Evidence of anthropization of aerosols in the Saharan and peri-Saharan regions: Implications for the atmospheric transfer of solar radiation

El‐Metwally, Mossad; Korany, Mohamed; Boraiy, Mohamed; Ebada, E.; Wahab, M. M. Abdel; Hungershoefer, K.; Alfaro, Stéphane C.

doi:10.1016/j.jastp.2020.105199

Cited by 5 publications

(2 citation statements)

References 65 publications

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“…In most North Africa and the Middle East regions, the change rate of τ T (−0.006 to 0.0020 τ T yr −1 ) is lower than other regions; however, τ T of Tamanrasset sites increased as 0.0108 τ T yr −1 ) because of τ D . It is supported by the results from El-Metwally et al, 2020 [66]. The authors conclude that Tamanrasset is the site most affected by dust from the downwind Saharan sources in the Saharan/Arabian region.…”

Section: Annual Trend Of Dust Coarse-and Fine-mode Pollution Aodmentioning

confidence: 54%

Long-Term Variation Study of Fine-Mode Particle Size and Regional Characteristics Using AERONET Data

et al. 2022

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To identify the long-term trend of particle size variation, we analyzed aerosol optical depth (AOD, τ) separated as dust (τD) and coarse-(τPC) and fine-pollution particles (τPF) depending on emission sources and size. Ångström exponent values are also identified separately as total and fine-mode particles (αT and αPF). We checked these trends in various ways; (1) first-order linear regression analysis of the annual average values, (2) percent variation using the slope of linear regression method, and (3) a reliability analysis using the Mann–Kendall (MK) test. We selected 17 AERONET sun/sky radiometer sites classified into six regions, i.e., Europe, North Africa, the Middle East, India, Southeast Asia, and Northeast Asia. Although there were regional differences, τ decreased in Europe and Asian regions and increased in the Middle East, India, and North Africa. Values of τPC and τPF, show that aerosol loading caused by non-dust aerosols decreased in Europe and Asia and increased in India. In particular, τPF considerably decreased in Europe and Northeast Asia (95% confidential levels in MK-test), and τPC decreased in Northeast Asia (Z-values for Seoul and Osaka are −2.955 and −2.306, respectively, statistically significant if |z| ≥ 1.96). The decrease in τPC seems to be because of the reduction of primary and anthropogenic emissions from regulation by air quality policies. The meaningful result in this paper is that the particle size became smaller, as seen by values of αT that decreased by −3.30 to −30.47% in Europe, North Africa, and the Middle East because αT provides information on the particle size. Particle size on average became smaller over India and Asian regions considered in our study due to the decrease in coarse particles. In particular, an increase of αPF in most areas shows the probability that the average particle size of fine-mode aerosols became smaller in recent years. We presumed the cause of the increase in αT is because relatively large-sized fine-mode particles were eliminated due to air quality policies.

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Section: Annual Trend Of Dust Coarse-and Fine-mode Pollution Aodmentioning

confidence: 54%

Long-Term Variation Study of Fine-Mode Particle Size and Regional Characteristics Using AERONET Data

et al. 2022

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“…The spectral dependence of this AOD can be quantified by the means of the Angstro ¨m exponent (AE), which provides useful information on the type of aerosol present in the atmospheric column (El-Metwally et al, 2008;Masmoudi et al, 2015). Indeed, low AEs are associated with coarse (supermicron) dust-like particles, whereas large AEs correspond to finer (submicron) aerosols of anthropic origin (El-Metwally et al, 2020).…”

Section: Aeronet Datamentioning

confidence: 99%

Retrieving PM10 Surface Concentration from AERONET Aerosol Optical Depth: The Cairo and Delhi Megacities Case Studies

Said¹,

Salah²,

Wahab

et al. 2023

J Indian Soc Remote Sens

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Large concentrations of air-suspended particulate matter (PM) in megacities represent an important health risk for their populations, but PM time series are often missing or too short to quantify the associated burden of diseases. In this study, we propose a model for retrieving the surface PM in Cairo (Egypt) and Delhi (India) from the automated measurements of aerosol optical depth (AOD), precipitable water (PW), and Angström exponent (AE) performed by the sunphotometers of the Aerosol Robotics Network (AERONET). For this we exploit the (1) synchronous measurements performed from 2010 to 2015 at the headquarters of the Egyptian Meteorological Authority and in 2009 at the Gual Pahari station (25 km south of Delhi) and (2) the ERA5 estimate of the planetary boundary layer height (H). The correlation between the surface PM10 and the AOD is primarily controlled by the variations of PW and secondarily by those of H: for similar surface PM10 concentrations, the AOD tends to be the largest in summer because of the hygroscopic enhancement of the mass extinction efficiency (σ) of the particles and their dilution in the more developed mixing layer. The variations of composition also play a significant role in Cairo. This effect, particularly marked in spring (coinciding with the dust season), can be parameterized as a linear function of AE. Finally, we show that the variations of the surface PM10 concentration at the two sites can be retrieved simply from those of the AOD, PW, AE and H. At the weekly temporal resolution, the agreement between the model and the observations is very good at the two locations (correlation coefficient > 0.81, relative mean absolute error < 15%). This validates indirectly the assumption made in the development of the model, namely that the aerosols are mostly confined to the mixing layer of the two megacities and not transported in the free atmosphere. Provided a few years of surface PM measurements are available, the methodology proposed in this study could be easily applied to any other AERONET station.

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Elemental ratios as tracers of the sources of mineral dust in north-eastern Sahara

Boraiy,

El-Metwally,

Borbon

et al. 2023

Int. J. Environ. Sci. Technol.

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The objective of this study is to confirm the possibility of tracing sources of airborne mineral dust using elemental ratios. The region of study is the north-eastern part of the Sahara where dust compositional data were lacking; 272 mineral dust samples collected at 3 experimental stations of Egypt were analyzed by X-ray fluorescence. Based on the mineral dust concentration, 65% of the samples correspond to moderate (3–10 μg m−3), 22% to medium (10–25 μg m−3), and 13% to intense (> 25 μg m−3) dust events. The Ca/Al and (Mg + Ca)/Fe ratios were found to be strongly correlated and their ranges of variation to cover are more than one order of magnitude, which confirms their interest for the tracing of the dust sources. Using a combination of MODIS satellite observations, HYSPLIT back-trajectory analysis, and simulations with dust emission models, the large (> 6) and intermediate (2–6) Ca/Al ratios were shown to correspond to dust originating from saline playas (chotts) and calcareous surfaces, respectively. Conversely, the lowest (< 2) ratios correspond to dust emitted by siliceous sand seas (ergs). Therefore, a classification of the dust in 3 categories (erg-like, calcareous, and chott-like) based on Ca/Al is proposed. The events of moderate to medium intensity are dominated by chott-like and calcareous dust, which suggests that these sources are activated during erosion events of limited (local) extension. Conversely, the fact that the dust composition is more likely to be of the erg-like type during intense events underlines the dominant role played by sand dune fields during major erosion events.

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Evidence of anthropization of aerosols in the Saharan and peri-Saharan regions: Implications for the atmospheric transfer of solar radiation

Cited by 5 publications

References 65 publications

Long-Term Variation Study of Fine-Mode Particle Size and Regional Characteristics Using AERONET Data

Long-Term Variation Study of Fine-Mode Particle Size and Regional Characteristics Using AERONET Data

Retrieving PM10 Surface Concentration from AERONET Aerosol Optical Depth: The Cairo and Delhi Megacities Case Studies

Elemental ratios as tracers of the sources of mineral dust in north-eastern Sahara

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