scholarly journals Seasonal changes of Sahara desert dust transport over Balkans

2021 ◽  
Vol 33 ◽  
pp. 76-86
Author(s):  
Maria Dimitrova
Keyword(s):  
Sahara Desert ◽  
Satellite Measurements ◽  
Seasonal Behavior ◽  
Dust Transport ◽  
The Balkans ◽  
Desert Dust ◽  
Space Instruments ◽  
Area Of Interest ◽  
Aerosol Index ◽  
Different Sources

This article presents an investigation of seasonal behavior of Sahara desert dust transport over the Balkans. The data used is satellite measurements of monthly averaged Absorption Aerosol Index (AAI) value. The researched period is from June 1995 till the end of 2019. The data used is from four different space instruments onboard five satellites. The area of interest is a rectangle with corners 23 E 43 N and 24 E 35 N. The data from different sources is compared and discussed.

Modelling an exceptional desert dust transport toward Portugal on February 2017

2020 ◽  
Author(s):  
Maria João Costa ◽  
Flavio Couto ◽  
Eduardo Cardoso ◽  
Rui Salgado ◽  
Juan Luis Guerrero-Rascado
Keyword(s):  
Iberian Peninsula ◽  
Atmospheric Circulation ◽  
Dust Emission ◽  
Horizontal Resolution ◽  
Sahara Desert ◽  
Dust Transport ◽  
Western Sahara ◽  
Orographic Effects ◽  
Desert Dust ◽  
The North

<p>The terrain surrounding the Sahara desert is formed by some mountains ranges, as the Atlas mountain system in the northern edge of the desert and the Hoggar Mountains in Southern Algeria. Such orography, jointly with atmospheric circulation, plays an important role in the mobilization and transport of desert dust over medium and large distances. This study explores the interaction between complex terrain and atmospheric circulation in order to better understand an exceptional desert dust outbreak affecting Portugal in February 2017. The Meso-NH model is able to represent the atmospheric motions in different scales, and has been implemented with a rather complete parametrization package of physical processes in the atmosphere. The capability of the model to simulate dust emission is also explored. The on-line dust emission parametrization type is taken from the distribution of emitted dust of SURFEX with no need to use chemistry to activate dusts. A set of two simulations was performed for the period between 16 February at 0000 UTC to 24 February 1200 UTC, with the Meso-NH model configured in a single domain at 10 km horizontal resolution and 300x360 grid points. The experiments were defined as a) control experiment (CTRL), and b) dust experiment (DUST). From the large domain simulations, it was possible to assess the source of dust and its mobilization over Western Sahara desert, namely over the Northern part of Mauritania and Mali and Eastern part of Algeria. The formation of a cyclonic circulation at the surface favoured the dust uplifting. Such a surface low merged with a cut-off low that moved southward over the Iberian Peninsula and remained centred in the north of Morocco. Such pattern intensified the northward flow found at 700 hPa toward the Atlas Mountains range, inducing the dust transport above 3 km altitude. As expected, the simulations showed the ability to assess important details about the atmospheric circulation not resolved by low density of observations over the domain considered. Furthermore, the simulations were able to show the way that the atmospheric ingredients were brought together to produce the exceptional transport of desert dust toward Portugal. The orographic effects playing an important role in dust mobilization (convergence and cyclogenesis at the surface) and atmospheric circulation to the maintenance of the dust transport have been highlighted. Such event were responsible for the transport of high amount of dust toward the Iberian Peninsula.</p>

scholarly journals Three-dimensional evolution of Saharan dust transport towards Europe based on a 9-year EARLINET-optimized CALIPSO dataset

2017 ◽  
Vol 17 (9) ◽  
pp. 5893-5919 ◽  
Author(s):  
Eleni Marinou ◽  
Vassilis Amiridis ◽  
Ioannis Binietoglou ◽  
Athanasios Tsikerdekis ◽  
Stavros Solomos ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Three Dimensional ◽  
Satellite Observation ◽  
Saharan Dust ◽  
Winter Period ◽  
Dust Transport ◽  
The Balkans ◽  
Potential Applications ◽  
The Mediterranean ◽  
Dust Evolution

