Saharan Dust Records and Its Impact in the European Alps

2021 ◽  
Author(s):  
Marion Greilinger ◽  
Anne Kasper-Giebl
Keyword(s):  
Mineral Dust ◽  
Cloud Condensation Nuclei ◽  
Ice Cores ◽  
Atmospheric Particulate Matter ◽  
Saharan Dust ◽  
Cloud Formation ◽  
Dust Particles ◽  
European Alps ◽  
Airborne Dust ◽  
Dust Events

Mineral dust is one of the main natural sources of atmospheric particulate matter, with the Sahara being one of the most important source regions for the occurrence and deposition of mineral dust in Europe. The occurrence of dust events in the European Alps is documented via measurements of airborne dust and its deposits onto the glaciers. Dust events occur mainly in spring, summer, and early autumn. Dust layers are investigated in ice cores spanning the last millennium as well as in annual snow packs. They strongly affect the overall flux of dust-related compounds (e.g., calcium and magnesium), provide an alkaline input to wet deposition chemistry, and change the microbial abundance and diversity of the snow pack. Still airborne mineral dust particles can act as ice nuclei and cloud condensation nuclei, influencing the formation of cloud droplets and hence cloud formation and precipitation. Dust deposits on the snow lead to a darkening of the surface, referred to as “surface albedo reduction,” which influences the timing of the snowmelt and reduces the annual mass balance of glaciers, showing a direct link to glacier retreat as observed presently in a warming climate.

A modeling insight into the transport of large dust particles

2021 ◽  
Author(s):  
Eleni Drakaki ◽  
Alexandra Tsekeri ◽  
Vasillis Amiridis ◽  
Stavros Solomos ◽  
Antonis Gkikas ◽  
...  
Keyword(s):  
Size Distribution ◽  
Mineral Dust ◽  
Saharan Dust ◽  
Cloud Formation ◽  
Dust Particles ◽  
Negative Effects ◽  
Airborne Dust ◽  
Horizon 2020 ◽  
Research And Innovation ◽  
The Impact

<p>Mineral dust is an important component of the climate system, affecting radiation, cloud formation, biogeochemical cycles, as well as having negative effects on solar energy budget and human health. All these processes are affected from the size of the particles which is significantly underestimated by the Earth System Models. Here, we present results from a first attempt to modify the size distribution parameterizations in the GOCART-AFWA dust scheme of WRF - Chem, by including the large dust particles with diameters greater than 20 µm to describe the mineral dust cycle. The parameterization is based on Saharan dust observational datasets from FENNEC and SAMUM campaigns. We investigate the impact of the extended size distribution on the overall transported dust load and also the impact of particle settling considerations in deposition rates. The model results are compared with airborne dust measurements from AER-D campaign. In order to achieve the best agreement with the observations, an artificial force that counteracts gravity approximately by 80% for the large particles is needed, indicating the presence of one or more under-represented physical processes in the model.</p><p><strong>Acknowledgment:</strong> 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. </p>

scholarly journals Impact of mineral dust on cloud formation in a Saharan outflow region

2011 ◽  
Vol 11 (12) ◽  
pp. 32363-32390 ◽  
Author(s):  
L. Smoydzin ◽  
A. Teller ◽  
H. Tost ◽  
M. Fnais ◽  
J. Lelieveld
Keyword(s):  
Radiative Forcing ◽  
Mineral Dust ◽  
Eastern Mediterranean ◽  
Cloud Condensation Nuclei ◽  
Coupled Model ◽  
Cloud Formation ◽  
Dust Particles ◽  
Ice Nuclei ◽  
Outflow Region ◽  
The Impact

Abstract. We present a numerical modelling study investigating the impact of mineral dust on cloud formation over the Eastern Mediterranean for two case studies: (i) 25 September 2008 and (ii) 28/29 January 2003. On both days dust plumes crossed the Mediterranean and interacted with clouds forming along frontal systems. For our investigation we used the fully online coupled model WRF-chem. The results show that increased aerosol concentrations due to the presence of mineral dust can enhance the formation of ice crystals. This leads to slight shifts of the spatial and temporal precipitation patterns compared to scenarios where dust was not considered to act as ice nuclei. However, the total amount of precipitation did not change significantly. The only exception occurred when dust entered into an area of orographic ascent, causing glaciation of the clouds, leading to a local enhancement of rainfall. The impact of dust particles acting as giant cloud condensation nuclei on precipitation formation was found to be small. Based on our simulations the contribution of dust to the CCN population is potentially significant only for warm phase clouds. Nevertheless, the dust-induced differences in the microphysical structure of the clouds can contribute to a significant radiative forcing.

