Long-range Transport Of Mineral Dust Research Articles

Saharan, Aral-Caspian and Middle East dust travels to Finland (1980–2022)

Studies on atmospheric dust and long-range transport of mineral dust have been a focus of atmospheric science in recent years. With its wide range of direct and indirect effects, mineral dust is one of the most uncertain elements in the mechanisms of climate change, and a deeper understanding of its role is essential for understanding future processes.The aim of our research was to provide the first systematic data on the so far episodically documented northward transport mineral dust from arid-semiarid areas. So, in this paper, we present dust storm events from lower latitudes reaching the Finnish atmosphere, based on the MERRA-2 model Dust Column Mass Density data and after a multistep verification procedure using independent data source. In total, 86 long-range dust storm events were identified between 1980 and 2022, when air masses loaded with dust reached Finland. Based on backward-trajectories different sources were identified: 59 were Saharan, 22 were Aral-Caspian, and five were associated with Middle Eastern source areas. Considerable variation in inter-annual frequencies was observed among the source areas, which may be due to changes in circulation conditions and the effects of human activity (agriculture and land use changes in Aral Sea region).There is a clear maximum of dust events in spring (60%), followed by summer and autumn (where 10 of the 11 autumn episodes were from the Sahara). However, the number and proportion of scarce winter events have more than doubled since 2010 compared to the preceding 30 years, but no autumn events were registered during this period. This clear temporal variation coincides with changes in dust transport observed in other regions of Europe, driven by greater atmospheric meridionality associated with climate change and driven by reduced temperature difference between low and high latitudes due to enhanced temperature increases at Arctic regions.

Long-term profiling of aerosol light extinction, particle mass, cloud condensation nuclei, and ice-nucleating particle concentration over Dushanbe, Tajikistan, in Central Asia

Abstract. For the first time, continuous, vertically resolved long-term aerosol measurements were conducted with a state-of-the-art multiwavelength lidar over a Central Asian site. Such observations are urgently required in efforts to predict future climate and environmental conditions and to support spaceborne remote sensing (ground truth activities). The lidar observations were performed in the framework of the Central Asian Dust Experiment (CADEX) at Dushanbe, Tajikistan, from March 2015 to August 2016. An AERONET (AErosol RObotic NETwork) sun photometer was operated at the lidar field site. During the 18-month campaign, mixtures of continental aerosol pollution and mineral dust were frequently detected from ground to cirrus height level. Regional sources of dust and pollution as well as long-range transport of mineral dust mainly from Middle Eastern and the Saharan deserts determine the aerosol conditions over Tajikistan. In this study, we summarize our findings and present seasonally resolved statistics regarding aerosol layering (main aerosol layer depth, lofted layer occurrence); optical properties (aerosol and dust optical thicknesses at 500–532 nm, vertically resolved light-extinction coefficient at 532 nm); profiles of dust and non-dust mass concentrations and dust fraction; and profiles of particle parameters relevant for liquid water, mixed-phase cloud, and cirrus formation such as cloud condensation nuclei (CCN) and ice-nucleating particle (INP) concentrations. The main aerosol layer over Dushanbe typically reaches 4–5 km height in spring to autumn. Frequently lofted dust-containing aerosol layers were observed at heights from 5 to 10 km, indicating a sensitive potential of dust to influence cloud ice formation. Typical dust mass fractions were of the order of 60 %–80 %. A considerable fraction is thus anthropogenic pollution and biomass burning smoke. The highest aerosol pollution levels (in the relatively shallow winter boundary layer) occur during the winter months. The seasonal mean 500 nm AOT (aerosol optical thickness) ranges from 0.15 in winter to 0.36 in summer during the CADEX period (March 2015 to August 2016); DOTs (dust optical thicknesses) were usually below 0.2; seasonally mean particle extinction coefficients were of the order of 100–500 Mm−1 in the main aerosol layer during the summer half year and about 100–150 Mm−1 in winter but were mainly caused by anthropogenic haze. Accordingly, the highest dust mass concentrations occurred in the summer season (200–600 µg m−3) and the lowest during the winter months (20–50 µg m−3) in the main aerosol layer. In winter, the aerosol pollution mass concentrations were 20–50 µg m−3, while during the summer half year (spring to autumn), the mass concentration caused by urban haze and biomass burning smoke decreases to 10–20 µg m−3 in the lower troposphere. The CCN concentration levels are always controlled by aerosol pollution. The INP concentrations were found to be high enough in the middle and upper troposphere to significantly influence ice formation in mixed-phase and ice clouds during spring and summer seasons.

