic indicators (WaterJPI/0004/2014)] and project HOLMDRIVE [North Atlantic Atmospheric Patterns influence on Western Iberia Climate: From the Lateglacial to the Present (PTDC/CTA-GEO/29029/2017)] through Fundação para a Ciência e a Tecnologia, Portugal (FCT). RMT was partially supported by national funds through Fundação para a Ciência e a Tecnologia, Portugal (FCT) under project FireCast (PCIF/GRF/0204/ 2017). This work was partially funded by project INDECIS, which is part of ERA4CS, an ERA-NET initiated by JPI Climate, with co-funding by the European Union (Grant 690462). AMR was supported by the Scientific Employment Stimulus 2017 from FCT (CEECIND/00027/2017). We thank the Editor and reviewers for their helpful comments on this manuscript.