AS3.10

The Joint Aeolus Tropical Atlantic Campaign (JATAC) has been conducted in summer/autumn 2021 at the Cape Verde, with the main aim to provide reference measurements for the validation of the Aeolus products and to collect information for ESA’s upcoming missions such as EarthCARE. Next to an impressive airborne fleet from AVATAR-T and CADDIWA components, situated on the island of Sal, intensive ground-based remote sensing and airborne in situ measurements performed on and above Mindelo in the framework of the ASKOS experiment. Specifically, a full ACTRIS remote sensing super site was deployed in Mindelo, Sao Vicente, including a multiwavelength-Raman-polarization lidar PollyXT, an AERONET sun photometer, a Scanning Doppler wind lidar, a microwave radiometer and a cloud radar. Additionally, ESA’s novel reference lidar system EVE, a combined linear/circular polarization lidar with Raman capabilities, was deployed, which can mimic the observations of the space-borne lidar onboard AEOLUS. Moreover, for 2 weeks in September, a light-weight airplane performed in-situ measurements in the aerosol layers around the island, in altitudes up to 3 km.

Here, will quickly introduce the measurements and present first results on the aerosols observed. Focus is given in the intensive September period, where very different aerosol conditions were observed above and around Mindelo. Usually, the marine boundary layer was up to 1 km and was topped by the Saharan Air Layer (SAL) reaching up to 6 km altitude. Three different dust events were observed. The first one had significant spatiotemporal homogeneity, which is ideal for Cal/Val objectives. The second one had strong horizontal and vertical gradients in composition and concentration and a significant anthropogenic component, making it ideal for an in-depth analysis with the synergistic dataset. After 22 of September, volcanic aerosols from the la Palma volcano were captured, mixed in the local boundary layer and partly above in the dust layer of the 3^rd dust event and relevant Aeolus overpass.

As a next step, science application studies are anticipated, using the wealth of information provided by ASKOS and JATAC campaigns, including already the following applications in the framework of ESA and EU projects:

• Long-range transport of the coarse and giant dust particles;
• Impact of non-sphericity on dust transport;
• Impact of electric charge on dust dynamics;
• Dust particle orientation;
• Impact of dust on radiation and dynamics;

Impact of dust deposition on ocean biogeochemistry;

How to cite: Amiridis, V. and the ASKOS team: The ASKOS experiment for desert dust science applications, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3633, https://doi.org/10.5194/egusphere-egu22-3633, 2022.

Global aerosol models and retrieval algorithms of remote sensing products generally approximate dust aerosols as spherical or spheroidal particles. However, measurements show that dust aerosols deviate substantially from spherical and spheroidal shapes, as ratios of dust length to width (the aspect ratio) and height to width (the height‐to‐width ratio) deviate substantially from unity. Here, we quantify dust asphericity by compiling dozens of measurements of aspect ratio and height‐to‐width ratio across the globe. We find that the dust length is on average 5 times larger than the height and that aerosol models and retrieval algorithms underestimate this asphericity by a factor of ~3 to 5. We find little difference in the average shape of North African dust and Asian dust, although North African dust becomes more aspherical during transport, whereas Asian dust might become less aspherical. We further find that both aspect ratio and height-to-width ratio show little dependence on dust particle size. These findings enable simple parameterizations of dust shape distributions that can be considered approximately representative of the global population of atmospheric dust.

We use these globally representative dust shape distributions to quantify the effects of dust asphericity on deposition and optics. We find that accounting for dust asphericity increases the gravitational settling lifetime by ~20%, which helps explain the underestimation of coarse dust transport by models. We further find that, relative to the ellipsoidal dust optics accounting for realistic dust asphericity, the spherical dust optics used in models  underestimate dust mass extinction efficiency, single-scattering albedo, and asymmetry factor for almost all dust sizes at both shortwave and longwave spectra. The ellipsoidal dust optics can reproduce the measured scattering matrix of feldspar and linear depolarization ratio substantially better than the spheroidal dust optics used in most retrieval algorithms. Thus, the globally representative dust shape distributions have a strong potential to improve global aerosol models and retrieval algorithms of remote sensing products.

How to cite: Huang, Y. and Kok, J. F.: The observationally constrained shape distributions of atmospheric dust, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13104, https://doi.org/10.5194/egusphere-egu22-13104, 2022.

We present preliminary results from the project OPTAIR, aimed to study the optical properties of airborne particles at Concordia Station, on the East Antarctic plateau, and to assess the relationship among the optical properties of particles suspended in air and deposited by the snow. Light scattering data from single particles are collected continuously by a permanent device installed in November 2018, operating the novel Single Particle Extinction and Scattering method and some traditional scattering measurements. Data are put in correlation with LIDAR measurements, with the aim to assess the impact on past and present climate. Results from the Antarctic season 2019 will be presented, showing clear evidence of remarkable changes in the amount of particles, size and optical properties across the year. In particular, about one third of the total cumulative dust particles accumulated in one year is advected during fast dust-rich air mass subsidence events lasting a few hours. This feature is of major importance to glaciological studies based on integrated, multi-annual snow and ice samples.

How to cite: Potenza, M., Delmonte, B., Del Guasta, M., and Cremonesi, L.: Year-round optical properties of atmospheric mineral dust particles at Dome C (East Antarctica): radiative and paleoclimatic implications, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11308, https://doi.org/10.5194/egusphere-egu22-11308, 2022.

There is much information to be derived from the airborne dust that can be found in ice cores, especially about the aerosol composition and sources, including the characteristics of the atmosphere of several thousands of years ago. There is, in fact, much still to learn about both the data that can be retrieved and how to interpret them with appropriate models. One of the most striking aspects of these tiny particles is the effect their shape alone has on their scattering and absorption properties, which translate into a contribution to the Earth radiative transfer, especially at the wavelength scale. We show that aggregates of several particles behave differently from compact particles, and non-isometric compact particles can be clearly distinguished from isometric particles as their non-sphericity increases. We report the advances in this direction based on light scattering measurements on the dust content of ice cores drilled from Dome C and Dome B in Antarctica as part of the EPICA project, and provide a physical interpretation in terms of the known models in the field of light scattering by small particles.

How to cite: Cremonesi, L., Delmonte, B., Ravasio, C., Artoni, C., and Potenza, M.: On the optical properties of mineral dust in ice-cores as revealed by light scattering techniques, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12517, https://doi.org/10.5194/egusphere-egu22-12517, 2022.

Mineral dust is an important type of ice nucleating particles in the troposphere; however, the effects of heterogeneous reactions on ice nucleation (IN) activities of mineral dust remain to be elucidated. A droplet-freezing apparatus (Guangzhou Institute of Geochemistry Ice Nucleation Apparatus, GIGINA) was developed in this work to measure IN activities of atmospheric particles in the immersion freezing mode, and its performance was validated by a series of experimental characterizations. This apparatus was then employed to measure IN activities of feldspar and Arizona Test Dust (ATD) particles before and after heterogeneous reaction with NO₂ (10±0.5 ppmv) at 40% relative humidity. The fractional surface coverage of nitrate, θ(NO₃^-), increased to 3.1±0.2 for feldspar after reaction with NO₂ for 6 h, and meanwhile the active site density per unit surface area (n_s) at -20 ^oC was reduced from 92±5 to <1.0cm^-2 by about two orders of magnitude; however, no changes in nitrate content or IN activities were observed for further increase in reaction time (up to 24 h). Both nitrate content and IN activities changed continuously with reaction time (up to 24 h) for ATD particles; after reaction with NO₂ for 24 h, θ(NO₃^-) increased to 1.4±0.1 and n_s at -20 ^oC was reduced from 20±4 to 9.7±1.9 cm^-2 by a factor of ~2. Our work suggests that heterogeneous reaction with NO₂ may significantly reduce IN activities of mineral dust in the immersion freezing mode.

How to cite: Chen, L., Peng, C., Chen, J., Chen, J., Wu, Z., and Tang, M.: Effects of heterogeneous reaction with NO2 on ice nucleation activities of feldspar and Arizona Test Dust, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-788, https://doi.org/10.5194/egusphere-egu22-788, 2022.

Dust storms are common meteorological disasters which occur frequently in the late spring and early summer in arid and semi-arid areas. Deserts in North Africa, Middle East Asia, Western Australia and Western North America are the most important dust-prone areas in the world. Along with the dust storm, salt components originated from inland saline lake and playas are often mixed with dust and transported to long distances. Dust/salt mixtures from the source of East Asian Dust Storm have great impacts on atmospheric chemistry processes and climate system due to their high hygroscopicity and efficient ice nucleation ability.

In this study, dust/salt mixture samples are collected from important sources of East Asian Dust Storm, i.e., Badain Jaran Desert, Tengger Desert and Ulan Buh Desert in northwestern China. Ion chromatography (IC) measurements were performed to determine the concentrations of cations (Na⁺, K⁺, Mg²⁺, Ca²⁺, and NH₄⁺) and anions (Cl⁻, SO₄²⁻, NO₃⁻, NO₂⁻, and F⁻). Synchrotron-based scanning transmission X-ray microscopy (STXM) was carried out to show the morphology and chemical mapping of typical dust/salt particles. Hygroscopic properties of the samples are measured by a vapor sorption analyzer, and a thermodynamic model is used to predict the deliquescence relative humidity (DRH) based on chemical composition of the samples. To further understand the linkages between the physiochemical properties and the origins/types of the samples, we performed positive matrix factorization (PMF) receptor model to analyze the results of the IC and the DRH results. In addition, the ice nucleation abilities were conducted with the portable ice nucleation chamber II (PINCii), where both homogeneous freezing and deposition nucleation were observed on the dust/particle aerosol particles/droplets.