Measurements of Saharan Dust in Convective Clouds over the Tropical Eastern Atlantic Ocean*

2015 ◽  
Vol 72 (1) ◽  
pp. 75-81 ◽  
Author(s):  
Cynthia H. Twohy
Keyword(s):  
Mineral Dust ◽  
Cloud Condensation Nuclei ◽  
Saharan Dust ◽  
Dust Particles ◽  
Tropical Storms ◽  
Liquid Droplets ◽  
Particle Type ◽  
Convective Clouds ◽  
Ice Nuclei ◽  
Eastern Atlantic Ocean

Abstract Mineral dust particles have been shown to act as cloud condensation nuclei, and they are known to interact with developing tropical storms over the Atlantic downwind of the Sahara. Once present within liquid droplets, they have the potential to act as freezing ice nuclei and further affect the microphysics, dynamics, and evolution of tropical storms. However, few measurements of mineral dust particles in tropical convective clouds exist. This study indicates that about one-third of droplets sampled in small convective clouds in the tropical eastern Atlantic contained dust particles, and dust was the dominant residual particle type sampled in ice crystals from anvil outflow. However, estimated number and mass concentrations of dust in anvil ice were small compared to the amount of dust available within the Saharan air layer itself.

scholarly journals Impact of mineral dust on cloud formation in a Saharan outflow region

2012 ◽  
Vol 12 (23) ◽  
pp. 11383-11393 ◽  
Author(s):  
L. Smoydzin ◽  
A. Teller ◽  
H. Tost ◽  
M. Fnais ◽  
J. Lelieveld
Keyword(s):  
Radiative Forcing ◽  
Mineral Dust ◽  
Eastern Mediterranean ◽  
Cloud Condensation Nuclei ◽  
Coupled Model ◽  
Cloud Formation ◽  
Dust Particles ◽  
Ice Nuclei ◽  
Outflow Region ◽  
The Impact

Abstract. We present a numerical modelling study investigating the impact of mineral dust on cloud formation over the Eastern Mediterranean for two case studies: (i) 25 September 2008 and (ii) 28/29 January 2003. In both cases dust plumes crossed the Mediterranean and interacted with clouds forming along frontal systems. For our investigation we used the fully online coupled model WRF-chem. The results show that increased aerosol concentrations due to the presence of mineral dust can enhance the formation of ice crystals. This leads to slight shifts of the spatial and temporal precipitation patterns compared to scenarios where dust was not considered to act as ice nuclei. However, the total amount of precipitation did not change significantly. The only exception occurred when dust entered into an area of orographic ascent, causing glaciation of the clouds, leading to a local enhancement of rainfall. The impact of dust particles acting as giant cloud condensation nuclei on precipitation formation was found to be small. Based on our simulations the contribution of dust to the CCN population is potentially significant only for warm phase clouds. Nevertheless, the dust-induced differences in the microphysical structure of the clouds can contribute to a significant radiative forcing, which is important from a climate perspective.

scholarly journals Saharan dust events in the European Alps: role on snowmelt and geochemical characterization

2018 ◽  
Author(s):  
Biagio Di Mauro ◽  
Roberto Garzonio ◽  
Micol Rossini ◽  
Gianluca Filippa ◽  
Paolo Pogliotti ◽  
...  
Keyword(s):  
Digital Images ◽  
Mineral Dust ◽  
Saharan Dust ◽  
European Alps ◽  
Snow Melt ◽  
Dust Deposition ◽  
Geochemical Characterization ◽  
Melting Dynamics ◽  
Dust Events ◽  
The Impact