Lidar Based Separation of Polluted Dust Observed Over Warsaw (Case Study on 09 August 2013)

This paper presents preliminary results of using an extended POLIPHON method for separation of dust and non-dust aerosol backscatter coefficient, applied on a case study of 9th August 2013. That day, long-range transport of mineral dust over EARLINET-ACTRIS lidar site in Warsaw was observed with the 8-channel PollyXT-UW lidar. The dust particles were also observed by the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) on board the CALIPSO satellite. The backward trajectories calculated using the HYSPLIT model confirmed the air-mass transport from Northern Africa. Results yield possible dust separation for the mixture of dust with other aerosol types, such as pollution, marine type, etc.

Long-Range Transport of Mineral Dust to the Northeast Indian Ocean: Regional versus Remote Sources and the Implications

Abstract Synergizing satellite remote sensing data with vertical profiles of atmospheric thermodynamics and regional climate model simulations, we investigate the relative importance, transport pathways, and seasonality of contribution of dust from regional (Thar Desert and adjoining arid regions) and remote (southwest Asia and northeast Africa) sources over the northeast Indian Ocean [i.e., the Bay of Bengal (BOB)]. We show that while over the northern BOB dust from the regional sources contribute more than 50% to the total dust load during the southwest monsoon period (June–September), interestingly; the remote dust sources dominate rest of the year. On the other hand, over the southern BOB, dust transported from the remote-source regions dominate throughout the year. During June, the dry elevated layer (at altitudes between 850 and 700 hPa) of dust, transported across the Indo-Gangetic Plain to the northern BOB, arises primarily from the Thar Desert. Dust from remote sources in the far west reaches the southern BOB after traversing over and around the southern Indian Peninsula. Since dust from these distinct source regions have different mineral composition (hence optical properties) and undergo distinct changes during atmospheric transport, it is important to understand source-specific dust contribution and transport pathways to address dust–climate feedback.

Long-range transport of mineral dust observed with the Asian Dust and aerosol lidar observation Network (AD-Net)

AD-Net is an aerosol observation network using continuously operated multi-parameter lidars consists of 20 stations in East Asia. It is a “contributing network” of the WMO Global Atmosphere Watch (GAW) Program and is an Asian component of the GAW Aerosol Lidar Observation Network (GALION). The standard lidars in AD-Net are two-wavelength (1064 and 532 nm) and polarization (532 nm) lidars, but multiwavelength Raman lidars and a multiwavelength high-spectral-resolution (532 nm) and Raman (355 nm) lidar are also employed. The Mie scattering data from the AD-Net lidars are processed in near realtime (every hour) and published on the AD-Net www page in NetCDF format and graphical indications. AD-Net data are used in monitoring and various studies of Asian dust and regional air pollution. Analyses combining with chemical transport models showed that dust affecting the lower troposphere in Japan was mostly from the Gobi Desert, and dust from the Taklamakan was often transported in the free troposphere very long range. A case of Sahara dust transported through the Middle East and Central Asia was also found. Asian dust transported through polluted areas in East Asia is often internally mixed with air pollution. Results of studies using AD-Net lidars, in-situ polarization particle counters (POPCs), and sampling measurements of chemical composition are introduced.