Abstract. In this study we use a new dust product developed using CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) observations and EARLINET (European Aerosol Research Lidar Network) measurements and methods to provide a 3-D multiyear analysis on the evolution of Saharan dust over North Africa and Europe. The product uses a CALIPSO L2 backscatter product corrected with a depolarization-based method to separate pure dust in external aerosol mixtures and a Saharan dust lidar ratio (LR) based on long-term EARLINET measurements to calculate the dust extinction profiles. The methodology is applied on a 9-year CALIPSO dataset (2007–2015) and the results are analyzed here to reveal for the first time the 3-D dust evolution and the seasonal patterns of dust over its transportation paths from the Sahara towards the Mediterranean and Continental Europe. During spring, the spatial distribution of dust shows a uniform pattern over the Sahara desert. The dust transport over the Mediterranean Sea results in mean dust optical depth (DOD) values up to 0.1. During summer, the dust activity is mostly shifted to the western part of the desert where mean DOD near the source is up to 0.6. Elevated dust plumes with mean extinction values between 10 and 75 Mm−1 are observed throughout the year at various heights between 2 and 6 km, extending up to latitudes of 40° N. Dust advection is identified even at latitudes of about 60° N, but this is due to rare events of episodic nature. Dust plumes of high DOD are also observed above the Balkans during the winter period and above northwest Europe during autumn at heights between 2 and 4 km, reaching mean extinction values up to 50 Mm−1. The dataset is considered unique with respect to its potential applications, including the evaluation of dust transport models and the estimation of cloud condensation nuclei (CCN) and ice nuclei (IN) concentration profiles. Finally, the product can be used to study dust dynamics during transportation, since it is capable of revealing even fine dynamical features such as the particle uplifting and deposition on European mountainous ridges such as the Alps and Carpathian Mountains.

scholarly journals Interpretation of FRESCO cloud retrievals in case of absorbing aerosol events

2012 ◽  
Vol 12 (19) ◽  
pp. 9057-9077 ◽  
Author(s):  
P. Wang ◽  
O. N. E. Tuinder ◽  
L. G. Tilstra ◽  
M. de Graaf ◽  
P. Stammes
Keyword(s):  
Trace Gas ◽  
Aerosol Layer ◽  
Satellite Measurements ◽  
Dominant Effect ◽  
Cloud Data ◽  
Retrieval Scheme ◽  
Absorbing Aerosols ◽  
Aerosol Effects ◽  
Aerosol Index ◽  
Aerosol Types

Abstract. Cloud and aerosol information is needed in trace gas retrievals from satellite measurements. The Fast REtrieval Scheme for Clouds from the Oxygen A band (FRESCO) cloud algorithm employs reflectance spectra of the O2 A band around 760 nm to derive cloud pressure and effective cloud fraction. In general, clouds contribute more to the O2 A band reflectance than aerosols. Therefore, the FRESCO algorithm does not correct for aerosol effects in the retrievals and attributes the retrieved cloud information entirely to the presence of clouds, and not to aerosols. For events with high aerosol loading, aerosols may have a dominant effect, especially for almost cloud free scenes. We have analysed FRESCO cloud data and Absorbing Aerosol Index (AAI) data from the Global Ozone Monitoring Experiment (GOME-2) instrument on the Metop-A satellite for events with typical absorbing aerosol types, such as volcanic ash, desert dust and smoke. We find that the FRESCO effective cloud fractions are correlated with the AAI data for these absorbing aerosol events and that the FRESCO cloud pressure contains information on aerosol layer pressure. For cloud free scenes, the derived FRESCO cloud pressure is close to the aerosol layer pressure, especially for optically thick aerosol layers. For cloudy scenes, if the strongly absorbing aerosols are located above the clouds, then the retrieved FRESCO cloud pressure may represent the height of the aerosol layer rather than the height of the clouds. Combining FRESCO and AAI data, an estimate for the aerosol layer pressure can be given.

scholarly journals Aerosols in the CALIOPE air quality modelling system: evaluation and analysis of PM levels, optical depths and chemical composition over Europe

2012 ◽  
Vol 12 (7) ◽  
pp. 3363-3392 ◽  
Author(s):  
S. Basart ◽  
M. T. Pay ◽  
O. Jorba ◽  
C. Pérez ◽  
P. Jiménez-Guerrero ◽  
...  
Keyword(s):  
Air Quality ◽  
Fine Fraction ◽  
Ground Level ◽  
Air Quality Modelling ◽  
Aerosol Composition ◽  
Dust Transport ◽  
Desert Dust ◽  
Po Valley ◽  
Limit Value ◽  
Modelling System