How to cite: Li, J., Liu, W., Wenjun, W., Li, L., Tang, M., Hallquist, M., Wang, S., and Kong, X.: Hygroscopicity and Ice Nucleation Properties of Dust/Salt Mixture Originated from the Source of East Asian Dust Storm, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1278, https://doi.org/10.5194/egusphere-egu22-1278, 2022.

Chemical processing of reactive nitrogen species, especially NO_x(=NO+NO₂) and nitrous acid (HONO), determines/alters critically the photochemical ozone production in the troposphere, affecting the climate change, biological cycle and human healthy. However, the characteristics and sources of nitrous acid (HONO) and NO_x in the remote marine atmosphere are still poorly understood. Herein, based on the data sets of HONO-related species as well as other parameters measured during MarParCloud campaign at Cape Verde in October 2017, the multiphase chemistry model SPACCIM equipped with the state-of-the-art multiphase chemistry mechanism CAPRAM was adopted with input of current literature parametrizations for various HONO sources in the tropospheric boundary layer (gas reaction of NO and OH, ocean-surface-mediated conversion of NO₂ to HONO, NO₂ reacted with organics on mineral dust, NH₃ oxidation process, and dust-surface-photocatalytic conversions of reactive nitrogen species to HONO) to reveal the relative importance of each source for HONO in the remote boundary layer at Cape Verde. Each simulation was performed for 72 hours in different clusters obtained from the backward trajectories model analysis with HYSPLIT. The simulations well reproduced the observed HONO level and its diurnal pattern, and significantly improved the model performance for NO_x and O₃ in every cluster after 72 hours of operation, when considering the mechanisms of dust-surface-photocatalytic conversions of reactive nitrogen species. Furthermore, photolysis of the absorbed HNO₃ on the dust is modelled to be the prevailing contributor for the daytime HONO at Cape Verde, which accounted for about 56%, following by the photo-enhanced of NO₂ absorbed on the dust (41%). In contrast, the ocean-surface-mediated conversion of NO₂ to HONO and other pathways were found unimportant for HONO formation at Cape Verde. For OH sources, HONO photolysis only accounted for a small proportion source (~3%) of the ambient OH level in remote marine boundary layer due to the low HONO concentration at Cape Verde. In summary, this study highlights the key role of dust aerosols in the formation of HONO and NO_x at Cape Verde.

How to cite: Tilgner, A., Jiang, Y., Hoffmann, E. H., and Herrmann, H.: Insights into NOx and HONO in the subtropical marine boundary layer during MarParCloud campaign at Cape Verde, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4609, https://doi.org/10.5194/egusphere-egu22-4609, 2022.

Aerosol deposition is a major source of soluble Fe in open oceans, affecting marine biogeochemistry and primary production. However, Fe fractional solubility, a key parameter in estimating deposition fluxes of soluble aerosol Fe, is still highly uncertain. Abundance and fractional solubility of aerosol Fe in fine and coarse particles was measured at Qingdao (a coastal city in northern China) in November-December 2019. Average concentrations of total and soluble Fe were found to be 798±466 and 7.7±14.5 ng/m³ in coarse particles, and 801±534 and 7.3±7.6 ng/m³ in fine particles. Total Fe was well correlated with total Al for both fine and coarse particles, whereas soluble Fe was correlated with total Al for coarse particle but not for fine particles. Fe solubility was significantly lower in coarse particles (average: 0.80±1.03%) than fine particles (average 1.29±1.41%), and inverse relationship was observed between Fe solubility and total Fe concentration for fine particles but not for coarse particles. Compared to clean days, total Fe concentration was substantially increased during dust and haze days; however, Fe solubility was significantly reduced in dust days and elevated in haze days. Primary emission and secondary formation both contributed significantly to enhanced Fe solubility for both fine and coarse particles. Higher Fe solubility (>1%) in fine and coarse particles was usually observed at high aerosol acidity (pH<4) and high RH (>60%), suggesting critical roles of aerosol acidity and RH in regulating aerosol Fe solubility.

How to cite: Tang, M., Zhang, H., Li, R., and Dong, S.: Abundance and fractional solubility of aerosol iron during winter at a coastal city in northern China, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1, https://doi.org/10.5194/egusphere-egu22-1, 2022.

Volcanic eruptions release large amounts of ash in the atmosphere, accounting for 5 - 7.5% of the total primary aerosol emission. The accompanying outgassing emits mostly water, carbon dioxide and sulfur dioxide (SO₂). During the 2010 eruption of the Eyjafjallajokull volcano, an average SO₂ mixing ratio of 40 ppb was measured in the plume [1]. Volcanic areas such as Iceland are very active aeolian regions; as a consequence, 30 to 40 Tg of previously deposited Icelandic volcanic dust are re-suspended by winds annually [2]. In this environment, SO₂ can interact with volcanic dust (v-dust) in the presence of water vapour and UV light. Assessing the heterogeneous interaction of SO₂ with the surface of v-dust under UV-irradiation is therefore of crucial importance to understand its budget. Moreover, the quantification of SO₂ uptake by v-dust is necessary to understand the global SO₂ cycle, and to implement models with laboratory data characterizing heterogeneous processes [3].

To this aim, we have investigated the interaction of SO₂ with the surface of natural Icelandic v-dust samples with laboratory experiments [4,5]. A Coated-Wall Flow Tube reactor allowed determination of the steady-state uptake (γ_SS) and of the transient number of SO₂ molecules taken up by v-dust (N_S) in a broad range of relative humidity (0.1%<RH<72%) and irradiance (J_NO2 = 0-4.5×10^-3 s^-1) values. Interestingly, γ_SS values are the same in the dark and under UV-irradiation. N_S values however, largely increase under UV-irradiation, and with RH. Moreover, the amplification factor N_S,UV/N_S,dark increases linearly with: (i) the surface Ti concentration, (ii) the photon flux, and (iii) RH. These results reveal the importance of the heterogeneous photo-enhanced reactivity of SO₂ on natural v-dust samples, and advocate for a better inclusion of these processes in atmospheric models.

¹ Heue et al., Atmos. Chem. Phys. 11, 2973 (2011)

² Arnalds et al., Aeolian Res. 20, 176 (2016)

³ Maters et al., J. Geophys. Res. - Atmos. 122, 10077 (2017)

⁴ Urupina et al., Atmos. Environ. 217, 116942 (2019)

⁵ Lasne et al., Env. Sci. Atm., in revision

How to cite: Lasne, J., Urupina, D., Maters, E., Delmelle, P., Dagsson-Waldhauserova, P., Romanias, M., and Thevenet, F.: Daylight Promotes a Transient Uptake of SO2 by Icelandic Volcanic Dust, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9808, https://doi.org/10.5194/egusphere-egu22-9808, 2022.

Cryoconite is a dark-colored supraglacial dust which may be found in polar and mountain regions in the world. These sediments represent a combination of mineral particles, black carbon and organic matter. Cryoconite is considered as a microbial hotspot on an uninhabited surface of glaciers as well as material which influence the level of albedo. Due to relatively similar microbiological and physicochemical features of cryoconite it could take part in development of primary soils. This is important because of current rapid deglaciation in the Caucasus region which will intensify due to ongoing climate change.

The purpose of this research is to study physicochemical features of cryoconite, other types of sediments and cryoconite derived periglacial soils in Caucasus region, Kabardino-Balkarian republic as well as local Chernozems. Samples of cryoconite, moraines and mudflows were collected at Bezengi Glacier, the largest valley glacier at the Caucasus mountains. Cryoconite derived soils were collected in the adjacent Khulamo-Bezengi Gorge; Chernozems and fresh mudflow material were sampled at Baksan Gorge. Soil acidity (H₂O, CaCl₂), total organic carbon (TOC), basal respiration values and particle-size distribution were determined under laboratory conditions.

Almost all samples of materials from the Bezengi Glacier as well as Chernozems were characterized by a neutral reaction, while some samples of mountain soils of the Khulamo-Bezengi Gorge were characterized as slightly acidic and acidic, especially with regard to exchangeable acidity. Basal respiration values range from 2.20 mg of CO₂ per day in fresh mudflow to 35.09 mg of CO₂ per day in the upper horizon of mountain soils. In general, relatively high values of basal respiration were typical for mountain soils, which also has been observed in cryoconite from cracks and holes due to high amount of easily accessible organic matter. Most of cryoconite and moraines from the Bezengi Glacier were characterized by a low content of organic carbon (about 0.10%), while in the upper horizons of mountain soils these values were the highest (up to 7.54%) due to input of cryoconite material in soils through water streams in the warm period of the year.

Cryoconite and moraines were characterized by the predominance of coarse earth fraction while soils were characterized by the dominance of fine earth material. The study of particle-size of cryoconites and other materials from the Bezengi Glacier showed the dominance of the sand fraction (d=0.05-1mm). Fresh mudslides from the Baksan Gorge and mountain soils of the Khulamo-Bezengi Gorge were characterized in the same way. Chernozems of the Baksan Gorge were characterized by a high content of silt and clay fractions, which makes it possible to classify them as clay and clay loam.

This work was supported by Russian Foundation for Basic Research, project No 19-05-50107 “The role of microparticles of organic carbon in degradation of ice cover of polar regions of the Earth”.

How to cite: Kushnov, I., Abakumov, E., Lakhtionova, A., Tembotov, R., and Zubrzycki, S.: Key chemical characteristics of cryoconite sediments from Bezengi glacier and local mountain soils in the Caucasus mountains, Russia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5262, https://doi.org/10.5194/egusphere-egu22-5262, 2022.