Abstract. The input of mineral dust from arid regions impacts snow optical properties. The induced albedo reduction generally alters the melting dynamics of the snowpack, resulting in earlier snowmelt. In this paper, we evaluate the impact of dust depositions on the melting dynamics of snowpack in a high-altitude site (2160 m) in the European Alps (Torgnon, Aosta Valley, Italy) during three hydrological years (2013–2016). These years were characterized by several Saharan dust events that deposited significant amounts of mineral dust in the European Alps. We quantify the shortening of snow season due to dust deposition, by comparing observed snow depths and those simulated with the Crocus model accounting or not for the impact of impurities. The model was ran and tested using meteorological data from an Automated Weather Station. We propose the use of repeated digital images for tracking dust deposition and resurfacing in the snowpack. The good agreement between model prediction and digital images allowed us to propose the use of an RGB index (i.e. snow darkening index, SDI) for monitoring dust on snow using images from a digital camera. We also present a geochemical characterization of dust reaching the Alpine chain during spring in 2014. Elements found in dust were classified as a function of their origin and compared with Saharan sources. A strong enrichment in Fe was observed in snow containing Saharan dust. In our case study, impurities deposited in snow anticipated the disappearance of snow up to 38 days for the 2015/2016 season that was characterized by a strong dust deposition event, out of a total 7 months of typical snow persistence. During the other seasons considered here (2013/2014, and 2014/2015), the advancement in snow melt-out day was 18 and 11 days respectively. We conclude that the effect of the Saharan dust is to anticipate the snow melt-out dates, that is known to have a series of feedback effects: earlier snowmelt can propagate into altered hydrological cycle in the Alps, higher sensitivity to late summer drought, impact on vegetation phenology and carbon uptakes from the atmosphere.

scholarly journals Saharan dust events in the European Alps: role in snowmelt and geochemical characterization

2019 ◽  
Vol 13 (4) ◽  
pp. 1147-1165 ◽  
Author(s):  
Biagio Di Mauro ◽  
Roberto Garzonio ◽  
Micol Rossini ◽  
Gianluca Filippa ◽  
Paolo Pogliotti ◽  
...  
Keyword(s):  
Digital Images ◽  
Mineral Dust ◽  
Saharan Dust ◽  
Future Research ◽  
European Alps ◽  
Dust Deposition ◽  
Geochemical Characterization ◽  
Melting Dynamics ◽  
Dust Events ◽  
The Impact

Abstract. The input of mineral dust from arid regions impacts snow optical properties. The induced albedo reduction generally alters the melting dynamics of the snowpack, resulting in earlier snowmelt. In this paper, we evaluate the impact of dust depositions on the melting dynamics of snowpack at a high-elevation site (2160 m) in the European Alps (Torgnon, Aosta Valley, Italy) during three hydrological years (2013–2016). These years were characterized by several Saharan dust events that deposited significant amounts of mineral dust in the European Alps. We quantify the shortening of the snow season due to dust deposition by comparing observed snow depths and those simulated with the Crocus model accounting, or not, for the impact of impurities. The model was run and tested using meteorological data from an automated weather station. We propose the use of repeated digital images for tracking dust deposition and resurfacing in the snowpack. The good agreement between model prediction and digital images allowed us to propose the use of an RGB index (i.e. snow darkening index – SDI) for monitoring dust on snow using images from a digital camera. We also present a geochemical characterization of dust reaching the Alpine chain during spring in 2014. Elements found in dust were classified as a function of their origin and compared with Saharan sources. A strong enrichment in Fe was observed in snow containing Saharan dust. In our case study, the comparison between modelling results and observations showed that impurities deposited in snow anticipated the disappearance of snow up to 38 d a out of a total 7 months of typical snow duration. This happened for the season 2015–2016 that was characterized by a strong dust deposition event. During the other seasons considered here (2013–2014 and 2014–2015), the snow melt-out date was 18 and 11 d earlier, respectively. We conclude that the effect of the Saharan dust is expected to reduce snow cover duration through the snow-albedo feedback. This process is known to have a series of further hydrological and phenological feedback effects that should be characterized in future research.

scholarly journals Saharan dust intrusions over the northern Mediterranean region in the frame of EARLINET (2014–2017): Properties and impact in radiative forcing

2020 ◽  
Author(s):  
Ourania Soupiona ◽  
Alexandros Papayannis ◽  
Panagiotis Kokkalis ◽  
Romanos Foskinis ◽  
Guadalupe Sánchez Hernández ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Saharan Dust ◽  
High Spectral Resolution ◽  
Dust Particles ◽  
Airborne Dust ◽  
Geometrical Properties ◽  
Thermal Range ◽  
Lidar Measurements ◽  
Dust Events ◽  
Saharan Dust Intrusions