Ice core record of dust sources in the western United States over the last 300 years

Over the past ~5000years, amplified dust generation and deposition in the American West has been linked to human activity. In recent decades, intensified rates of agriculture and livestock grazing have been correlated with greater dust production detected on seasonal to annual timescales. The combination of land use intensification and climate change (i.e. increased drought frequency) in North America highlights the importance of characterizing the sources of dust both before and after the influence of anthropogenic activity. We apply high-precision geochemical and isotopic (Sr and Nd isotopes) techniques to an ice core from the Upper Fremont Glacier (Wyoming, USA) to produce the first glacial dataset from the American West. Our Sr-Nd isotopic composition data indicates the evolving dust provenance to the Upper Fremont Glacier (UFG) from a long-range transport of mineral dust to a local source. This increasing input of dust from a local source is supported by a rise in average dust particle diameter combined with greater average dust concentration throughout the record. The greater presence of dust particles smaller than 2.5μm in the most recent samples from UFG ice core record support existing satellite and sediment core data regarding the effects of anthropogenic activity upon dust sources and pathways in the American West. Although the Sr-Nd isotope database in North America needs be expanded, our results provide a survey of windborne dust through the past 270years.

Atmospheric dry-deposition of mineral dust and anthropogenic trace metals to the Bay of Bengal

This manuscript presents a comprehensive data set on concentrations of crustal elements (Al, Ca, Fe and Mg) and trace metals (Pb, Cd, Cu, Mn, Cr, Co and Ni) in ambient aerosols studied from the marine atmospheric boundary layer (MABL) of the Bay of Bengal during the period of continental outflow (January–April). Based on cruises conducted during January'09 (winter) and March–April'06 (spring inter-monsoon), mass concentrations (ngm−3) of Pb (9–57), Cd (0.01–2.8), Cr (1–17) and Mn (4–103) in the outflow from the Indo-Gangetic Plain were higher during the winter compared to those in the spring inter-monsoon (Pb: 3.2–13.5; Cd: 0.1–1.6; Cr: 0.2–7.2 and Mn: 4.6–42.7). In contrast, Cu concentration was relatively high during the spring inter-monsoon (3.2–27.9ngm−3); whereas concentrations of Co and Ni were not significantly different (p-value>0.05) during the two seasons. In general, enrichment factors of Pb and Cd are higher (EFPb: ~225; EFCd: ~1165) over the southern Bay (south of 15°N) associated with south-east Asian outflow. A significant (p-value<0.05) linear relation of Pb, Cd and Cu with nss-SO42− reaffirms their anthropogenic origin. Another notable feature of temporal data relates to significantly higher ratios of crustal elements (Ca/Al and Fe/Al) associated with the long-range transport of mineral dust from the Thar Desert during the spring inter-monsoon. The deposition of mineral dust (0.3–6gm−2yr−1) to the Bay of Bengal is consistent with model results reported in the literature. However, the dominance of anthropogenic trace metals and their air–sea deposition must be considered in any assessment of factors that influence the marine ecosystem in the Bay of Bengal.

Analysis of long-range transport of aerosols for Portugal using 3D chemical transport model and satellite measurements

The objective of this work is to assess the contribution of long-range transport of mineral dust from North Africa to the air pollution levels in Portugal based on a combination of a modelling approach and satellite observations. The Comprehensive Air Quality Model (CAMx) was applied together with the updated Dust REgional Atmospheric Model (BSC-DREAM8b) to characterise anthropogenic and natural sources of primary aerosols as well as secondary aerosols formation. The modelling results, after their validation and bias removing process, have been used in combination with aerosol measurements provided by Ozone Monitoring Instrument (OMI), using OMAERUV Level-2 v003 product, aiming to better understand the advantages and shortcomings of both, satellite and modelling aerosol data.The data analysis is presented for Portugal for July 2006 focusing on aerosol optical depth (AOD) at 500 nm and aerosol type. Based on the modelling results, the importance of the long-range transport of mineral dust was demonstrated for the simulation days, achieving a 60% contribution to AOD levels. The mineral dust is affecting atmospheric layers up to 6 km but peak concentrations are presented at layers below 2 km. The model predicts a complex mixture of different types of aerosol for the pixels classified by OMI as “mineral dust” and “sulphates”. Although a good agreement between the model outputs and OMI observations has been found in terms of the spatial pattern and AOD correlation is about 0.48 for mineral dust, several problems were identified. The model is systematically underestimating the aerosol concentration at near ground level in comparison with the air quality monitoring stations, while OMI is in general overestimating AOD for the analysed period based on the comparison with AERONET data. Additionally, misclassification of mineral dust for some geographical locations and discontinuity in AOD values along the coastal line at water/land interface in the OMI data are discussed.