Dust in the Earth´s atmosphere and deposition rates are both increasing in last decades. The south of Iberian Peninsula is deeply affected by air masses coming from Africa, one of the largest sources of atmospheric dust in the world (50%–70% of total emissions worldwide). Granada city (south of the Iberian Peninsula) has one of Spain’s highest atmospheric pollution levels (including particulate matter). African dust intrusion should be considered in the Iberian Peninsula because of the proximity of the Sahara Desert. Dust properties allows for a hypothesis on dust-provenance and dust-origin. Our study characterised atmospheric dust collected in Granada city during three monthly periods: 4PA (2012), 16PA (2013), and 28PA (2014). The main goal was to determine dust characteristics and genesis using a set of different techniques. The backward trajectories study separated the samples, according to their Saharan influence, into two groups: a) scarce influence (sample 16PA, 6% of days with Saharan influence); b) greater influence (samples 4PA and 28PA, ≈30% of days with Saharan influence). The two groups was confirmed by all the properties analysed, namely, PM10 concentration, deposition rates, grain size, mineralogy, and elemental composition (minor, including rare earth elements). Our samples showed similarities with soils from the Iberian Peninsula and other atmospheric dust collected in Granada. A remarkable discover was that particle morphology and surface microtextures on atmospheric quartz also verified the grouping. A principal component analysis of the quartz shape parameters insists on the differentiation of these groups, therefore we propose, as a fingerprint of provenance, the morphoscopy of atmospheric quartz grains (a main component of atmospheric dust).

How to cite: Molinero-García, A., Martín-García, J. M., Fernández-González, M. V., and Delgado, R.: Fingerprints of provenance in atmospheric dust collected at Granada city (Southern Iberian Peninsula)., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7117, https://doi.org/10.5194/egusphere-egu22-7117, 2022.

Phosphorus is a critical nutrient affecting primary productivity in large areas of oceanic oligotrophic and ultraoligotrophic ecosystems. The principal source of externally supplied inorganic-P in such ecosystems is the atmosphere with dust considered as an important source. However, recent work showed that organic-P originating from bioaerosols and dust can supply as much bioavailable P as inorganic P in dust, and is thus critical for primary productivity. The presence of organic-P in atmospheric samples is typically inferred by subtraction of the amount of inorganic phosphorus from the total amount of phosphorus. At present, there is no direct method for organic-P determination. Direct speciation methods point to important sources (e.g., phospholipids from bioaerosol), but cannot account for the total amount of P in organic from. There is a need therefore to develop a method to directly identify P that are associated with organic compounds. Nuclear magnetic resonance (³¹P-NMR) spectroscopy can provide such a capability, as it has proven to be a powerful analytical tool for the molecular characterization of organic-P in marine plankton, sinking particles, high molecular weight dissolved organic matter and sediment. The ³¹P-NMR technique, however, has never been applied to atmospheric samples and is the focus of this study.

Here we analyze Total Suspended atmospheric Particles (TSP) collected during dust events (n=5) in the eastern Mediterranean by using a high-volume air sampler. These particles were then analyzed using magic angle spinning solid-state ³¹P-NMR. The results showed the typical functional groups in P speciation which were: orthophosphate and monophosphate esters sharing the same chemical shift (H₃PO₄ and RH₂-PO₄), phosphate diesters (R₁R₂ HPO₄) and pyrophosphate (H₄P₂O₇). No phosphonates were detected (C-P bond) in TSP samples. Monophosphate esters and diesters are mainly found in nucleotides and their derivatives (e.g., DNA, RNA, AMP, ADP, and ATP), phospholipids and flame retardants (OPEs), and as such they constitute the majority of atmospheric organic-P. The above-mentioned P-organic compounds have C-O-P bonds therefore they are easily hydrolysable in the marine environment by the alkaline phosphatase enzyme providing an important source of P in aquatic ecosystems. Finally, the results showed that the amount of organic-P estimated colorimetrically is about equal to that estimated by ³¹P NMR indicating that the latter technique can be successfully employed in atmospheric studies for P speciation.

How to cite: Violaki, K., Panagiotopoulos, C., Avalos, C. E., Pivetau, L., and Nenes, A.: Atmospheric phosphorus characterization by 31P-NMR during dust events and bioavailability implications, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10122, https://doi.org/10.5194/egusphere-egu22-10122, 2022.

East Asian dust aerosols play a vital role in the local and regional climate through its direct, indirect, and semidirect effects, but the dominant factors affecting the interannual variation of dust aerosols over East Asia and their regional differences remain unclear. This study verified the accuracy of MEERA-2 dust data in East Asia, analyzed the interannual trends of dust in East Asia from 2000 to 2019 using the MERRA-2 dust column mass density (DCMD) and identified the dominant factors affecting the interannual variation during the dusty season (March–July) by developing the regional multiple linear regression models, combined with correlation and partial correlation analysis. The comparison with the dust index (DI) calculated from ground-based observations of dust events frequency indicated that MERRA-2 DCMD exhibited high spatial agreement (R > 0.8) with ground-based observations in most regions (especially in the dust source region of North China). The trend analysis revealed that DCMD in East Asia decreased significantly after 2000, particularly in the dusty season (March–July). These significant decreases were generally highly correlated with increases in normalized differential vegetation index (NDVI), volumetric soil moisture (VSM), and precipitation (PPT) and with decreases in wind speed (WS). Furthermore, WS dominated the interannual variation in the dust concentration over the East Asian dust source regions and their downstream. By contrast, PPT, through its wet deposition effect, dominated the variation in the rest of the regions away from the dust source regions. The study findings may help clarify the associations between local meteorological and surface factors and long-term variations in dust aerosols over East Asia.

How to cite: Che, H., Yao, W., Gui, K., Wang, Y., and Zhang, X.: Identifying the dominant local factors of 2000-2019 changes in dust loading over East Asia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3363, https://doi.org/10.5194/egusphere-egu22-3363, 2022.

The wide region of Asia is one of the most densely populated places of the Earth, hosting a large percentage of the Εarth's population. Thus, changes in climate and weather conditions affect the lives of many people. In Asia, there are many desert areas, from which large amounts of Dust Aerosols (DA) are emitted into the atmosphere, where they remain suspended from a few hours up to several days. DA are able to travel thousands of miles away from their source areas, among which the largest ones are the Taklamakan and Gobi Deserts in Central & East Asia and the Tar Desert in the Indian subcontinent. Apart from them, there are also other smaller deserts in Asia, i.e. Badain Jaran, Tengger, which also contribute significant amounts of DA. Furthermore, the Aralkum, Kyzylkum and Karakum areas East of the Caspian Sea contribute high dust loadings, too.

DA is a major contributor of aerosol burden in the Earth’s atmosphere, significantly affecting weather and climate conditions, through various interactions with radiation and clouds, while also deteriorating air quality and causing a series of health problems. DA alter the energy balance of the Earth-Atmosphere system, as they absorb and scatter primarily the solar, but also the thermal infrared radiation, thus influencing climate from the local to regional and global scales. Besides, DA act as effective Cloud Condensation Nuclei (CCN) or Ice Nuclei (IN), modifying cloud albedo and coverage, as well as the produced precipitation. All these dust effects are intensified under Dust Aerosol Episodes (DAEs), i.e. conditions of unusually high dust loadings, which occur every year with varying frequency and intensity, but with distinct seasonal and spatial characteristics. DAEs are originally determined on, and refer to, a pixel level, whilst days with an extended spatial coverage of DAEs are named Dust Aerosol Episode Days (DAEDs). Finally, series of consequent DAEDs constitute Dust Aerosol Episode Cases (DAECs), which are spatiotemporally extended and intense dust episodes that deserve to be identified and studied in areas like Asia.

In the present study, a satellite algorithm is used to identify DAEDs over Asia and the Caspian Sea, aiming to determine their spatial and temporal distribution emphasizing their frequency of occurrence and the associated dust loadings. The algorithm uses as input daily spectral Aerosol Optical Depth (AOD) and Aerosol Index (AI) data from MODIS C6.1 and OMI OMAERUV databases, respectively, spanning the 16-year period from 2005 to 2020. It operates on a daily basis and 1deg x 1deg pixel level and detects the presence of DA by applying appropriate thresholds on Ångström Exponent (AE) (calculated using spectral AOD from MODIS) and AI. Subsequently, the algorithm determines the occurrence of DAEDs and DAECs, yielding their frequency of occurrence, as well as the associated dust optical depth (DOD) on monthly and annual timescales. Thus, the algorithm outputs enable to build a climatology of spatiotemporally extended Asian dust episodes, as well as to derive their year to year variability and tendencies over the 16-year study period.

How to cite: Belimezis, P., Hatzianastassiou, N., Gavrouzou, M., and Korras-Carraca, M.-B.: Spatiotemporal characteristics of Dust Aerosol Episodes over Asia and Caspian Sea based on contemporary climatological satellite data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9188, https://doi.org/10.5194/egusphere-egu22-9188, 2022.

Mineral dust has radiative and biogeochemical impacts, affects human health and soil fertility. The mineral dust cycle, i.e., dust emission, transport and deposition depends on meteorological parameters, in particular surface wind speed and precipitation. Climate change has lead to measurable change in surface temperature and precipitation regimes in the Sahel (e.g., Panthou et al., 2018) and is also expected to modify the surface winds that controls dust emissions and transport. 

Since 2006, mineral dust is monitored in the Sahel by the stations of the INDAAF network (https://indaaf.obs-mip.fr/). We used the PM₁₀ surface concentrations and the Aerosol Optical Depth (AOD) from the AERONET network measured in Cinzana (Mali) and Banizoumbou (Niger) to detect possible changes in the Sahelian atmospheric dust content. The Angstrom exponent is used to select situations where mineral dust is the dominant contributor to the AOD. PM₁₀ concentrations and AOD are significantly correlated but have distinct seasonal cycles, with a ratio PM₁₀/AOD peaking in August.

