In the ambient environment where gases and various particles coexist, pollen is a chief biological airborne particle among atmospheric bioaerosols. Despite its significance, pollen surveillance in many countries including India is overlooked as most of the air quality monitoring, predominantly targets PM_2.5, PM₁₀, or other gaseous pollutants. Pollens are not only vital for plant reproduction but they interact with various atmospheric elements, trigger allergies, influence genetic exchange and cause environmental shifts by fostering microorganism transmission. Despite their profound impacts, the epidemiological effects of pollens remain underexplored. Majority of the pollens aggravate diseases like asthma or COPD in human beings and, therefore the investigative studies on pollens become crucial for disease management. The sampling of pollens involves multiple parameters e.g., wind speed, turbulence, and orientation of sampler, affecting their concentrations. Suction-based impaction pollen samplers offer promising pollen sampling due to their adaptable cut points and high throughput. However, if such suction-based samplers are designed to match human breathing rates of 12-16 LPM and a D₅₀ of 2 µm, the retrieval of pollens is efficiently optimized. In this work, a rectangular slit-based pollen sampler was designed after carrying out extensive numerical modelling for creating a 3D design of the sampler. Further, the Computational Fluid Dynamic (CFD) employing Poly-Hexcore volume meshing, and a k-w turbulence model combined with the Discrete Phase Model (DPM). was used to validate the design of the sampler., The DPM includes particle sizes ranging from 2 – 100 µm with simulations carried out in two regions i.e., solid (slide) and fluid (air). The slide's boundary condition was set as ‘trap’ since it was coated with a sampling medium to capture pollens. Further, inlet and outlet boundary conditions were set as ‘escape’. The efficiency of pollen collection as observed from the simulations, ranged between 60% - 100%, gauged through particle trajectory and streamlines. Pollen collection efficiency was found to increase when staggered inlet and outlet mass flow geometry were used. Moreover, the use of a trapping sampling medium restricted particle jump-off, altering the particle cut-off point towards smaller sizes. This shift, while enhancing capture efficiency, also influenced the particle size range the sampler can effectively trap. In summary, the pollen sampler designed in this work exhibited a better collection efficiency compared to traditional samplers and was also representative of the pollen inhalation rate of human beings. Further, field testing was also done for the sampler to see the presence of pollen in ambient air.

How to cite: Dhawan, S., Kumar, A., Khare, M., and Mehta, D. S.: Design and Validation of a portable sampler to monitor pollens at street level in the ambient environment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-198, https://doi.org/10.5194/egusphere-egu24-198, 2024.

Estimating pollen profiles and assessing relationships with meteorology, air pollutants and vegetation in three cities of India

Arzoo Dhankhar¹, Sagnik Dey², Darsy Darssan³, Nicholas J Osborne³

¹UQIDAR (University of Queensland, Australia- Indian Institute of Technology, Delhi, India)

²Indian Institute of Technology, Delhi

³School of Public Health, University of Queensland, Australia

Allergy, is, showing an increasing incidence over recent decades across the globe. Less emphasised is the impact of bioaerosols particularly ‘pollen’ on adverse respiratory health effects. India has some of the poorest air quality globally making it an important study area. Regular monitoring of airborne pollen is crucial to know the current prevalence and diversity of potential pollen allergens present in the air column. But most of the LIC and LMICs lack regular pollen monitoring both spatially and temporally.

In this study, we collected daily bi-hourly airborne pollen samples from three cities in India (Delhi, Rishikesh and Kolkata) for 5 weeks. These samples were collected using small portable pollen samplers (pollen sniffers). The pollen were counted using microscopy and the results were analysed. The study focused on assessing the relationships between daily pollen counts (total and grass), meteorological parameters (wind speed, relative humidity, temperature, rainfall), vegetation and air pollutants (PM_2.5, PM₁₀, NOx, SOx, O₃).

Poaceae and Chenopodiaceae-Amaranthaceae families were found to be the dominant airborne pollen families at the Delhi site since it was the peak growing season for grasses and weeds. The overall range for total pollen was highest in Rishikesh (300-500 pollen counts) than in Delhi and Kolkata. Among meteorology, rain, temperature, and wind were significantly correlated with bihourly pollen counts with p value < 0.05. Since the cities chosen for the analysis differ in pollution levels, the insights provide a better understanding of pollution and pollen effects.  The study also reflects upon a less explored method of airborne pollen collection, further adding meteorology effects on pollen to the research database. The results will be used to develop prediction model for grass pollen using variables like vegetation and meteorology.

