Emerging extreme Saharan-dust events expand northward over the Atlantic and Europe prompting record-breaking PM₁₀ and PM_2.5 episodes

Abstract. Unprecedented extreme Saharan-dust (duxt) events have recently expanded northward, from subtropical NW Africa to the NE Atlantic and SW Europe, affecting the Canary Islands and mainland Spain. These six historic duxt episodes occurred 3–5 February 2020, 22–29 February 2020, 15–21 February 2021, 14–17 January 2022, 29 January–1 February 2022 and 14–20 March 2022. We analysed data of 330 Governmental Air Quality Monitoring Stations (AQMSs) of Spain, where PM₁₀ and PM_2.5 are measured with European EN-standards, and found that during duxt events PM₁₀ concentrations are underestimated due to technical limitations of some PM₁₀ monitors to properly measure extremely high concentrations. We assessed the consistency of PM₁₀ and PM_2.5 data and reconstructed 1414 PM₁₀ (1 h average) data of 48 AQMSs by using our novel duxt-r method. During duxt events, 1-hour average PM₁₀ and PM_2.5 concentrations were within the range 1000–6000 μg/m³ and 400–1200 μg/m³, respectively. The meteorological and dust modelling-reanalyses show that the intense winds leading to massive dust plumes occurred within meteorological dipoles formed by a blocking anticyclone over western Europe and a cut-off low located at the southwest, near the Canary Islands, Cape Verde or into the Sahara. These cyclones reached this region by two main paths: deviated southward from the Atlantic mid-latitudes westerly circulation by the blocking anticyclone over western Europe or deviated northward from the tropical belt. The 22–29 February 2020 event led to (24 h average) PM₁₀ and PM_2.5 within the range 600–1840 μg/m³ and 200–404 μg/m³, being the most intense dust episodes ever recorded in the Canary Islands. The 14–20 March 2022 event led to (24 h average) PM₁₀ and PM_2.5 values within the range 500–3070 μg/m³ and 100–690 μg/m³ in south-eastern, 200–1000 μg/m³ and 60–260 μg/m³ in central and 150–500 μg/m³ and 75–130 μg/m³ in northern regions of mainland Spain and to 150–430 μg/m³ and 30–80 μg/m³ in the Canary Islands, respectively, being the most intense dust episode ever recorded in mainland Spain. The analysis of the 2000–2022 PM₁₀ and PM_2.5 time series shows that these six duxt events have no precedent in Spain. All duxt events occurred during northern-hemisphere meteorological anomalies characterised by shifted to higher latitudes subtropical anticyclones, anomalous low pressures expanding beyond the tropical belt and a mid-latitudes amplified Rossby-waves undulation; these overall features resemble the anomalies of the atmospheric circulation linked to the anthropogenic global warming.