No clear trend on the annual and seasonal mean concentrations or AODs has been identified. When subtracting the mean seasonal cycle to the monthly median PM₁₀ concentration we observe a slight decrease of the residuals  in Cinzana (Mali) but no trend in the AOD. No correlation was found between the AOD or the PM₁₀ concentrations and the North Atlantic Oscillation Index but the PM₁₀ concentration tends to increase with the Sahelian drought index.  For most of the years, the PM₁₀ concentrations and AODs are lower when the maximum of the vegetation cover of the previous year (represented by satellite Normalized Vegetation Index) is higher. This may reflect the protective effect of the dry vegetation residues on dust emission. These results suggest that, for the measurement period (2006-2019), the variability of the dust content is mainly due to the seasonal cycle and that the year to year variability is so large that no trends can be detected. Longer time series, with a better temporal sampling, seem to be necessary to have a chance to detect a significant change.

How to cite: Lhotte, A., Marticorena, B., Coman, A., Bergametti, G., Rajot, J. L., Féron, A., and Gaimoz, C.: Statistical analysis of multi-annual time series of atmospheric mineral dust content in the Sahel. , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4989, https://doi.org/10.5194/egusphere-egu22-4989, 2022.

The formation of the ‘Aralkum’ desert in Central Asia, as a consequence of the severe desiccation of the Aral Sea since the 1960s, has created a major new source of dust aerosol in the region. Recently dried lakebeds can be efficient dust sources, due to the availability of readily erodible sediments, and as a dry lakebed with an area of over 60,000 km² exposed to wind erosion the Aralkum has become a significant driver of dust storms in the region. However due to a paucity of ground-based remote sensing sites in Central Asia it is difficult to quantify the behaviour and consequences of dust activity in the region.

Using the dust transport model COSMO-MUSCAT we perform a one-year simulation of dust emission from the Aralkum and other desiccating lakes in Central Asia, exploring the resultant dust emission and transport patterns and assessing the viability of measuring such dust using remote sensing techniques. Making use of the Global Surface Water dataset (produced by the Copernicus Programme) in order to define the surface water coverage in various epochs, we make estimates of dust emissions for the Central Asian and Middle Eastern region under three scenarios: 1) the ‘Past’, representative of water coverage in the 1980s; 2) the ‘Present’, representative of water coverage in the 2010s; and 3) the ‘Aralkum’ scenario, representing only dust emissions from the present-era Aralkum.

In the Present scenario we estimate that the Aralkum area (here considered as 43-47°N, 58-62°E) emitted 27.1 Tg of dust over the course of a year from March 2015 to March 2016, while in the Past scenario it emitted 14.3 Tg. However ~68% of these Aralkum emissions occurred when the cloud cover was > 95%, raising questions as to the extent to which dust storm activity from the Aralkum is measurable by standard remote sensing techniques. Exploring the patterns of wind direction and dust emission, we find that of the 27.1 Tg of dust emitted by the Aralkum during the Present scenario, 14.5 Tg were driven by westerly winds, and as a result of this the longest transport pathways are simulated to be to the east. This is in contrast to several previous studies (during previous years) of Aralkum dust which have shown more typical easterly and north-easterly dust emission patterns. Analysis of ERA5 wind data over a 15-year period reveals that there is a high degree of interannual variability as to the direction of the strongest surface winds over the Aralkum, and hence the directions of emitted dust will also vary substantially from year to year.

How to cite: Banks, J., Heinold, B., and Schepanski, K.: Modelling of the spatial and temporal patterns of dust storms emitted from the Aralkum (the former Aral Sea) in Central Asia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8438, https://doi.org/10.5194/egusphere-egu22-8438, 2022.

High Latitude Dust (HLD) contributes 5% to the global dust budget and active HLD sources cover > 500,000 km². Potential areas with high HLD emission are calculated to cover >1 670 000 km² (Meinander et al., in review). In Iceland, desert areas cover about 44,000 km², but the hyperactive dust hot spots of area < 1,000 km² are the most dust productive sources. Recent studies have shown that Icelandic dust travelled about 2,000 km to Svalbard and about 3,500 km to Balkan Peninsula. It estimated that about 7% of Icelandic dust can reach the high Arctic (N>80°). HLD was recognized as an important climate driver in Polar Regions in the IPCC Special Report on the Ocean and Cryosphere in a Changing Climate in 2019.

Long-term dust in situ measurements conducted in Arctic deserts of Iceland and Antarctic deserts of Eastern Antarctic Peninsula in 2018-2021 revealed some of the most severe dust storms in terms of particulate matter (PM) concentrations. While one-minute PM₁₀ concentrations is Iceland exceeded 50,000 μgm^-3, ten-min PM₁₀ means in James Ross Island, Antarctica exceeded 120 μgm^-3. The largest HLD field campaign was organized in Iceland in 2021 where 11 international institutions with > 70 instruments and 12 m tower conducted dust measurements (Barcelona Supercomputing Centre, Darmstadt, Berlin and Karlsruhe Universities, NASA, Czech University of Life sciences, Agricultural University of Iceland etc.). Preliminary results will be shown.

Icelandic dust has impacts on atmosphere, cryosphere, marine and terrestrial environments. It decreases albedo of both glacial ice/snow as well as mixed phase clouds via reduction in supercooled water content. There is also an evidence that volcanic dust particles scavenge efficiently SO₂ and NO₂ to form sulphites/sulfates and nitrous acid. High concentrations of volcanic dust and Eyjafjallajokull ash were associated with up to 20% decline in ozone concentrations in 2010. In marine environment, Icelandic dust with high total Fe content (10-13 wt%) and the initial Fe solubility of 0.08-0.6%, can impact primary productivity and nitrogen fixation in the N Atlantic Ocean, leading to additional carbon uptake.

There is also first HLD operational dust forecast for Icelandic dust available at the World Meteorological Organization Sand/Dust Storm Warning Advisory and Assessment System (WMO SDS-WAS) at https://sds-was.aemet.es/forecast-products/dust-forecasts/icelandic-dust-forecast. In 2020-2021, a total of 71 long-range dust events was identified from Iceland reaching Faroe Islands, United Kingdom, Ireland, and Scandinavia. HLD research community is growing and Icelandic Aerosol and Dust Association (IceDust) has 100 members from 47 institutions in 18 countries (https://icedustblog.wordpress.com, including references to this abstract).

Reference

Meinander, O., Dagsson-Waldhauserova, P., et al.: Newly identified climatically and environmentally significant high latitude dust sources, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2021-963, in review, 2021.

How to cite: Dagsson Waldhauserova, P., Meinander, O., Nickovic, S., Cvetkovic, B., Vukovic, A., Moroni, B., Kavan, J., Laska, K., Renard, J.-B., Burdova, N., and Arnalds, O.: The role of High Latitude Dust in changing climate: Severe dust storm observations in Iceland and Antarctica in 2020-2021, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10655, https://doi.org/10.5194/egusphere-egu22-10655, 2022.

Perturbation of the Earth’s radiation budget is a key factor for climate change. Such perturbations are caused either from changes in the incoming solar radiation at the top of atmosphere (TOA), i.e. astronomical changes, or from modifications in the absorbed and scattered solar radiation within the Earth-atmosphere system. It is known that the current climate change is mainly attributed to greenhouse gases and aerosols. However, opposite to the achieved significant improvement of our knowledge of the role of greenhouse gases, there is still high uncertainty in the estimations of the aerosol radiative effect, due to their high spatial and temporal variability and complex and changing physical, chemical and optical properties.

Dust Aerosols (DA) is a major contributor of the global aerosol burden, while they modify the Earth’s radiation budget through the absorption and scattering of solar radiation and the absorption and re-emission of terrestrial radiation. Such dust-radiation interactions are known as Direct Radiation Effect (DRE) and generally result in a shortwave cooling effect and a smaller longwave heating effect both at the Top of Atmosphere (TOA) and the Earth’s surface. However, these radiative effects vary significantly in space and time, depending on the DA physical and optical properties, as well as on the underlying surface reflectivity or their vertical position relative to clouds, resulting in changes of the magnitude or even the sign of DREs. These dust-radiation interactions are expected to be maximized when the DA loads and the available solar radiation amounts are high. Therefore, the study of DREs under episodic dust conditions over areas such as the climatically sensitive and threatened Mediterranean Basin (MB), especially on a three-dimensional basis, is of primary importance. This becomes even more challenging when the study involves spectral detailed radiative transfer models (RTMs) and three-dimensionally resolved aerosol optical and atmospheric properties.

Here, all-sky DRE of DA is estimated during a spatially and temporally extended Dust Aerosol Episode Case (DAEC) took place from 16 to 18 June 2016 over the MB. The studied DAEC is identified using a satellite algorithm, which uses aerosol optical properties. The dust DREs are computed using 3-D dust optical properties, namely dust optical depth, single scattering albedo and asymmetry parameter from the MERRA-2 reanalysis, and cloud (i.e., cloud amount, optical depth and top pressure) and other atmospheric properties from the International Satellite Cloud Climatology Project (ISCCP) as input data to the FORTH (Foundation for Research and Technology-Hellas) spectral radiative transfer model. The model runs, with and without DA, on a 3-hourly temporal and 0.5˚×0.625˚ horizontal spatial resolution for the 4-day period from 15 to 18 June 2016. The RTM output includes upwelling and downwelling solar fluxes, as well as DREs, at TOA, at the surface, and at 50 levels in the atmosphere. The vertical and horizontal variation of DA DREs are computed by producing and examining the respective DRE cross-sections, and finally the heating rates caused by the evolving dust episode are estimated in order to yield the radiative effect of dust on the dynamics of the Mediterranean atmosphere.