Further work will be assessing pollen counts with respiratory health outcomes. The study’s objective is to provide valuable insights that can benefit to the policy makers, health care workers, scientist community and potentially help in reducing health burden of the country along with providing quality life for susceptible citizens.

How to cite: Dhankhar, A., Dey, S., J Osborne, N., and Darssan, D.: Estimating pollen profiles and assessing relationships with meteorology, air pollutants and vegetation in three cities of India, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-779, https://doi.org/10.5194/egusphere-egu24-779, 2024.

Bioaerosols, or aerosol particles of biological origin, have been found to represent a significant mass fraction of atmospheric particulate matter (PM) and organic carbon (OC). These particles are larger in size (up to 100 µm) than most anthropogenic aerosols but are lighter and thus can be transported over long distances, affecting atmospheric processes and cloud physics (i.e., act as cloud condensation nuclei). Moreover, climate change is expected to increase pollen number concentrations (~21%) as well as pollen season length (+21 days) across North America. So far, only a few studies have been conducted on the chemical composition of bioaerosols and their behavior under atmospheric conditions. The goal of this research was to characterize the chemical composition of bioaerosols using multiple analytical techniques, such as Proton Nuclear Magnetic Resonance Spectroscopy (¹H-NMR), Gas Chromatography-Mass Spectrometry (GC-MS), and Ultra-High Performance Liquid Chromatography-Mass Spectrometry (UPLC-MS), thereby advancing atmospheric aerosol chemistry. Various common bioaerosols, including pollen, algae, fungi, and bacteria, are analyzed, and characterized under controlled laboratory conditions. All samples are analyzed for their chemical composition: saccharides with GC-MS, amino acids and fatty acids with UPLC-MS, and functional groups with ¹H-NMR spectroscopy. The present research is one of the first studies of detailed chemical characterization of bioaerosols with the ¹H-NMR technique, where the ¹H-NMR results are also compared with GC- and UPLC-MS quantitative analyses of individual bioaerosol species.

How to cite: Bahdanovich, P., Axelrod, K., Khlystov, A., and Samburova, V.: Chemical Characterization of Atmospheric Bioaerosols, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2052, https://doi.org/10.5194/egusphere-egu24-2052, 2024.

The Arabian Peninsula is one of the World’s largest dust source regions. It is also affected by natural and anthropogenic pollution of African, Asian, and European origin. As the Arabian Peninsula is highly under-sampled, we have since 2012 established and maintained aerosol monitoring sites at King Abdullah University of Science and Technology (KAUST), as well as in the North-Western part of the Arabian Peninsula, and the Red Sea coast. The sites incorporate the following instrumentation. Two CIMEL sun photometers operational since 2012 as a part of the NASA Aerosol Robotic NETwork (AERONET), providing aerosol optical depth (AOD) and aerosol parameters, reporting data to the NASA Goddard website (http://aeronet.gsfc.nasa.gov/cgi-bin/type_piece_of_map_opera_v2_new). The AOD distribution over the Red Sea is measured during KAUST Red Sea cruises using a hand-held sun photometer (Microtops II). The data are reported to the NASA Maritime Network (http://aeronet.gsfc.nasa.gov/new_web/maritime_aerosol_network.html). Vertical Distribution of aerosols is sampled using the Micro Pulse Lidar (MPL) operating as a part of the NASA MPLNET (http://kimura.gsfc.nasa.gov/site--‐page?site=Kaust). We measure aerosol deposition rates on a monthly basis using passive samplers in different several locations (KAUST, 2015-2023; Al Wajh Lagoon, 2021-2022; DUBA & Tabuk,2022 -2023) and conducted a mineralogical analysis of deposited aerosols by X-ray diffractometry (XRD) and measured particle size distributions using Mastersizer3000.

Our objective in this study is to conduct an in-depth analysis of the combined effects of natural and anthropogenic pollution on air quality, climate, and application of renewable energy across the Arabian Peninsula, providing a scientific foundation for model calibration in this region. Here we report on the data sets collected in 2012- 2023:

• KAUST campus site: Six dust deposition samplers, AERONET, MPL
• Al Wajh Lagoon site: Nine dust deposition samplers
• Duba site: Two dust deposition samplers
• Tabuk site: Two dust deposition samplers

In our group’s research at KAUST, these data sets, in combination with the available satellite observations, were integrated into the meteorology-chemistry-aerosol model, WRF-Chem, to quantify the aerosol environmental impacts and support environmental decision-making in the region.