Abstract. The CALIOPE air quality modelling system is developed and applied to Europe with high spatial resolution (12 km × 12 km). The modelled daily-to-seasonal aerosol variability over Europe in 2004 is evaluated and analysed. Aerosols are estimated from two models, CMAQv4.5 (AERO4) and BSC-DREAM8b. CMAQv4.5 calculates biogenic, anthropogenic and sea salt aerosol and BSC-DREAM8b provides the natural mineral dust contribution from North African deserts. For the evaluation, we use daily PM10, PM2.5 and aerosol components data from 55 stations of the EMEP/CREATE network and total, coarse and fine aerosol optical depth (AOD) data from 35 stations of the AERONET sun photometer network. Annual correlations between modelled and observed values for PM10 and PM2.5 are 0.55 and 0.47, respectively. Correlations for total, coarse and fine AOD are 0.51, 0.63, and 0.53, respectively. The higher correlations of the PM10 and the coarse mode AOD are largely due to the accurate representation of the African dust influence in the forecasting system. Overall PM and AOD levels are underestimated. The evaluation of the aerosol components highlights underestimations in the fine fraction of carbonaceous matter (EC and OC) and secondary inorganic aerosols (SIA; i.e. nitrate, sulphate and ammonium). The scores of the bulk parameters are significantly improved after applying a simple model bias correction based on the observed aerosol composition. The simulated PM10 and AOD present maximum values over the industrialized and populated Po Valley and Benelux regions. SIA are dominant in the fine fraction representing up to 80% of the aerosol budget in latitudes north of 40° N. In southern Europe, high PM10 and AOD are linked to the desert dust transport from the Sahara which contributes up to 40% of the aerosol budget. Maximum seasonal ground-level concentrations (PM10 > 30 μg m−3) are found between spring and early autumn. We estimate that desert dust causes daily exceedances of the PM10 European air quality limit value (50 μg m−3) in large areas south of 45° N with more than 75 exceedances per year in the southernmost regions.

scholarly journals Novel SO<sub>2</sub> spectral evaluation scheme using the 360–390 nm wavelength range

2010 ◽  
Vol 3 (4) ◽  
pp. 879-891 ◽  
Author(s):  
N. Bobrowski ◽  
C. Kern ◽  
U. Platt ◽  
C. Hörmann ◽  
T. Wagner
Keyword(s):  
Spectroscopic Method ◽  
Wavelength Region ◽  
Optical Absorption Spectroscopy ◽  
Satellite Measurements ◽  
Evaluation Scheme ◽  
Area Of Interest ◽  
Standard Tool ◽  
Spectral Evaluation ◽  
Emission Fluxes

Abstract. Differential Optical Absorption Spectroscopy (DOAS) is a well established spectroscopic method to determine trace gases in the atmosphere. During the last decade, passive DOAS, which uses solar radiation scattered in the atmosphere as a light source, has become a standard tool to determine SO2 column densities and emission fluxes from volcanoes and other large sources by ground based as well as satellite measurements. For the determination of SO2 column densities, the structured absorption of the molecule in the 300–330 nm region (due to the A1B1 ← X1A1 transition) is used. However, there are several problems limiting the accuracy of the technique in this particular application. Here we propose to use an alternative wavelength region (360–390 nm) due to the spin-forbidden a3B2 ← X1A1 transition for the DOAS evaluation of SO2 in conditions where high SO2 column densities prevail. We show this range to have considerable advantages in such cases, in particular when the particle content of the plume is high and when measurements are performed at large distances from the area of interest.

scholarly journals Characterisation of a stratospheric sulfate plume from the Nabro volcano using a combination of passive satellite measurements in nadir and limb geometry

2014 ◽  
Vol 14 (15) ◽  
pp. 8149-8163 ◽  
Author(s):  
M. J. M. Penning de Vries ◽  
S. Dörner ◽  
J. Puķīte ◽  
C. Hörmann ◽  
M. D. Fromm ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Single Scattering ◽  
Sulfate Aerosols ◽  
Viewing Angle ◽  
Satellite Measurements ◽  
Lower Altitude ◽  
Angle Dependence ◽  
Ground Based Lidar ◽  
Aerosol Index ◽  
Aerosol Plume