How to cite: Gavrouzou, M., Hatzianastassiou, N., Korras-Carraca, M.-B., Lolis, C., Matsoukas, C., Mihalopoulos, N., and Vardavas, I.: Direct radiative effects of an intense dust episode over the Mediterranean Basin (16-18 June 2016), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7041, https://doi.org/10.5194/egusphere-egu22-7041, 2022.

Aeolian river dust has been one of the significant local air quality concerns in central and southern Taiwan for a long time. Aeolian river dust is not only affecting local visibility and air quality but also causing adverse health effects. It has been demonstrated that long-term exposure to PM10, even the low-level concentrations, may induce adverse health effects such as pulmonary, respiratory diseases and even death. Moreover, Taiwan Environmental Protection Administration (EPA) indicated nine river-dust events occurring in western Taiwan between 1994 and 2017. However, due to global climate change, the frequency and intensity of extreme events, such as droughts, are increasing significantly, which may contribute to the occurrence of river dust events. Furthermore, in Taiwan, most studies have only focused on the Asian dust storms transported from China, while the spatial-temporal characterization and health implication of river dust events is still not widely understood. Therefore, in this study, to explore the causes and effects of river dust in Taiwan, we mainly analyze the PM10 concentration, relevant hydro-meteorological factors (temperature, precipitation, relative humidity, wind speed, and river water level), drought events, and medical data of respiratory diseases by using time-frequency analysis. Time-frequency analysis is a tool that allows us to investigate the characteristic time scale and energy distribution of the signals since the signals are most likely to be both nonlinear and nonstationary, which cannot be adaptively analyzed by traditional data-analysis methods such as Fourier transform. Thus, the method of improved complete ensemble empirical mode decomposition with adaptive noise (ICEEMDAN) is introduced in this study to adaptively decompose hydro-meteorological time series and medical data into their intrinsic mode functions (IMFs) and a trend. Moreover, the time-dependent intrinsic correlation method (TDIC) is introduced to calculate the running correlation coefficient between two IMFs with the sliding window in different time scales. After the ICEEMDAN and TDIC work, the correlation between river dust and relevant hydro-meteorological factors can be identified. The impact of frequency and intensity of droughts on river dust events in Taiwan can be explored, and then the association between respiratory diseases and river dust can be determined. It is hoped that the results of this study can assist in promoting the related air pollution policies in protecting residents and reducing the risk of disaster to people, particularly during droughts when most of the river dust events prevail.

How to cite: Chen, C.-K. and Tsai, C. W.: Aeolian River Dust in Central and Southern Taiwan Rivers: Spatial-Temporal Characterization and Public Health Implication, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7031, https://doi.org/10.5194/egusphere-egu22-7031, 2022.

The dynamics of emissions of radioactive aerosols during powerful wildfires (3-23 April 2020) and dust storm (16-17 April 2020) in the Chernobyl Exclusion Zone (ChEZ) was estimated using an ensemble inverse method. The unique feature of this event is that the wildfires of unprecedented power in ChEZ were combined with the dust storm on 16-17 April 2020, which covered the Northern-West and Central Ukraine. Due to both events, the levels of Cs-137 concentrations in air were increased significantly above the background levels. In our study, the ensemble covariance matrices of model errors were calculated by a series of runs of the FLEXPART atmospheric transport model using different input meteorological data (22 meteorological datasets produced by Global Ensemble Forecasting System GEFS) and different sets of model parameters describing the size distribution of particles and height distribution of releases. Simulations covered the period from 3rd to 27th of April 2020. The prior estimates for the temporal dynamics of emissions were taken from [1]. Measurements of Cs-137 concentration in air collected by different countries and presented in [2] were used for source inversion. The vertical extensions of releases from different sources were estimated based on the data of the CAMS Global Fire Assimilation System. The fractions of emissions below plume bottom and between plume bottom and plume top heights were allowed to vary in different ensemble runs. It is shown that varying all the mentioned parameters (meteorological data, particle size distribution, and the parameters of emission distribution by height) significantly affected the results of the calculated temporal dynamics of emissions during the wildfires. However, the variability of meteorological data had the largest overall influence on the results. Confidence intervals for emissions from wildfires and dust storm (16-17 April) were obtained by processing the ensemble of estimates. The estimated total emissions of Cs-137 from the wildfires ranged from about 200 to about 1000 GBq. The total estimates of Cs-137 emissions due to the dust storm estimated by inverse modeling appeared to be considerably less than the emissions from the wildfires on the same days. At the same time, the levels of air pollution by common contaminants (PM2.5 and ash) observed in Kyiv were strongly dominated by the dust storm because the area covered by the dust storm was much greater than the area of ChEZ.

References

• Talerko, M., Kovalets, I., Lev, T., Igarashi,  Y., Romanenko, O.  (2021) Simulation study of the radionuclide atmospheric transport after wildland fires in the Chernobyl Exclusion Zone in April 2020. Atmospheric Pollution Research, 12(3) 193-204. DOI:1016/j.apr.2021.01.010
• Masson O., Romanenko O., Saunier O., Kirieiev S., Protsak V., Laptev G., Voitsekhovych O., Durand V., Coppin F. [et al.] (2021) Europe-Wide Atmospheric Radionuclide Dispersion by Unprecedented Wildfires in the Chernobyl Exclusion Zone, April 2020. Environmental Science & Technology, 55(20) 13834-13848. DOI: 10.1021/acs.est.1c03314

How to cite: Kovalets, I., Talerko, M., Synkevych, R., Koval, S., and Udovenko, O.: Emissions of radioactive aerosols during wildfires and dust storm in Chernobyl Exclusion Zone in April 2020 estimated by means of ensemble inverse modeling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-670, https://doi.org/10.5194/egusphere-egu22-670, 2022.

Mineral dust is the most abundant aerosol in the atmosphere and in particular regions exists in high concentrations. Ingestion of dust by aircraft engines can result in erosion, corrosion or a build-up of deposits damaging internal components. A move towards more efficient engines over recent years restricts capacity to tolerate detrimental impacts in engines. Air traffic in arid areas such as the Middle East has also increased dust exposure. However, it is not currently known how much dust is ingested by aircraft during take-off and landing. In order to quantify this, the vertical profile of dust is required. Here we present a climatology of vertical profiles of dust from the ECMWF Copernicus Atmospheric Monitoring System (CAMS) reanalysis at 10 major global airports, as well as their seasonal and diurnal variability, between 2003-2020. We evaluate the CAMS dust profiles against spaceborne lidar retrievals of dust from the Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument aboard the CALIPSO satellite using both the standard NASA Level 3 product and the LIdar climatology of Vertical Aerosol Structure (LIVAS) product. Finally, using expected aircraft ascent and descent rates and associated mass flow into an engine, dust dose is calculated for take-off, climb, descent, hold, approach, land and taxi phases, as well as for the entire ascent/descent at different airports, using both CAMS and CALIOP datasets.

We show that vertical distribution of dust varies significantly between airports and across seasons, which has a large impact on the total engine dust ingestion. Diurnal dust variations at some airports such as Dubai are extremely large, with night time surface concentrations reduced by over 20%.  Vertical profiles from CAMS show considerable differences to the standard CALIOP L3 retrievals, though agreement with LIVAS profiles is much better. Aircraft engine dose is found to be highest for Delhi (where does exceed 7g for a single descent in summer), Niamey and Dubai. During ascent, ingestion is largest during take-off, such that airports with large concentrations of lower altitude dust incur higher doses. During descent, dose is strongly dependent of the altitude of holding pattern relative to the altitude of maximum dust concentration, such that Delhi and Dubai incur the largest dust dose. Therefore, it is recommended that measures to reduce dust ingestion are airport-specific, and could include practices such as night time take-off and adjustment of holding pattern altitude.

How to cite: Ryder, C., Bezier, C., Dacre, H., Clarkson, R., Marinou, E., Proestakis, M., Alexiou, A., Amiridis, V., Kipling, Z., Benedetti, A., and Parrington, M.: Aircraft Engine Dust Ingestion at Major Global Airports, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2465, https://doi.org/10.5194/egusphere-egu22-2465, 2022.

Large-scale dust storms over North Africa transport mineral dust over thousands of kilometers equatorward and into the Mediterranean, thereby affecting human health and infrastructures. Dry Intrusions (DIs) are synoptic-scale descending airstreams from the midlatitude upper troposphere towards the surface. DIs occur behind midlatitude troughs and cyclones, and were shown to induce potential instability and enhance surface wind in the planetary boundary layer. Thus, DIs can potentially play a major role in the emission and transport of dust over North Africa.

Here, we aim to understand whether DIs are a common element that can link Rossby wave breaking, a known precursor of large emission events, to the high surface dust concentrations in Lagrangian sense, and to further understand the role of DIs in dust emission. By focusing on selected events and compiling a climatology for the years 2003-2018 we specifically aim to quantify the link between the co-occurrence of DIs and dust events, and identify common precursors. Using the Copernicus Atmosphere Monitoring Service (CAMS) reanalyzed dust optical depth (DOD), vertical dust mixing ratios, atmospheric fields from ERA-Interim reanalysis and a Lagrangian-based detection of DIs, we identify DI-dust events by applying a systematic matching algorithm.

