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African desert dust is emitted and long-range transported with multiple effects on climate, air quality, cryosphere, and ecosystems. On 21–23 February 2021, dust from a sand and dust storm in northern Africa was transported to Finland, north of 60°N. The episode was predicted 5 days in advance by the global operational SILAM forecast, and its key features were confirmed and detailed by a retrospective analysis. The scavenging of dust by snowfall and freezing rain in Finland resulted in a rare case of substantial mineral dust contamination of snow surfaces over a large area in the southern part of the country. A citizen science campaign was set up to collect contaminated snow samples prepared according to the scientists' instructions. The campaign gained wide national interest in television, radio, newspapers and social media, and dust samples were received from 525 locations in Finland, up to 64.3°N. The samples were utilised in investigating the ability of an atmospheric dispersion model to simulate the dust episode. The analysis confirmed that dust came from a wide Sahara and Sahel area from 5000 km away. Our results reveal the features of this rare event and demonstrate how deposition samples can be used to evaluate the skills and limitations of current atmospheric models in simulating transport of African dust towards northern Europe. [ABSTRACT FROM AUTHOR]

This study provides insights on the composition and variability of atmospheric aerosols over the United Arab Emirates (UAE) by analyzing the atmospheric conditions together with 14 years (2006–2019) of aerosol optical depth (AOD) retrieved from CALIPSO (Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation) satellite, and 7 years of AOD measured from the ground‐based Aerosol Robotic Network (AERONET). We found that mineral dust is the most prevailing aerosol subtype. In addition, polluted dust and polluted continental aerosols are observed mostly in the cold season. The AOD is higher in spring and summer, when the atmospheric conditions are more favorable to the occurrence of dust events. Moreover, there is another peak in winter associated with dust storms triggered by mid‐latitude baroclinic systems. In summer's daytime, extinction coefficients in excess of 0.2 km−1 are observed up to 3–4 km above the surface, as a result of the warmer and windier conditions. In the cold season and at night, the dust layers are confined to the lower atmosphere below 2 km. On a climatological time scale, we found that the AOD over the UAE has been decreasing since 2009, possibly due to the increasing trend in precipitation and changes in land use. This study highlights the large contribution of dust aerosols to the total aerosol load over the UAE and stresses on the need to account for mineral dust aerosols in climate‐air pollution related studies as well as weather and air quality forecasts. Key Points: Over the UAE, dust is the prevailing aerosol subtype, polluted dust and polluted continental aerosols are also observed mostly in winterIn summer, aerosols are observed up to 3–4 km above the surface, due to a deeper boundary layer. In winter they are confined below 2 kmAOD is higher in spring and summer and it has been decreasing since 2009 in correlation with positive precipitation trends [ABSTRACT FROM AUTHOR]

This study investigates the atmospheric dynamics of the major dust storm that occurred in June 2020 over the Sahara and during which dust clouds associated with the highest‐on‐record aerosol optical depths were transported toward the America. An anomalous atmospheric circulation pattern in the mid‐latitudes, linked to a circumglobal wavetrain, resulted in the development of a subtropical high‐pressure system to the west of the Saharan heat low. This created a pressure dipole and generated anomalously strong northeasterlies over the Sahara, which caused continuous dust emissions over 4 days. Occurring along the northern fringes of the intertropical discontinuity, the dust was transported to higher altitudes (6 km) by the strong updraft in this region. This injected the dust at the African Easterly Jet (AEJ) altitudes and favored a rapid westward long‐range transport. The AEJ was also anomalously strong, being strengthened by the anticyclonic circulation associated with the anomalous high. Plain Language Summary: Dust is an important constituent of the Earth's atmosphere, with a wide range of impacts ranging from human health to effects on climate. In June 2020, massive amounts of dust were lifted from the Sahara, the major dust source region in the world, and transported all the way into the Americas across the tropical Atlantic Ocean. This event was caused by the development of a subtropical high‐pressure system over northwest Africa which resulted in sustained strong northeasterlies over the Sahara generating continuous dust emissions for 4 days. Due to the strong low‐level convergence along the intertropical discontinuity region, the dust was lifted to roughly 5–6 km above the surface, and then transported westward by the stronger mid‐atmospheric winds (>20 m s−1). At Cape Verde and over large swaths of the Atlantic Ocean, the amount of dust suspended in the atmosphere was associated with the largest aerosol optical depths on record. Key Points: The dust storm was triggered by the development of a subtropical high off the coast of West Africa embedded in a circumglobal wavetrainThe stationary subtropical high increased the north‐south pressure gradient over the Sahara and generated sustained strong northeasterliesThe anticyclonic circulation associated with the high intensified the African Easterly Jet favoring a rapid westward transport of the dust plumes [ABSTRACT FROM AUTHOR]