Abstract. The eruption of the Nabro volcano (Eritrea), which started on 12 June 2011, caused the introduction of large quantities of SO2 into the lower stratosphere. The subsequently formed sulfate aerosols could be detected for several months following the eruption. It is generally assumed that the formation of sulfate aerosols in the stratosphere is a relatively slow process, but in plumes from explosive eruptions significant amounts of aerosols have been seen to form within a few hours. We show that sulfate aerosols were present in the lower stratosphere within hours of the onset of the eruption of Nabro. Evidence comes from nadir UV Aerosol Index (UVAI) and SO2 measurements by SCIAMACHY, GOME-2 and OMI, and limb aerosol measurements by SCIAMACHY. The sulfate plume displays negative UVAI in the western part of OMI's swath and positive UVAI in the eastern part – an effect that is due to the strong viewing angle dependence of UVAI and can only be caused by a high-altitude (>11 km), non-absorbing (single-scattering albedo >0.97) aerosol plume. For the retrieval of the aerosol profile from limb measurements, the horizontal dimensions and the position of the aerosol plume need to be taken into account, otherwise both extinction and layer height may be underestimated appreciably. By combining nadir SO2 column density and UVAI with limb aerosol profiles, a stratospheric plume from Nabro could be tracked from 13 to 17 June, before the plumes from later, lower-altitude explosions started interfering with the signal. Our findings are in agreement with ground-based lidar and sun-photometer data from an MPLNET/AERONET station in Israel and with data from the satellite-borne CALIOP lidar.

Impact of long-range desert dust transport on hydrometeor formation over coastal East Asia

2016 ◽  
Vol 34 (1) ◽  
pp. 101-115 ◽  
Author(s):  
Zhenxi Zhang ◽  
Wen Zhou ◽  
Mark Wenig ◽  
Liangui Yang
Keyword(s):  
East Asia ◽  
Long Range ◽  
Dust Transport ◽  
Desert Dust

scholarly journals Temporal and spectral variation of desert dust and biomass burning aerosol scenes from 1995–2000 using GOME

2006 ◽  
Vol 6 (1) ◽  
pp. 1321-1353 ◽  
Author(s):  
M. de Graaf ◽  
P. Stammes ◽  
I. Aben
Keyword(s):  
Biomass Burning ◽  
Near Infrared ◽  
Spectral Variation ◽  
Desert Dust ◽  
Dust Aerosols ◽  
Near Ir ◽  
Biomass Burning Aerosol ◽  
Absorbing Aerosols ◽  
Aerosol Index

Abstract. Global Ozone Monitoring Experiment (GOME) Absorbing Aerosol Index (AAI) and AAI-related residue data were used to investigate areas with UV-absorbing aerosols. Time series of regionally averaged residues show the seasonal variation and trends of aerosols and clouds in climatologically important parts of the globe. GOME spectra were used to study scenes containing specific types of aerosols. AAI data are specifically sensitive to biomass burning aerosols (BBA) and desert dust aerosols (DDA). Areas where these aerosols are regularly found were analysed to find spectral fingerprints in the ultraviolet (UV), visible and near-infrared (near-IR), to establish an aerosol type classification of BBA and DDA. Spectral residues are different for BBA and DDA, but over deserts the surface albedo is dominant beyond the UV and spectral residues cannot be used over land. Over oceans, about half of the BBA scenes show a very high reflectance that is never observed for DDA scenes. However, in the case of low reflectance scenes BBA and DDA cannot be distinguished. This is in part due to the microphysical and optical properties of biomass burning aerosols, which are highly variable in time, making it difficult to specify them spectrally as one type. Because of their high hygroscopicity BBA are often found in the presence of clouds, which disturb the spectrum of the scenes. Desert dust aerosols are much less hygroscopic and behave spectrally more uniformly.

Crusading Companies in the 1365th Year of Our Lord

2020 ◽  
Vol 47 (1) ◽  
pp. 67-88
Author(s):  
Tamás Ölbei
Keyword(s):  
Roman Empire ◽  
Holy Roman Empire ◽  
Local Authorities ◽  
The Balkans ◽  
Different Sources

Louis of Hungary recognized the danger of the Ottomans and actively participated in the preparation of a crusade devoted to erasing the enemies of Christ from the Balkans. To achieve this he, along with Pope Urban v, the emperor Charles iv, and Charles v, designed a plan to send the most feared soldiers of their time, the “Magna Socieatas,” against the “Saracens,” the “proud disciples of Lucifer.” Under the leadership of the Arnauld de Cervole, “the Archpriest,” the routiers crossed the border of the Holy Roman Empire and intended to move towards the valley of the Danube to Hungary and later on to the Balkans. In my paper, I will analyze how the local authorities and people reacted to the migrating soldiers during their hundreds of kilometer long journey. I will describe what measures were taken by the towns and the magnates of the lands they traversed (Barrois, Lorraine, Alsace, Burgundy), what reactions we can read in the contemporary letters, and other different sources such as the chronicles and annals from Basel, Strasbourg, Lorraine, Metz. The sources used in my paper originate from the archives of Colmar, Kaysersberg, Selestat, and Strasbourg, as well as Dijon, Metz, and Barr-le-Duc.

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