We find that DI-dust events typically peak in winter to spring, and are associated with the maximal dust concentrations in the region. Multiple Rossby wave breakings in the eastern North Atlantic is a common precursor to DI-dust events. The DI airstream is found to connect the upper-tropospheric ridge/trough to the highest surface dust concentrations. Typically, a Mediterranean cyclone further steers the dust over North Africa and northward into the Mediterranean and Europe/Middle East. Vertical profiles of dust mixing ratios show that dust can reach the upper troposphere in the vicinity of the cyclone, attesting to long-range dust transport into the Mediterranean Sea and Europe.

Overall, our detailed case studies and climatological results emphasize the central role of DIs in producing large-scale dust storms. The distinct regional and seasonal frequency of DI-dust occurrence and their coherent precursor signals over the North Atlantic provide valuable information for understanding the predictability of such hazardous events.

How to cite: Fluck, E. and Raveh-Rubin, S.: Dry air intrusions link Rossby wave breaking to large-scale dust storms in North Africa, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-709, https://doi.org/10.5194/egusphere-egu22-709, 2022.

The long–range transport of larger than expected dust particles has been established in numerous observational studies. However, dust transport models struggle to simulate the observed particle size distributions. Studies utilizing a new version of WRF-chem code that contains the full size range of dust particles (0.2-100μm in diameter), estimated that approximately 80% reduction in the particles’ settling velocity is required for the particles to be transported from the desert towards the Cape Verde. Here, we examine the effect of the dust particles’ shape in the dynamics of coarse and giant long-range transport. We specifically apply a new drag coefficient for spheroids in idealized atmospheric WRF-chem simulations above the Atlantic Ocean. Additionally, since there is much confusion about the definition of the size of non-spherical dust particles, where some studies define size as the diameter of a sphere with the same volume, while others as the particles’ maximum, we perform simulations comparing the spherical and spheroid dust particles using both those two different approaches. The results are encouraging for the explanation of long –range dust transport, however more processes should be re-visited, including the dust radiation effects of non-spherical articles.

Acknowledgements

This research was supported by D-TECT (Grant Agreement 725698) funded by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme. Eleni Drakaki is funded by Stavros Niarchos Foundation (SNF) Fellowship.

How to cite: Drakaki, E., Amiridis, V., Tsekeri, A., Mallios, S., Papangelis, G., Spyrou, C., Ryder, C., and Katsafados, P.: Transport of non-spherical desert dust particles , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3703, https://doi.org/10.5194/egusphere-egu22-3703, 2022.

Desert dust is an important aerosol component that produces large uncertainties in assessments of Earth’s radiative budget and global climate change. However, current global climate model (GCM) simulations show that modeled dust poorly captures the observed dust in both spatial and temporal variability, which inhibits accurate assessments of aerosol radiative effects. Furthermore, dust emission is a local-scale process that varies on scales less than 1–10 km and thus current GCMs with typical grid-scale of > 100 km inherently have difficulties capturing dust spatial distribution and its sensitivity to local-scale meteorological variability. To tackle these problems, we develop a new dust emission scheme for GCMs that includes several more physical aeolian processes, and use the Community Earth System Model version 2.1 (CESM2.1) as a case study. First, we account for the dissipation of surface wind momentum by surface roughness elements included plants and rocks, which reduce the wind momentum exerted on the bare soil surface over deserts. The roughness of plants is a function of time-varying leaf area index (LAI), improving the sensitivity of the modeled emissions to climate and land use/land cover (LULC) changes. Second, we account for the effects of soil particle size distribution (PSD) on dust emission threshold by implementing a realistic soil median diameter inferred from a compilation of soil PSD observations. Third, we account for intermittent dust emissions induced by boundary-layer turbulence using a recently proposed saltation parameterization, which further couples dust with boundary-layer dynamics. With more aeolian processes, CESM2 dust emission matches better in spatial variability, seasonality, and dust activation frequency when compared against dust satellite retrievals. Modeled dust aerosol optical depth (DAOD) also shows better agreement in both spatial and temporal correlations with satellite-derived and ground-based AOD. Fourth, in addition to improving the description of aeolian processes, we conduct dust emission simulations across multiple grid resolutions and show that the high-resolution simulations generally produce a better dust spatial distribution. We then generate a map of correction factors to dust emissions for the coarse-gridded simulations to reduce the scale-dependency of dust emission parameterizations, and results indicate further improved agreement with dust observations for coarse-gridded CESM2. Our results suggest that including more physical processes into climate models can lessen bias, improve simulation results, and eliminate the use of empirical source functions. Therefore, our dust emission scheme could improve assessments of dust impacts on the Earth system and future climate changes.

How to cite: Leung, D., Kok, J., Li, L., Mahowald, N., Prigent, C., Okin, G., Klose, M., Pérez García-Pando, C., Menut, L., and Lawrence, D.: A new process-based and scale-respecting dust emission scheme for global climate models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13220, https://doi.org/10.5194/egusphere-egu22-13220, 2022.

The Integrated Forecasting System (IFS) of ECMWF is core of the Copernicus Atmosphere Monitoring Service (CAMS) to provide global analyses and forecasts of atmospheric composition, including reactive gases, as well as aerosol and greenhouse gases. Desert dust is simulated globally in three size bins. This system has been extended in an experimental version to prognostically simulate twelve mineralogical components of dust, each of them in three size bins. The chemical composition of dust can be derived from the mineralogical information, which allows for comparison against surface observations, notable of Iron. Each of the dust mineralogical component uses specific optical properties.

Four years of dust simulated global mineralogical and chemical composition have been produced. Iron from dust have been compared against observations of surface concentration worldwide and against simulations from the atmospheric iron model intercomparison organized by the Group of Experts on the Scientific Aspects of Marine Environmental Protection (GESAMP). Both evaluations gave satisfactory results. Surface concentration of other dust chemical components have been evaluated against surface observations other US and Europe.

Simulation of the dust mineralogy allows for a better representation of the geographical variation in dust absorption, especially depending on the simulated burden of the most absorbing species, hematite and goethite. While this variability cannot yet be represented in the optical properties of the dust species used operationally within CAMS, the climatology of dust mineralogy helped to derive new dust optical properties in the visible part of the spectrum. It also provided a degree of regional information about dust size distribution at emission, which has been implemented in the IFS. These two developments, together with an update of the dust source function, led to a significant improvement in the skill of the IFS system for dust related parameters. They have been included in the next operational upgrade of the operational global CAMS system, cycle 48R1, which is planned in late 2022.

How to cite: Remy, S., Kipling, Z., and Flemming, J.: Recent dust modeling developments in the ECMWF IFS in support to CAMS, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7852, https://doi.org/10.5194/egusphere-egu22-7852, 2022.

Dust emissions are linked with wind forces through a non-linear relationship. As a result, small errors in modelled wind speed lead to large errors in modelled dust emission. Dust models usually show satisfactory behaviour when dust outbreaks are caused by synoptic-scale weather systems. In contrast, smaller-scale dust events, e.g. haboobs or dust devils, are often unresolved at typical model resolutions and are hence unrepresented, in particular in coarse-grid global models. Haboobs are among the most important meteorological dust injection processes in the Sahara and Sahel in summer, both in terms of cumulative duration and intensity. The lack of haboobs or other unrepresented dust events likely leads to biases in the amount, spatial distribution, and seasonal variability of global dust emission and loading.

Here we present results of a high-resolution (~ 3 km), convection-permitting simulation for the year 2012 over northern Africa and the Middle East with the Multiscale Online Nonhydrostatic AtmospheRe CHemistry model (MONARCH). In contrast to previous studies, our simulations do not only contain meteorological variables at high resolution, but also include a full representation of the dust cycle. We assess the impact of resolution on the spatiotemporal dust patterns compared to observations and model simulations at coarser resolution. We also identify haboobs in the high-resolution simulation and assess their properties, such as occurrence frequency, duration, size/intensity, to investigate how realistically they are represented. 

How to cite: Klose, M., Unser, T., Basart, S., Jorba, O., Benincasa, F., Pantillon, F., Knippertz, P., and Pérez García-Pando, C.: High-resolution mineral dust modeling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9121, https://doi.org/10.5194/egusphere-egu22-9121, 2022.

Throughout the year, the Tropical Atlantic Ocean receives constantly enormous amounts of mineral particles emitted over the western Sahara. Despite the numerous efforts, the current state-of-the-art atmospheric-dust models are not yet able to represent adequately the Saharan dust outflows towards the Atlantic Ocean. Several drawbacks in the relevant parameterization schemes can explain this deficiency, which subsequently hampers an optimal assessment of the dust-induced impacts. One of these aspects is the wind acting as the driving force of dust emission and transport. Thanks to the deployment of the ALADIN (Atmospheric Laser Doppler Lidar) lidar, onboard the European Space Agency (ESA) Aeolus satellite, profiles of HLOS (Horizontal Line-Of-Sight) winds are acquired globally up to a maximum of 30 km altitude. This unique global dataset is filling an existing observational gap in the Tropics, among other regions of the planet. In addition, the assimilation of Aeolus HLOS winds has revealed an improvement in numerical weather predictions (NWP), particularly in the Tropics where the major portion of the global dust budget resides.

