| مستخلص: |
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 PM2.5 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 PM2.5 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 PM2.5 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 PM2.5 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 PM2.5 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 PM2.5 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. [ABSTRACT FROM AUTHOR] |