This study highlights the occurrence of atmospheric rivers (ARs) over northwest Africa towards Europe, which were accompanied by intense episodes of Saharan dust transport all the way to Scandinavia, in the winter season. Using a combination of observational and reanalysis data, we investigate two extreme dusty AR events in February 2021 and assess their impact on snow melt in the Alps. The warm, moist, and dusty air mass (spatially-averaged 2-meter temperature and water vapour mixing ratio anomalies of up to 8 K and 3 g kg−1, and aerosol optical depths and dust loadings of up to 0.85 and 11 g m−2, respectively) led to a 50% and 40% decrease in snow depth and surface albedo, respectively, in less than one month during the winter season. ARs over northwest Africa show increasing trends over the past 4 decades, with 78% of AR events associated with severe dust episodes over Europe. • Extreme dust transport events from the Sahara towards Europe occurred in February 2021 derived by atmospheric rivers. • The dusty AR events led to snow darkening by dust deposition over the Alps with 40% decrease in snow albedo. • At the surface, a warming effect was observed due to increased downward-longwave radiation by up to 50 W m−2. • The combined effects induced a 50% decline in snow depth over the Alps in less than one month (6 February to 6 March). • Over the last 4 decades, 78% of ARs occurring over northwest Africa are associated with extreme dust events over Europe. [ABSTRACT FROM AUTHOR]

In June 2020, a major dust outbreak occurred in the Sahara that impacted the tropical Atlantic Ocean. In this study, the dust load and radiative forcing of the dust plumes on both the atmosphere and ocean surface is investigated by means of observations and modelling. We estimated dust loadings in excess of 8 Tg over the eastern tropical Atlantic, comparable to those observed over the desert during major Saharan dust storms. The dust induced an up to 1.1 K net warming of the ocean surface and a 1.8K warming of the air temperature (i.e., two to three times the respective climatological standard deviations), with a +14 W m−2 (∼28% of the mean value) increase in the surface net radiation flux at night. As the dust plumes extended all the way to the Caribbean, it is possible that this historical dust event helped fuel the record-breaking 2020 Atlantic hurricane season. The Saharan dust storm in June 2020 over the Atlantic Ocean heading to the Caribbean. Image Credit: NOAA. Dust is an important component of the Earth's atmosphere, with a wide range of impacts ranging from human health to effects on the ocean and climate. In fact, airborne dust aerosols modify the energy budget of the Earth's surface by interacting with the solar radiation in different ways where they absorb in the ultraviolet and longwave and reflect in the shortwave. In June 2020, massive amounts of dust were lifted from the Sahara, the major dust source region in the world, and transported all the way into the Americas across the tropical Atlantic Ocean. During this event, large dust loads, in excess of 8 Tg, covered the tropical Atlantic Ocean and induced a radiative forcing at the surface. The energy budget of the atmosphere and the ocean surface was impacted during this event resulting in a sustained warming during night and a cooling during day. The resulting effect of dust during this event was an increase in the air temperature and the sea surface temperature associated with an increase in the longwave radiation especially during night due to the re-emission of radiation towards the surface by the dust clouds. This warming may have contributed to the very active tropical storms' season in summer 2020. [Display omitted] • June 2020 Saharan dust storm associated with highest-on-record aerosol optical depths. • The estimated dust loads exceeded 8 Tg over the eastern tropical Atlantic. • The dust event caused a net warming of the ocean surface by up to 1.1 K. • Dust may have contributed to the extremely active 2020 Atlantic hurricane season. [ABSTRACT FROM AUTHOR]