How to cite: Shevchenko, I., Stenchikov, G., and Engelbrecht, J.: Long-term Aerosol Monitoring at the Western Arabian Peninsula and Red Sea Coast, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2447, https://doi.org/10.5194/egusphere-egu24-2447, 2024.

A massive ecological restoration program has been implemented in northern China with the aim of protecting the Beijing-Tianjin-Hebei the metropolitan area of eastern China from dust events. However, some current studies have cast doubt on the efficacy of such ecological restoration projects, partly due to the constraint of available water in northern China, leading to poor survival rates of planted trees in semiarid regions (15%). In this study, using a logical framework combining statistical analysis, partial least-squares path model analysis, and a regional climate model (RegCM) simulation with multisource dust indicators, we found that there was a reduction of dust in northern China that was synchronous with the increase in vegetation growth after ecological restoration. In contrast to previous reports of a decrease in wind speed due to ecological restoration, this study found that the increase in vegetation had an insignificant impact on local wind speed (p = 0.30). Instead, ecological restoration mainly reduced the sand emission in the steppe areas by improving the soil conditions of the underlying surface and hence contributed 15% of the reduction of dust events in the BeijingTianjin-Hebei metropolitan area through dust transmission (p = 0.002). The effect of ecological restoration in the northern steppe on dust reduction in the northeastern metropolitan area of China should not be overstated.

How to cite: Zhou, C. and Feng, X.: The Regional Impact of Ecological Restoration in the Arid Steppe on Dust Reduction over the Metropolitan Area in Northeastern China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7325, https://doi.org/10.5194/egusphere-egu24-7325, 2024.

Bioaerosols are ubiquitous airborne microorganisms comprised of bacteria, fungi, pollen, virus and their constituents. Fungi have been associated with negative health effects ranging in severity from allergic reactions to asthma and serious infection, where susceptible individuals are at greater risk of life-threatening health outcomes resulting from exposure. While airborne fungi are abundant, they are poorly characterized due to the low temporal resolution of traditional offline sampling methods, limiting our understanding of key emission drivers in critical micro-environments and their impacts on air quality.

There is a critical need to better characterize background fungal aerosol concentrations to build baselines to explore exposure assessment. Here we investigate the utility of emerging real-time detection methods in conjunction with offline sampling during a two-week pilot study to characterize the outdoor concentrations of key aeroallergenic fungi at high time resolution.

A Multiparameter Bioaerosol Spectrometer (MBS) was deployed at UKHSA Chilton alongside a Burkard sampler during August 2022; The MBS is a biofluorescence spectrometer that classifies and quantifies bioaerosols on a single particle basis via their autofluorescent signatures, allowing for fungal aerosol concentrations to be derived at 5-minute time resolution; Next Generation Sequencing (NGS) was performed on daily integrated Burkard samples to provide broader fungal compositional context. Meteorological data was also recorded.

Clear diurnal behaviour in Cladosporium- and Penicillium-like aerosol was observed with the MBS, with maximums occurring in the late afternoon and early morning respectively. These characteristic emission features would not be evident from sample integrations typical of offline sampling. Comparison to the NGS bioinformatics is ongoing.

We demonstrate for the first time the utility of a complimentary real-time and offline NGS dual approach to gain deeper insights into fungal spore emissions. We suggest that this approach shows promise for routine fungi monitoring to assess impacts on public health.

How to cite: Crawford, I., Douglas, P., Macchiarulo, S., and Marczylo, E.: Assessing fungal spore health impacts with real-time detection technologies, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8946, https://doi.org/10.5194/egusphere-egu24-8946, 2024.

