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.
Highlights
Some of the most well studied exceptionally hot summers in recent years in Europe have been those of 2003 (Sch€ar et al, 2004; García- Herrera et al, 2010) and 2010 (Barriopedro et al, 2011; Dole et al, 2011)
Widespread above-average temperature anomalies were registered, and many new all-time temperature records were set at the time
Unprecedented absolute temperatures were recorded, over Portugal, where all-time records were broken in many places, including most of those standing since the 2003 mega-HW (Instituto Portugu^es do Mar e da Atmosfera, hereafter IPMA, 2018)
Summary
Some of the most well studied exceptionally hot summers in recent years in Europe have been those of 2003 (Sch€ar et al, 2004; García- Herrera et al, 2010) and 2010 (Barriopedro et al, 2011; Dole et al, 2011). There is an incomplete description of the relationship between such air masses originated in the desertic region of northwestern Africa and HW epi sodes in Iberia This is notable in climatological studies, stressing the need of a historical record of SIs to characterize coherently their effects on the Iberian Peninsula (IP). The main objectives of this work are: 1) Characterize the exceptionality of the extreme heat episodes that affected western and eastern IP in early August 2018 and late June 2019, respectively; 2) Describe the synoptic pattern and its spatio-temporal evolution during the events, with special emphasis on the occurrence of SIs, which are identified and tracked by designing an automatic algorithm; 3) Analyze the link between SIs and other Iberian HWs, as well as the long-term trends in the frequency of SIs affecting the Iberian Peninsula.
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