Mineral dust transport to the Sierra Nevada, California: Loading rates and potential source areas

[1] The transport and deposition of aeolian dust represents an important material input pathway for many marine and terrestrial ecosystems and may be an ecologically significant source of exogenous phosphorus (P) to alpine lakes. In order to assess the abundance and elemental composition of atmospheric mineral dust over the Sierra Nevada of California, we collected size-fractionated atmospheric particulate matter (PM) samples during July 2008 to March 2009 at a mixed conifer site located in Sequoia National Park. PM concentrations were at their highest levels during the dry season, averaging 8.8 ± 3.7 and 11.1 ± 7.5 μg m−3 for the coarse (1 μm < Da < 15 μm) and fine (Da < 1 μm) fractions, respectively, while winter months were characterized by low (<1 μg m−3) PM concentrations in both size fractions. Using Al as a diagnostic tracer for mineral aerosol, we observed a significant and uniform contribution (50–80%) from aeolian dust to the total coarse PM load, whereas submicron particles contained comparatively little crustal material (7–33%). The mass concentrations of elements (Fe, Ca, Mg, P, and V) in the coarse PM fraction were significantly correlated with Al throughout the study, and coarse PM exhibited elemental signatures that were temporally consistent and distinguishable from those of other sites. Conversely, higher elemental enrichments were observed in the fine PM fraction for Fe, V, and P, indicating a greater contribution from anthropogenic emissions to the fine particle load. Fe/Al and Fe/Ca ratios suggest a mixture of mineral dust from regional agricultural activities and long-range transport of mineral dust from Asia. Asian sources comprised 40–90% of mineral dust in July 2008 and then declined to between 10 and 30% in August and early September.

Impact of Pollutant Transport on the Air Quality of Shanghai in 2007

Pollutant transport has a significant impact on the air quality of Shanghai. To quantify this impact, we comprehensively analyze the characteristics and formation mechanisms of air pollution in Shanghai, using a data set covering five selected air quality monitoring sites and a meteorological site. We find air pollution events occur ∼10% of the year. These events are classified into three typical categories, namely the local pollution case (LP), the dust storm case (DS) and the regional transport case (RT), based on temporal variations and spatial distributions of PM10 and gaseous pollutants as well as meteorological factors and backward trajectories. The ratios of SO2/PM10, NO2/PM10 and PM2.5/PM10 are used as indicators of long-range transport of mineral dust, while CO proves to be a good tracer of regional transport of anthropogenic pollutants. In 2007, 64% of all pollution events were RT and the mean PM10 concentration reached 220 μg m-3. 17% of all pollution events were DS and the mean PM10 concentration reached 310 μg m-3. We estimate that transport contribution to PM10 abundance was within the range of 34% to 64% by comparing the anomaly of the background concentration with the urban concentration.

Aerosol concentrations observed at Mt. Haruna, Japan, in relation to long-range transport of Asian mineral dust aerosols

As a part of the effort to understand the structure of long-range transported aerosol plumes and local pollution, aerosol observations monitored the mass concentrations and number-size distributions during the period August 2006 to July 2009 near the top of Mt. Haruna (1365 m), an isolated mountain in the Kanto Plain in Japan. The mass concentrations observed at Mt. Haruna and plain sites showed a seasonal variation with a maximum in spring and summer, respectively. The spring peaks in aerosols at Mt. Haruna were probably caused by long-range transport of mineral dust and anthropogenic particles from the Asian continent. The summer peaks at the plain sites was attributed to local pollution from the Tokyo metropolitan area. Three examples of 2007 Asian dust events were investigated to show that aerosols may be dispersed in a complicated three-dimensional structure and that delayed arrivals of the dust plumes at plain sites compared to Mt. Haruna were not a rare case. Because of the boundary layer being stable at night, the dust layer was advected eastward without the vertical mixing before sunrise. This study suggests that after thermal convection activated by sunlight during daytime Asian dust transported in the free troposphere may be brought down into the atmospheric boundary layer, increasing the dust concentration there.