The long-range transport of bioaerosols by dust events significantly impacts ecological and meteorological networks of the atmosphere, biosphere and anthroposphere. Bioaerosols not only cause significant public health risks, but also act as efficient ice nuclei for inducing cloud formation and precipitation in the hydrological cycle. To establish risk management for bioaerosol impacts on the Earth system, a large-scale investigation of bioaerosols must be performed under different environmental conditions. For this purpose, a Dust-Bioaerosol (DuBi) field campaign was conducted, to investigate the distribution of bioaerosols by collecting ~ 950 samples at 39 sites across East Asia from 2016 to 2021. Concentrations and community structures of bioaerosols were further analyzed using fluorescence microscopic observations and high-throughput DNA sequencing, and these factors were compared to environmental factors, such as PM₁₀ and aridity. The results indicated that microbial concentrations at dryland sites were statistically higher than those at humid sites, while the microbe to total particle ratio was statistically lower in drylands than in humid regions. Microbial cells per microgram of PM₁₀ decreased when PM₁₀ increased. The proportion of airborne particles at each site did not vary substantially with season. The richness and diversity of airborne bacteria were significantly higher in drylands than in semiarid regions, while the community structures were stable among all sampling sites. The DuBi field campaign helps a better understanding of bioaerosol characteristics variations along dust transport pathway in East Asia and the changes of bioaerosols under the trend of climate warming, supporting the efforts to reduce public health risks.

How to cite: Huang, Z., Dong, Q., Xue, F., Yu, X., Gu, Q., Bi, J., Shi, J., Zhou, T., and Huang, J.: Large-scale Dust-Bioaerosol field observations in East Asia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2775, https://doi.org/10.5194/egusphere-egu24-2775, 2024.

How to cite: Vovk, T., Kryza, M., Tomczyk, S., Malkiewicz, M., Lipiński, P., and Werner, M.: Prediction of airborne allergenic pollen concentrations with machine learning  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9473, https://doi.org/10.5194/egusphere-egu24-9473, 2024.

Dust events over East Asia carry bioaerosols, such as bacteria, fungi, pollen, and plant-animal cell debris, as well as mineral and sea salt. The long-distance dispersion of bioaerosols have possibilities to damage human health due to pathogenic diseases and allergy induction. The microbial communities and biological components in bioaerosols have been investigated using offline analysis, such as DNA sequencing and chromatograph mass-spectrometry, but the contrast of offline databases are insufficiently used for establishing of bioaerosol models offline with chemical and physical database.

Recently, wideband integrated bioaerosol sensors (WIBSs), which detecting autofluorescence emitted from amino acids, proteins, and coenzymes, is focused as online analysis of bioaerosols. However, during the WIBSs monitoring, the interference from other types of fluorescent particles (e.g. polycyclic aromatic hydrocarbons) hardly identify the biological molecular species in bioaerosols. Here, for identifying the bioaerosol composition detected by the WIBSs, the bioaerosol surveys during Asian dust events at Osaka city, Japan, were performed by combining online (WIBS) and offline (DNA-sequencing and microscopic observation) techniques. The comparisons between online and offline data revealed that some types of fluorescent spectrum can determine the concentrations of pollen and fungal cells, which vary in correspondence to dust events as well as seasonal changes and wind directions.

How to cite: Maki, T., Sano, I., Mizuno, H., Gallagher, M., Zhang, H., Crawford, I., Song, C., and Topping, D.: Variation in fluorescent biological aerosol particles over the urban area during Asian dust events, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12736, https://doi.org/10.5194/egusphere-egu24-12736, 2024.

Phosphorus (P) is a key macronutrient vital for all organisms, and it undergoes redistribution between terrestrial and oceanic systems through processes such as atmospheric emission, transport, transformation, and deposition. P is a limiting factor for primary productivity in the east Mediterranean Sea and the atmosphere is an important source of P for the marine ecosystems. Atmospheric P is present as both organic and inorganic species in dissolved and particulate forms and originates from both natural and anthropogenic sources. However, its sources remain uncertain since observational data show that the prevailing fraction of soluble, bioavailable, atmospheric P cannot be attributed to desert dust. Bioaerosols have been proposed as important carriers of nutrients and especially of bioavailable P to the marine ecosystems, potentially contributing to the missing sources of atmospheric P in the Mediterranean. In this study, a large number (234) of ambient PM_2.5 24-h samples that were collected over a multi-yearlong sampling campaign (Dec. 2018 – Jul. 2021) conducted in Athens, one of the largest urban centres in south eastern Mediterranean, were analysed for total phosphorus (TP). In addition to P, chemical components, such as saccharides that are used as proxies of bioaerosols, but also organic carbon (OC), elemental carbon (EC), water-soluble OC, major inorganic anions and cations, elements of crustal origin and trace elements were determined. Preliminary results show the highest concentrations of TP and organic phosphorus (OP) in spring. Inorganic phosphorus exhibits similar levels throughout the seasons, with a small increase in spring. The observed concentrations of anhydro sugars were higher in winter and autumn than in summer due to biomass burning processes, while primary sugars and sugar alcohols indicative of bioaerosols increased throughout the growing season, peaking in spring as found also for total phosphorus concentrations. Positive Matrix Factorization analysis (PMF) is employed to identify the individual sources that affected the air samples and in particular P. Thus, the fraction of P in aerosols attributed to bioaerosol has been estimated. Aerosol sampling has been performed in the frame of the ERC PyroTRACH grant #726165. This work has been supported by the HFRI grant # 4050 BIOCAN.