Abstract. Remote sensing measurements of aerosols using depolarization Raman Lidar systems from 4 EARLINET (European Aerosol research Lidar Network) stations are used for a comprehensive analysis of Saharan dust events over the Mediterranean basin in the period 2014–2017. In this period, we selected to study 51 dust events regarding the geometrical, optical and microphysical properties of dust particles, classifying them and assessing their radiative forcing effect on the atmosphere. From West to East, the stations of Granada, Potenza, Athens and Limassol were selected as representative Mediterranean cities regularly affected by Saharan dust intrusions. Emphasis was given on lidar measurements in the visible (532 nm) and specifically on the consistency of the particle linear depolarization ratio (δp532), the extinction-to-backscatter lidar ratio (LR532) and the Aerosol Optical Thickness (AOT532) within the observed dust layers. We found mean δp532 values of 0.24 ± 0.05, 0.26 ± 0.06, 0.28 ± 0.05 and 0.28 ± 0.04, mean LR532 values of 52 ± 8 sr, 51 ± 9 sr, 52 ± 9 sr and 49 ± 6 sr, and mean AOT532 values of 0.40 ± 0.31, 0.11 ± 0.07, 0.12 ± 0.10 and 0.32 ± 0.17, for Granada, Potenza, Athens and Limassol, respectively. The mean layer thickness values were found to range from ~1700 to ~3400 m. Additionally, based also on a previous aerosol type classification scheme provided by airborne High Spectral Resolution Lidar (HSRL) observations and on air mass backward trajectory analysis, a clustering analysis was performed in order to identify the major mixing aerosol types over the studied area. Furthermore, a synergy of lidar measurements and modeling was used to deeply analyze the solar and thermal radiative forcing of airborne dust. In total, a cooling behavior in the solar range and a significantly lower heating behavior in the thermal range was estimated. Depending on the dust optical and geometrical properties, the load intensity and the solar zenith angle (SZA), the estimated solar radiative forcing values range from −59 to −22 W m−2 at the surface and from −24 to −1 W m−2 at the top of the atmosphere (TOA). Similarly, in the thermal spectral range these values range from +2 to +4 W m−2 for the surface and from +1 to +3 W m−2 for the TOA. Finally, the radiative forcing seems to be inversely proportional to the dust mixing ratio, since higher absolute values are estimated for less mixed dust layers.

scholarly journals Saharan dust and giant quartz particle transport towards Iceland

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
György Varga ◽  
Pavla Dagsson-Walhauserová ◽  
Fruzsina Gresina ◽  
Agusta Helgadottir
Keyword(s):  
Numerical Models ◽  
Saharan Dust ◽  
Atmospheric Environment ◽  
The Arctic ◽  
Dust Particles ◽  
Atmospheric Flow ◽  
Dust Transport ◽  
Strong Winds ◽  
Dust Events ◽  
Local Dust

AbstractMineral dust emissions from Saharan sources have an impact on the atmospheric environment and sedimentary units in distant regions. Here, we present the first systematic observations of long-range Saharan dust transport towards Iceland. Fifteen Saharan dust episodes were identified to have occurred between 2008 and 2020 based on aerosol optical depth data, backward trajectories and numerical models. Icelandic samples from the local dust sources were compared with deposited dust from two severe Saharan dust events in terms of their granulometric and mineralogical characteristics. The episodes were associated with enhanced meridional atmospheric flow patterns driven by unusual meandering jets. Strong winds were able to carry large Saharan quartz particles (> 100 µm) towards Iceland. Our results confirm the atmospheric pathways of Saharan dust towards the Arctic, and identify new northward meridional long-ranged transport of giant dust particles from the Sahara, including the first evidence of their deposition in Iceland as previously predicted by models.

scholarly journals Modelling Atmospheric Mineral Aerosol Chemistry to Predict Heterogeneous Photooxidation of SO<sub>2</sub>

2017 ◽  
Author(s):  
Zechen Yu ◽  
Myoseon Jang ◽  
Jiyeon Park
Keyword(s):  
Mineral Dust ◽  
Uv Light ◽  
Full Range ◽  
Saharan Dust ◽  
Dust Particles ◽  
Oh Radicals ◽  
Desorption Kinetics ◽  
So2 Oxidation ◽  
Photocatalytic Ability ◽  
Sulfate Formation