The improvements of NWP are expected to also advance dust numerical simulations. Such hypothesis is under investigation in the NEWTON (ImproviNg dust monitoring and forEcasting through Aeolus Wind daTa assimilatiON) project funded by ESA under the Aeolus+Innovation framework. To address the NEWTON scientific objective, short-term regional dust forecasts, relying on the WRF model operating at the National Observatory of Athens (NOA), are conducted. More specifically, two WRF runs are performed using boundary and initial conditions from the ECMWF IFS (Integrated Forecasting System) outputs, produced with (hel4) and without (hel1) the assimilation of Aeolus quality screened Rayleigh-clear and Mie-cloudy wind profiles. Our simulation domain encompasses most part of the Sahara Desert and the Atlantic Ocean, bounded between the Equator and mid-latitudes. Focus is given on September 2021, when the JATAC (Joint Aeolus Tropical Atlantic Campaign) campaign took place in Cape Verde providing reference observations (ground-based, airborne) valuable for a comprehensive evaluation of WRF dust-related outputs. The assessment analysis is further extended by utilizing the satellite dust datasets MIDAS (ModIs Dust AeroSol) and LIVAS (LIdar climatology of Vertical Aerosol Structure for space-based lidar simulation studies), both developed at NOA, providing columnar dust optical depth and vertical profiles of dust extinction, respectively. Finally, all the NEWTON related activities are disseminated via the official website (https://newton.space.noa.gr) and the EO4Society portal (https://eo4society.esa.int/).

How to cite: Gkikas, A. and the NEWTON team: Assessing the impact of Aeolus wind data assimilation on the Saharan dust simulations in the framework of the JATAC campaign, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3586, https://doi.org/10.5194/egusphere-egu22-3586, 2022.

How to cite: Kiriakidis, P., Gkikas, A., Papangelis, G., Kushta, J., Christoudias, T., Drakaki, E., Proestakis, E., Marinou, E., Gialitaki, A., Kampouri, A., Spyrou, C., Benedetti, A., Rennie, M., Straume, A. G., Retscher, C., Dandocsi, A., Sciare, J., and Amiridis, V.: The impact of assimilating AEOLUS wind data on regional Aeolian dust model simulations using WRF-Chem. , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-980, https://doi.org/10.5194/egusphere-egu22-980, 2022.

Unmanned Aerial Vehicle (UAV)-sensor systems allow for cost-effective vertically-resolved in-situ atmospheric observations within the lower troposphere. Taking advantage of the private runway and dedicated airspace of the Unmanned Systems Research Laboratory (USRL; https://usrl.cyi.ac.cy/) of the Cyprus Institute in Orounda (Nicosia, Cyprus), an intensive campaign focusing on mineral dust observations was conducted between 18 October and 18 November 2021. This, involved UAV flights (36 in total) and ground-based active and passive remote-sensing observations during two distinct dust outbreaks over Cyprus.

The first dust event occurred between 25 October and 1 November 2021, and HYSPLIT back-trajectories revealed that the observed air masses were mainly originated from NE Sahara (Libya, Egypt). The second dust event was observed from 13 to 18 November 2021. HYSPLIT back-trajectories revealed that the observed air masses at the beginning of the second event were originated from the Middle East (Saudi Arabia, Syria), but the air mass origin switched to NW Saharan dust midways through the event. The Aerosol Optical Depth at 500-nm as measured by our sun-photometers was found to be above 0.2 all the time, and in some days reached up to 0.5. The observed aerosol layers were found to be extending from ground up to 5 km Above Sea Level (ASL).

This study presents results of the vertical aerosol structure/height-resolved information of each dust event from its arrival to its departure as observed by instruments on-board the UAVs including: a pair of Universal Cloud and Aerosol Sounding System (UCASS) Optical Particle Counters (OPCs), Printed Optical Particle Spectrometer (POPS) OPC, Compact Optical Backscatter AerosoL Detector (COBALD) and filter samplers.

How to cite: Kezoudi, M., Papetta, A., Marenco, F., Keleshis, C., Kandler, K., Girdwood, J., Stopford, C., Wienhold, F., Ru-Shan, G., and Sciare, J.: Profiling mineral dust with UAV-based in-situ instrumentation (Cyprus Fall campaign 2021), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11209, https://doi.org/10.5194/egusphere-egu22-11209, 2022.

Atmospheric mineral dust constitutes one of the most important aerosols in terms of mass in the global atmosphere. Dust impacts on the Earth’s climate are closely related to its physical and chemical properties, i.e. its particle size distribution (PSD), mineralogical composition, particle shape, and mixing state. Despite the knowledge acquired on dust properties over the last decades, understanding of dust particle size and composition at emission is still incomplete, partly due to the scarcity of coincident PSD measurements for emitted dust and the parent soil. In this context, the ERC project FRAGMENT (FRontiers in dust minerAloGical coMposition and its Effects upoN climaTe) conducts dust field campaigns in different regions of the world, obtaining a detailed characterization of the soil, airborne particles and meteorology. The first measurement campaign took place in September 2019 at “El Bour”, a dry lake located in the Draa River Basin at the edge of the Sahara desert in Morocco.

Here, we provide an overview of the atmospheric conditions, the dynamical parameters characterizing the structure of the near-surface boundary layer and the wind erosion events of varying intensity that occurred during the measurement period. We explore the temporal variability of: (1) the size-resolved dust concentrations measured by two optical particle counters placed at 1.8 and 3.5 m height, (2) the associated diffusive dust flux calculated through the gradient method, (3) the measured saltation flux and (4) the sandblasting efficiency. We also evaluate the relationships of these variables with friction velocity and atmospheric stability. Finally, we analyse the PSDs of emitted dust concentrations and diffusive flux, and investigate their variability under different meteorological conditions.

How to cite: González-Flórez, C., Klose, M., Alastuey, A., Dupont, S., Etyemezian, V., González-Romero, A., Kandler, K., Nikolich, G., Pandolfi, M., Panta, A., Querol, X., Reche, C., Yus-Díez, J., and Pérez García-Pando, C.: Size distribution of emitted dust in Morocco, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11247, https://doi.org/10.5194/egusphere-egu22-11247, 2022.

The study was carried out using observations in a 5 km long and 200-300 m wide patch of loose sands, located west of the Naryn Khuduk settlement (Russia, 2013-2021). The uniqueness of this area is determined, in particular, by the structure of the Seif dune ridges extending approximately in the latitudinal direction. We used data on concentrations of microparticles (sizes from 0.2 to 5 μm) at two levels (0.5 and 2.0 m) with multichannel registration, on concentrations of microparticles with sizes from 0.4 to 30 μm at 0.2, 0.4, 0.8, 1.6 and 3.2 m, on electric field strength.

The size distribution of microparticles, the concentrations of coarse aerosol fraction [1] are higher when the wind is tangential to the extending of dune than when it is frontal. Concentration values at heights of 20 and 40 cm exceed by several times in profiles built up to a height of 3.2 m for angles of about 10-30º with respect to dune crest compared to other wind directions.

This related to the processes of abrasion of the coarse fraction of microparticles from the newly involved large particles from the zone of the leeward slope. The presence of heavy rolling or stationary particles is confirmed by the occurrence of ripples on the surface.

The connection with the change of wind direction suggests the importance of splashing and abrasion processes when particles fall behind the leeward slope. In this context the influence of an obstacle on air flow with particles suspended in it has been studied for the Lagrangian-Eulerian model by means of the open package OpenFOAM. The particles falling on the surface in the recirculation zone behind the leeward slope created a disturbance of turbulent energy, which contributes to the intensification of the dust aerosol carry out beyond the salting layer.

Microparticles up to 0.5 μm in size, adhere to the surface of saltation. For them, the action of forces of electric nature turns out to be essential [2]. They appear in a free state at the moment of critical charge accumulation on a saltation particle under the influence of electric field created by the flux of large particles moving near the surface. Analytical estimation of the relative change in electric field strength shows a quadratic dependence on the number of generated microparticles.

At wind speeds close to the threshold value and with the wind direction close to tangential with respect to the dune crest line  the electric field strength increases. Concentrations of arid aerosol with sizes 0.2-0.4 μm increase, which is associated with faster charging of saltation particles. This is explained by participation of larger particles in the process with strengthening of tunnel effect of electric charge transfer from larger particles to smaller ones.

The study was supported by the Russian Science Foundation project 20-17-00214.

• Malinovskaya E.A.et.al. Izvestiya, Atmospheric and Oceanic Physics 57(5) 2021
• Malinovskaya E.A.et.al. Doklady Earth Sciences, 502(2) 2022.

How to cite: Malinovskaya, E., Chkhetiani, O., and Maksimenkov, L.: On the effect of changes in wind direction on dust aerosol concentrations in the near-surface layer, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12723, https://doi.org/10.5194/egusphere-egu22-12723, 2022.

In the beginning of February 2021, a large dust plume travelled from the Sahara across the Mediterranean Sea and deposited a colorful layer of particles on the snow-covered slopes of the Pyrenees and the Alps. The event was widely reported in the media due to the surprising color of the sky and of the snow cover. 

To characterize the amount of dust deposited on the ground during this remarkable event, we organized a citizen science campaign. We collected 150 snow samples from which the deposited dust mass was measured over the Pyrenees, the French and the Swiss Alps. The analysis of all samples shows a robust deposition gradient from the Pyrenees to the Alps and enhanced deposition rates on south facing slopes in agreement with satellite data. The samples were used in combination with detailed snow modeling to evaluate the dramatic impact of the dust deposition on the melt and duration of the snow cover. 

How to cite: Dumont, M., Gascoin, S., Reveillet, M., and Voisin, D. and the Collectif neige orange: Orange snow and citizen science, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3132, https://doi.org/10.5194/egusphere-egu22-3132, 2022.

The Sahara Desert is the largest source of dust worldwide. Finland, north of 60 ^oN, is annually affected by long-range transported Saharan dust, which is most often observed as red sunrises and sunsets. Observations on dust deposition on ground are rare. On 23 February 2021, Saharan dust was transported and deposited in the southern part of Finland, reaching up a long way inland. At the time, the ground was covered with snow, and therefore the dust deposition was more easily detectable. The deposition was accompanied by freezing rain in the most southern part of the country, and snowfall further north.