How to cite: Papoutsidaki, K., Tsiodra, I., Grivas, G., Bougiatioti, A., Oikonomou, K., Kozonaki, F. A., Tavernaraki, K., Tsagkaraki, M., Nenes, A., Mihalopoulos, N., and Kanakidou, M.: Bioaerosol’s contribution to the atmospheric Phosphorus in Athens, Greece, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15716, https://doi.org/10.5194/egusphere-egu24-15716, 2024.

Atmospheric dust from the North Africa, the largest and most persistently active dust source over the world, spreads widely in the Northern Hemisphere and plays essential roles in the Earth environment evolution. During June 7^th-24^th 2020, an extremely strong dust occurred with its westward spreading modulated by the North Atlantic Oscillation (NAO), and its eastward spreading regulated by European blocking, ultimately resulting in the circum-global transport of African dust. The Mediterranean low pressure linked to the European blocking dipole was the key to facilitating the eastward transport of dust. This record-breaking African dust episode caused a notable diurnal precipitation decrease of 0.98 mm day^-1 over northeastern India and decrease of 1.55 mm day^-1 over central North America, which was ascribed to the effect of dust-induced radiative heating on large-scale circulation. It triggered Rossby wave train and caused an anomalous high pressure over northeastern India, which weakened the India summer monsoon and consequently inhibited the occurrence of precipitation. Dust-induced radiative heating also supported the stability in the anomalous warm high over North America, further repressing import of moisture from Atlantic. Ambient moisture and atmospheric instability also presented consistent variation over North America and India characterized as strengthen descending motion and sharply reduced moist convection. This study reports, for the first time, the strong modulation of regional circulation by circum-globally transported African dust especially in Asia and North America. The new aspects on the unexpected consequences to moisture convection indicate broader roles that the dust may play in the global climate change.

How to cite: Hongru, B., Siyu, C., and Daizhou, Z.: The Circum-global Transport of Massive African Dust and its Impacts on the Regional Circulation in Remote Atmosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5121, https://doi.org/10.5194/egusphere-egu24-5121, 2024.

Bioaerosol is generally defined as solid airborne particles of biological origin suspended in the gaseous medium ubiquitously with an aerodynamic diameter of up to 100 µm. They can either be naturally released from the biosphere to the atmosphere or are released due to human activities. Here, we present the results of several experiments, performed inside a confined and controlled artificial environment, such as the Atmospheric Simulation Chamber, providing valuable information on bio-aerosol viability, dispersion, and impact. At ChAMBRe (Chamber for Aerosol Modelling and Bio-aerosol Research), managed by INFN at the Physics Department of the University of Genoa, Italy, the research on bioaerosol is focused on the investigation of the airborne bacteria behavior in different atmospheric and air quality conditions (Massabò et al., 2018). A multi-step protocol was developed (Vernocchi et al, 2023) and thoroughly tested to cultivate a suitable bacteria population (E. coli, B. subtilis, B. licheniformis, and P. fluorescens). Then, bacteria are nebulized, and injected inside ChAMBRe, where they are exposed to different gas concentration values. The viability variation, due to the pollutant exposure inside ChAMBRe, was determined by monitoring the concentration of viable bacteria. The bacteria survival rate inside ChAMBRe is first evaluated by a set of baseline experiments (clean air condition) and successively exposing the bacterial strands to NO₂ and NO concentration values up to 1200 ppb for both pollutants. A WIBS-NEO instrument measured bacteria total concentration inside ChAMBRe while the viable concentration was determined by active sampling on Petri dishes by an Andersen impactor and then counting the Colonies Forming Units (CFU). In addition, a liquid impinger was used to maintain the integrity of the microorganisms and their physiological state to investigate a sampling strategy to assess viability and simultaneously cultivability, taking into account the VBNC status (viable but not cultivable).  To this end, we present the results of impactor experiments and preliminary assessments with live and dead assays examined by fluorescence microscopy for quantitative and qualitative analysis.

