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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.