Samples of dust in snow were collected by citizens and forwarded to the Finnish Meteorological Institute (FMI) following our researchers’ guidelines advertised in social media. Most samples were a solid residue from 2 dl of superficial snow, that had been either melted and filtered using coffee filters, evaporated on an aluminum foil, or decanted with the help of containers. In addition, fresh samples were collected for reference and were stored in a freezer for further analysis. Samples were received from over 500 locations and each of these contained one or more filtered, evaporated, or decanted dust samples. Dust was observed as far north as Vaasa and Kuopio (~63 ^oN).

The event was forecasted by the operational SILAM global atmospheric-composition suite of FMI (http://silam.fmi.fi) five days in advance. The suite is driven by the meteorology from the Integrated Forecasting System (IFS) model of the European Centre for Medium-Range Weather Forecast (ECMWF). According to the model results, the near-surface concentrations of desert dust in Finland on 23.02.2021 were negligible, while the total column reached 100-200 µg/m², and optical column thickness in some places was up to 0.2, which is enough to be visible. The scavenging of dust from aloft layers resulted in substantial contamination of snow. Light microscopy results indicate the presence of quartz particles in the range 5-15 µm compatible with desert dust. Processed samples from the Askola region (~60 °N), about 20 km north from the southern coastline, show depositions of ~1100 mg/m². Dust deposition amounts may vary greatly depending on the location and precipitation amounts. Our work also includes ice nucleation experiments, determination of particle size distributions, investigations on organic compounds, microplastics and microorganisms. The citizen science nature of the project will be used to promote and disseminate FMI’s research on aerosols through a specific outreach programme. Our study aims at producing information on latitudinal Saharan dust transport, as well as on deposition particle shapes, size distributions and ice nucleation ability of the particles detected in Finland, through the analysis of the collected samples.

How to cite: Meinander, O., Alvarez Piedehierro, A., Kouznetsov, R., Rontu, L., Welti, A., Kaakinen, A., Heikkinen, E., and Laaksonen, A.: Saharan dust transported and deposited in Finland on 23 February 2021, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4818, https://doi.org/10.5194/egusphere-egu22-4818, 2022.

Mineral dust plays an important role in the ocean’s carbon cycle through the input of nutrients and metals which potentially fertilise phytoplankton, and by ballasting organic matter from the surface ocean to the sea floor. However, time series and records of open-ocean dust deposition fluxes are sparse. Here, we present a series of Saharan dust collected  between 2015 and 2020 by dust-collecting buoys that are monitoring dust in the equatorial North Atlantic Ocean as well as by moored sediment traps at the buoys' positions at ~21°N/21°W and ~11°N/23°W. We present dust-flux data as well as particle-size distribution data, and make a comparison of the dust collected from the atmosphere at the ocean surface with the dust settling through the ocean and intercepted by the submarine sediment traps. See: www.nioz.nl/dust

How to cite: Stuut, J.-B., Guerreiro, C., Brummer, G.-J., and van der Does, M.: Monitoring present-day Saharan dust at sea, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5364, https://doi.org/10.5194/egusphere-egu22-5364, 2022.

Dust emission affects soil fertility through nutrient loss in source regions while dust deposition can represent a significant nutrient input for remote ecosystems. If the Sahel is a well-known dust source region, it is also a region where large amounts of dust from the Sahara desert are deposited.                                                         

To quantify the input of nutrients that mineral dust deposition represents for Sahelian soils and to identify the sources responsible for these deposits, a dedicated instrumental setup was deployed during two years in two Sahelian sites of the INDAAF Network : Bambey (Senegal) and Banizoumbou (Niger). The insoluble and the soluble fraction of the atmospheric deposits have been collected separately and analysed. In parallel,  the elemental composition and carbon content of PM₁₀ were determined. A special attention was given to the most important nutrients for the soil fertility in this region (P and N) and on the organic C. Other elements (Fe, Al, K, Ca, ...) were also analysed in order to identify the sources of the deposited particles.                                                

For most of the analysed elements, the elemental compositions of PM₁₀ and dust deposit are consistent and the dust samples composition reveals a seasonal change. During the dry season, the dust composition is similar in Niger and Senegal. During the wet season, mineral dust in Niger exhibits a typical signature of sahelian soils (i.e., enriched in Fe and depleted in Ca) while in Senegal dust composition suggests a regional source enriched in Ca. The analysis of the soluble and insoluble fraction of dust deposition allows to estimate the total annual amount of P, N and C deposited on Sahelian soil.

How to cite: Marecar, R., Marticorena, B., Bergametti, G., Galy-Lacaux, C., Losno, R., Rajot, J. L., Chevaillier, S., Feron, A., Triquet, S., and Dias-Alves, M.: Nutrient inputs to sahelian soil by atmospheric dust deposition , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4891, https://doi.org/10.5194/egusphere-egu22-4891, 2022.

Dust is a major aerosol in the atmosphere. Atmospheric dust originates from human activities or natural processes and the deposition of dust affects several ecological and biogeochemical processes. Lù’àn Mân (61°13’03’’ N, 138°37’34’’ W) is located between the Ruby Ranges on the east and the Kluane Ranges in the St. Elias mountains on the west, and on the traditional lands of Kluane, Champagne-Ashihik, and White River First Nations. Kaskawulsh Glacier, located 25 km from the A’ą̈y Chù (formerly the Slims River) delta, began to retreat in the nineteenth century and this retreat accelerated in the late twentieth and early twenty-first centuries. In 2016, Slims Lake had partially drained, leading the water to be re-routed from A’ ą̈y Chù into Kaskawulsh River. Therefore, the level of Lù’àn Mân fell, and the drying of the riverbed became an important source of aeolian sediments and important dust storms were observed. We studied dust and trace elements deposition in the area in lichens and soils. The objective of this study was to determine the impacts of dust deposition on trace elements concentrations in vegetation and soils along a deposition gradient. To do this, we sampled lichens (Peltigera canina) and soils at sixty sites in the zone affected by the dust storms. We analyzed six trace elements (Ni, Cu, Zn, As, Cd, Pb) by ICP-MS. The results showed that the sites close to the delta had higher trace element concentrations than the sites 10 and 20 km away.

How to cite: Pouillé, S., Talbot, J., and King, J.: Impacts of mineral dust on soils and vegetation at Lù’àn Mân (Kluane Lake), Yukon Territory)., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5258, https://doi.org/10.5194/egusphere-egu22-5258, 2022.

The loesses of central Ukraine, occurring on both sides of the submeridional-oriented Dnieper River valley, have the character of continuous patches up to 30 or even 50 meters thick. In geological exposures (mainly cliffs) they have the character of loess-palaeosol sequences, additionally separated by glacial till (Saalian), which plays an important role as a stratigraphic marker. The loess cover underlies the river sediments of the Pleistocene Dnieper terraces. A characteristic feature of the documented sequences is a clear difference in their thickness, as well as litho- and pedological formation on opposite banks of the Dnieper River.

Grain size analyses (laser and sieve) of a number of sequences on both sides of the river were conducted. The assumed constant interval was 5 cm. Based on the measurements, accurate statistical characterization of the individual fractions and subfractions was developed and a number of indices were calculated that may be of great value in environmental interpretations.

Paleogeographic conclusions from sedimentological studies were focused on the characterization of depositional environments. The basic conclusion is the documented great dissimilarity of grain size characteristics of lithological units of the same age on both sides of the Dnieper valley. This reflects the different nature and high variability of environmental conditions during accumulation period. The study clearly shows that the valley was an important source of windblown silty material, but also its morphologically diverse banks were important orographic barriers for aeolian transported material. Moreover, a strong connection between the investigated aeolian sediments and the older, underlying layers of different origin – glacial and fluvial – was demonstrated.

Research carried out as part of the grant of National Science Centre, Poland as the project no. 2018/31/B/ST10/01507 entitled “Global, regional and local factors determining the palaeoclimatic and palaeoenvironmental record in the Ukrainian loess-soil sequences along the Dnieper River Valley – from the proximal areas to the distal periglacial zone”.

How to cite: Mroczek, P., Łanczont, M., Komar, M., Nawrocki, J., Standzikowski, K., Hołub, B., Krokhmal, O., and Derevska, K.: Paleoenvironmental implications of grain size characteristics of loess key-sites from opposite banks of the Middle Dnieper River valley (Ukraine), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13524, https://doi.org/10.5194/egusphere-egu22-13524, 2022.

Loess deposits are well known as repositories of information about climatic and environmental variations occurring over the Quaternary. Over the years, numerous weathering indices relating to the geochemical characteristics of loess sediments have been developed to provide insights into environmental changes through time. In this study, we characterize the major element chemistry of the uppermost 20 m of the Karamaidan loess deposit in Tajikistan, which spans the last full glacial cycle. We compare major element ratios (Al/Ti, Fe/Ti, and Al/Fe), together with ternary A-CN-K diagram and enrichment/depletion of the elements relative to the upper continental crust, down the Karamaidan sequence, and compare our results to other regional and supraregional loess deposits and their change through time. We investigate different weathering indices (A and B indices, PWI, bases vs. Al ratio, CIW, PIA, and YANG indices, WI-1, WI-2, and CPA and FENG) in order to identify those most applicable to our study. We compare our results magnetic susceptibility down the stratigraphic profile to derive a direct index for alteration of the deposit.

How to cite: Aquino, A., Lezzerini, M., Scardia, G., Prud'Homme, C., Dave, A. K., Engström Johansson, A., Marquer, L., Safaraliev, N., and Fitzsimmons, K.: Application Of Geochemical Weathering Indices To Loess -Paleosol Sequences From Central Asia (Tajikistan), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12871, https://doi.org/10.5194/egusphere-egu22-12871, 2022.