References

Massabò, D., Danelli, S. G., Brotto, P., Comite, A., Costa, C., Di Cesare, A., Doussin, J. F., Ferraro, F., Formenti, P., Gatta, E., Negretti, L., Oliva, M., Parodi, F., Vezzulli, L., and Prati, P.: ChAMBRe: a new atmospheric simulation chamber for aerosol modelling and bio-aerosol research, Atmos. Meas. Tech., 11, 5885–5900, https://doi.org/10.5194/amt-11-5885-2018, 2018.

Vernocchi, V., Abd El, E., Brunoldi, M., Danelli, S. G., Gatta, E., Isolabella, T., Mazzei, F., Parodi, F., Prati, P., and Massabò, D. (2023) Atmos. Meas. Tech., 16, 5479–5493. https://doi.org/10.5194/amt-16-5479-2023, 2023.

How to cite: Gatta, E., Abd El, E., Brunoldi, M., Irfan, M., Isolabella, T., Massabò, D., Mazzei, F., Parodi, F., Prati, P., and Vernocchi, V.: Bioaerosol and Atmospheric Simulation Chamber: first studies on bacteria viability versus NOx concentrations., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11309, https://doi.org/10.5194/egusphere-egu24-11309, 2024.

Tajikistan is located in an arid and semi-arid region, with a dry climate and sparse precipitation and the sandstorms frequently occur in summer. The Shaartuz lidar site (68.0°E, 36.9°N, 274 masl) is located in a basin in southern Tajikistan. It is observed that the dust storms occur in this area are usually lifted to a height of 5-6 km above the ground, which is equivalent to the height of the Pamirs covered with ice and snow. With the effects of complex terrain, there is a possibility of the dust being transported to the Pamirs under the mid-latitude westerly belt. In this work, the two lidar systems located in Shaartuz and Taxian (75.2°E, 37.8°N, 3087 masl) which is in the southeast of the Pamirs are utilized to study the dust event in summer. The significant variations of dust optical properties and vertical distribution can be captured by the two lidar system during June 11th to 15th, 2023. The backward trajectory model and satellite observation are used to verify the transport path of the dust event. WRF-Chem also successfully simulated the transport process of the dust event, and analyzed the spatiotemporal evolution characteristics and the dust effects. These results will help us explore the characteristics of central Asian dust transboundary transport toward Pamirs and its regional climate effects.

How to cite: Dong, Q., Huang, Z., Zhou, T., Wang, Y., Wang, T., Bi, J., Liu, Q., Li, Z., Li, W., Shi, J., Li, Z., Liu, W., Niu, Z., and Song, X.: Transboundary transport of central Asian dust to the Pamirs: measurements and modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4599, https://doi.org/10.5194/egusphere-egu24-4599, 2024.

In this paper, long-term temporal and spatial distribution characteristics of aerosols in arid and semi-arid regions of Eurasia (30° N - 60° N, 25° E - 90° E) from 2001 to 2021 were studied by combining Moderate−resolution Imaging Spectroradiometer (MODIS), Cloud−Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) (2007-2021) and Ozone Monitoring Instrument (OMI) observations.  Aerosol types over Eurasia were studied based on aerosol optical depth (AOD), Ångström exponent (AE), and aerosol single scattering albedo (SSA). The results show that the average AOD (obtained from MODIS) is high in the Taklimakan, Tar, Kizikom, and Syria deserts. Seasonal aerosol concentrations in Xinjiang, Iraq, Iran, Kazakhstan, Uzbekistan, and Turkmenistan were the highest in spring, the second-highest in summer, and the lowest in autumn and winter. Clean marine and mixed aerosols are the primary aerosol types in the Eurasia. The relative contribution of meteorological factors to dust optical depth (DOD) and its long-term variation have been quantified by stepwise regression model. The model results show that the contribution of humidity at 500 hPa (H500) to the change of DOD is 28%, the contribution of wind speed (WS) to the change of DOD is 19%, and the contribution of temperature (T) to the change of DOD is 12%.  The spatial distribution of the correlation coefficient between DOD and meteorological factors is higher under the bare surface compared to complex terrain. This result highlights the sensibility of meteorological factors on the distribution of DOD in the desert. The results presented in is paper are helpful for understanding the interaction between DOD and meteorological factors.