Abstract. The photocatalytic ability of airborne mineral dust particles is known to heterogeneously promote SO2 oxidation, but prediction of this phenomenon is not fully taken into account by current models. In this study, the Atmospheric Mineral Aerosol Reaction (AMAR) model was developed to capture the influence of air-suspended mineral dust particles on sulfate formation in various environments. In the model, SO2 oxidation proceeds in three phases including the gas phase, the inorganic-salted aqueous phase (non-dust phase), and the dust phase. Dust chemistry is described as the adsorption-desorption kinetics (gas-particle partitioning) of SO2 and NOx. The reaction of adsorbed SO2 on dust particles occurs via two major paths: autoxidation of SO2 in open air and photocatalytic mechanisms under UV light. The kinetic mechanism of autoxidation was first leveraged using controlled indoor chamber data in the presence of Arizona Test Dust (ATD) particles without UV light, and then extended to photochemistry. With UV light, SO2 photooxidation was promoted by surface oxidants (OH radicals) that are generated via the photocatalysis of semiconducting metal oxides (electron–hole theory) of ATD particles. This photocatalytic rate constant was derived from the integration of the combinational product of the dust absorbance spectrum and wave-dependent actinic flux for the full range of wavelengths of the light source. The predicted concentrations of sulfate and nitrate using the AMAR model agreed well with outdoor chamber data that were produced under natural sunlight. For seven consecutive hours of photooxidation of SO2 in an outdoor chamber, dust chemistry at the low NOx level was attributed to 70 % of total sulfate (60 ppb SO2, 290 μg m−3 ATD, and NOx less than 5 ppb). At high NOx (> 50 ppb of NOx with low hydrocarbons), sulfate formation was also greatly promoted by dust chemistry, but it was significantly suppressed by the competition between NO2 and SO2 that both consume the dust-surface oxidants (OH radicals or ozone). The AMAR model, derived in this study with ATD particles, will provide a platform for predicting sulfate formation in the presence of authentic dust particles (e.g. Gobi and Saharan dust).

scholarly journals Saharan dust levels in Greece and received inhalation doses

2008 ◽  
Vol 8 (3) ◽  
pp. 11967-11996 ◽  
Author(s):  
C. Mitsakou ◽  
G. Kallos ◽  
N. Papantoniou ◽  
C. Spyrou ◽  
S. Solomos ◽  
...  
Keyword(s):  
Urban Areas ◽  
Particle Deposition ◽  
Mineral Dust ◽  
Weather Conditions ◽  
Pm10 Concentration ◽  
Saharan Dust ◽  
Dust Particles ◽  
Annual Number ◽  
Human Respiratory Tract ◽  
Dust Transport

Abstract. The desert of Sahara is one of the major sources of mineral dust on Earth, producing around 2×108 tons/yr. Under certain weather conditions, dust particles from Saharan desert get transported over the Mediterranean Sea and most of Europe. The limiting values set by the directive EC/30/1999 of European Union can easily be exceeded by the transport of desert dust particles in all south European areas and especially urban. In this study, the effects of dust transport on air quality in several Greek urban areas are quantified. PM10 concentration values from stationary monitoring stations are compared to dust concentrations for the 4-year period 2003–2006. The dust concentration values in the Greek areas were estimated by the SKIRON modelling system coupled with embedded algorithms describing the dust cycle. The mean annual dust contribution to daily-averaged PM10 concentration values was found to be around or even greater than 10% in the urban areas throughout the years examined. Natural dust transport may contribute by much more than 20% to the annual number of exceedances – PM10 values greater than EU limits – depending on the specific monitoring location. In a second stage of the study, the inhaled lung dose received by the residents in various Greek locations is calculated. The particle deposition efficiency of mineral dust at the different parts of the human respiratory tract is determined by applying a lung dosimetry numerical model, which incorporates inhalation dynamics and aerosol physical processes. The inhalation dose from mineral dust particles was greater in the upper respiratory system (extrathoracic region) and less significant in the lungs, especially in the sensitive alveolar region. However, in cases of dust episodes, the amounts of mineral dust deposited along the human lung are comparable to those received during exposure in heavily polluted urban or smoking areas.

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