Size-segregated fluxes of mineral dust from a desert area of northern China by eddy covariance

Abstract. Mineral dust emission accounts for a substantial portion of particles present in the troposphere. It is emitted mostly from desert areas, mainly through intense storm episodes. The aim of this work was to quantify size-segregated fluxes of mineral dust particles emitted during storm events occurring in desert areas of northern China (Alashan desert, Inner Mongolia), known to act as one of the strongest sources of mineral dust particles in the Asian continent. Long-range transport of mineral dust emitted in this area is responsible for the high particle concentrations reached in densely populated areas, including the city of Beijing. Based on a theoretical analysis, an eddy covariance system was built to get size-segregated fluxes of mineral dust particles with optical diameters ranging between 0.26 and 7.00 µm. The system was optimised to measure fluxes under intense storm event conditions. It was tested in two sites located in the Chinese portion of the Gobi desert. During the field campaign, an intense wind erosion event, classified as a "weak dust storm", was recorded in one of them. Data obtained during this event indicate that particle number fluxes were dominated by the finer fraction, whereas in terms of mass, coarser particle accounted for the largest portion. It was found that during the storm event, ratios of size-segregated particle mass fluxes remained substantially constant and a simple parameterization of particle emission from total mass fluxes was possible. A strong correlation was also found between particle mass fluxes and the friction velocity. This relationship is extremely useful to investigate mechanisms of particle formation by wind erosion.

Long-range transport of mineral dust in the global atmosphere: impact of African dust on the environment of the southeastern United States.

Soil dust is a major constituent of airborne particles in the global atmosphere. Dust plumes frequently cover huge areas of the earth; they are one of the most prominent and commonly visible features in satellite imagery. Dust is believed to play a role in many biogeochemical processes, but the importance of dust in these processes is not well understood because of the dearth of information about the global distribution of dust and its physical, chemical, and mineralogical properties. This paper describes some features of the large-scale distribution of dust and identifies some of the geological characteristics of important source areas. The transport of dust from North Africa is presented as an example of possible long-range dust effects, and the impact of African dust on environmental processes in the western North Atlantic and the southeastern United States is assessed. Dust transported over long distances usually has a mass median diameter <10 microm. Small wind-borne soil particles show signs of extensive weathering; consequently, the physical and chemical properties of the particles will greatly depend on the weathering history in the source region and on the subsequent modifications that occur during transit in the atmosphere (typically a period of a week or more). To fully understand the role of dust in the environment and in human health, mineralogists will have to work closely with scientists in other disciplines to characterize the properties of mineral particles as an ensemble and as individual particles especially with regard to surface characteristics.

PIXE analysis of cascade impactor samples collected over the Pacific

Aerosol samples were collected on a cruise of the R/V Conrad in the Pacific Ocean. The cruise track was divided into two legs, the first one on the Peru/Ecuador shelf, the second through the equatorial and tropical Pacific to Hawaii. Sampling took place by means of two 1 l/min, ten-stage Battelle-type cascade impactors positioned on the foremast of the ship at about 20 m above the sea surface. Strict precautions were taken to avoid contamination of the samples by the ship itself. The impactor slides and back-up filters were analyzed for 25 elements by PIXE using a 2.4 MeV proton beam, produced by a compact cyclotron. In the samples, collected on leg 1, a significant anthropogenic component could be detected. Excess fine sulfur, excess fine potassium, and V, Ni, Cu and Zn in < 2 μ m particles were as high as 600, 10, 0.8, 0.2, 3 and 4 ng/m 3, respectively. On the other hand, most of the samples, collected on leg 2, were representative of clean marine air which was little influenced by continentally derived aerosols. The sulfur size distribution showed a very pronounced submicrometer mode of about 100 ng/m 3, suggesting a nearby sulfur source of marine origin. After crossing the intertropical convergence zone from south to north, concentrations of Fe and other crustal elements increased significantly. The size distributions and interelement ratios indicated that the elevated concentrations of these elements were due to long-range transport of mineral dust.