© 2014 xxxxxxxx. Hosting by Elsevier B.V. All rights reserved.

How to cite: Zhang, S. and Detlef, M.: Distribution of aerosol optical depth and possible factors influencing dust optical depth over arid and semi−arid Eurasia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2712, https://doi.org/10.5194/egusphere-egu24-2712, 2024.

East Asian desert is one of the most important dust sources that contribute approximately ~40% of the global annual dust emissions and ~88% of the dust over mainland China and adjacent seas, significantly impacting the regional environment and climate. In the past decade, the frequency of dust storm outbreaks has largely declined in the sources of Asian dust due to the improvement of natural conditions (i.e., weakened surface wind speed, enhanced precipitation, and soil water) and the promotion of vegetation cover caused by afforestation in North China. However, it is still rarely reported how the dust properties after long-range transport in the downstream regions respond to this downtrend. During 2010-2020, we have been conducting routine monitoring of height-resolved dust aerosols with a ground-based polarization lidar in Wuhan (30.5°N, 114.4°E), a mega city in central China. The dust optical depths (DOD) have decreased by 0.011 per year, accounting for ~22% of the decrease rate for local aerosol optical depths (AOD). The dust mass concentration and columnar mass density also have declined by 2.03 μg·m^-3 and 1.97 mg·m^-2 per year, respectively. During spring and winter, a mass of long-range transported dust plumes intrude into Wuhan, with seasonal mean DOD of 0.21 and 0.15, respectively. Dust aerosols in winter are generally located at lower altitudes than in spring, concentrating mainly below 1.0 km. Wintertime dust shows a slightly smaller particle depolarization ratio than spring (0.11 versus 0.14), indicating a weakened nonspherical shape caused by high-level moisture/polluted conditions during winter. The surface PM₁₀ concentration presents a downtrend with a rate of -8.0 μg·m^-3·yr^-1. This study provides the climatology of dust properties over central China, supplementing our understanding of the feedback in the downstream regions to the reduction of dust emissions in the East Asia desert.

How to cite: He, Y., Jing, D., Liu, F., and Yin, Z.: Declining trend of dust aerosols over central China observed with polarization lidar during 2010-2020, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2273, https://doi.org/10.5194/egusphere-egu24-2273, 2024.

A study of the dust emission, transport, and deposition is very important for understanding of the various health and social impacts on the local human population, biogeochemical cycle, and the global environmental change. The entry of dust into the atmosphere results from the occurrence of different scales of dust storms resulting from the multi-scale atmospheric processes ranging from the synoptic to near meso-scales of atmospheric motion. In this context, to find the causes of severe dust storms that occurred in the past over north-west Africa, central-north Africa, and Middle east we did a research work. In that study, significant roles of mountains (e.g., Atlas Mountains, Tibesti Mountains, and Sarwat Mountains) were found. For instances, there were a cross mountain flows that produced a leeside inversion layer, which facilitated for the imbalance of the exit region of the jet streak, prior to the large-scale dust storm; generation of terrain (i.e., mountains)-induced downslope winds in response to the transition of the atmospheric flow from a subcritical to supercritical state leading to dust storms; and generation of Kelvin waves supported by the mountains that were responsible for organizing the dust storms and wide distribution and transportation of dust away from the mountains. Regarding this, it is also hypothesized here that similar kinds of roles of mountains are also found in other geographical regions of the world, such as West/North/Northwest China and Mongolia where dust storms occur in the lee of the mountains, (i.e., Tien Shan/ Gobi Altai Mountains/ Khangai Mountains) and involve the long-range transport of atmospheric particulate matter originating from dryland areas. Such events are affecting large numbers of people and their environment especially in spring season because East Asia is the one of the most densely populated areas of the world. In this scenario, these kinds of studies will also be beneficial for analyses of roles of the synoptic features, and identification of their dynamical characteristics are important for evaluating different synoptic dust regimes and their development. So, for the current study, based on the severity of dust storms some cases of dust storms, which occurred in the lee of the respective mountains of China and Mongolia in the past, are considered.

Keywords: Mountains, Dust Storms, Jet streak, Atmosphere

How to cite: Pokharel, A. K. and Pokharel, A.: Roles of Mountains in Dust Storms , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1412, https://doi.org/10.5194/egusphere-egu24-1412, 2024.