Desert aerosol optical properties in Morocco

Tahiri, Abdelouahid; Diouri, Mohammed; Steli, Hanae; Marsli, Ibtissam; Meziane, Rajae; Ben-tayeb, Abdelmoula

doi:10.12988/es.2016.631

Cited by 10 publications

(7 citation statements)

References 7 publications

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“…They also found that urban and biomass burning aerosols were of local origin. The most recent published work on Morocco was reported by Tahiri et al [18,19]. They analyzed two AOD datasets measured at Saada (31.63°N; 8.16°W) and Ouarzazate (30.93°N; 6.91°W), two of the study sites of the present manuscript, over two successive years: 2012 and 2013.…”

Section: Introductionmentioning

confidence: 93%

“…Ouarzazate is a small town located east of the Atlas Mountains and north of the Sahara Desert, with almost no industrial activity. It has a pre-Saharan climate characterized by low rainfall with hot and dry summers [19]. The Saada and Ras-El-Aïn stations are located ∼15 km from the city of Marrakech and ∼60 km west of the Atlas Mountains.…”

Section: Site Descriptionmentioning

confidence: 99%

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Aerosol Distributions and Transport over Southern Morocco from Ground-Based and Satellite Observations (2004–2020)

et al. 2022

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The present study investigates the optical properties of aerosols on daily and seasonal scales with the use of the aerosol optical depth (AOD) and Angström exponent (AE) data retrieved from AErosol RObotic NETwork (AERONET) and collected at four stations in Southern Morocco—Saada (31.63° N; 8.16° W), Ouarzazate (30.93° N; 6.91° W), Oukaïmeden (31.21° N; 7.86° W) and Ras-El-Aïn (31.67° N; 7.60° W). An evaluation of the aerosol volumetric size distribution (AVSD) is also obtained for Saada and Ouarzazate. An AOD inter-comparison is performed between AERONET data and satellite sensors (MODerate resolution Imaging Spectroradiometer—MODIS), as well as assimilation products (Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) and Copernicus Atmosphere Monitoring Service (CAMS)), by the means of a linear regression. Regardless of site location and elevation, the results show the prevalence of the annual cycle of AOD, with a maximum in summer and a minimum in winter. In association with this seasonal variation, the variations in AE and AVSD showed an increase in coarse mode over Ouarzazate and Saada during summer (July to August), underlining that Southern Morocco is prone to the regular transport of desert dust on a seasonal basis. The inter-comparison reveals that the MERRA-2 dataset is slightly more appropriate for the study region, since it shows correlation coefficients (r) ranging from 0.758 to 0.844 and intercepts ranging from 0.021 to 0.070, depending on the study site. The statistical analysis of the back-trajectories simulated by the HYbrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model were consistent with the observations and confirmed the dominance of desert dust aerosols during the summer over the study region. On the other hand, the winter season reveals a predominance of anthropogenic and oceanic aerosols originating from the north and the west of the study site.

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Section: Introductionmentioning

confidence: 93%

Section: Site Descriptionmentioning

confidence: 99%

Aerosol Distributions and Transport over Southern Morocco from Ground-Based and Satellite Observations (2004–2020)

et al. 2022

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“…Tetouan, which is located in the north of Morocco on the Mediterranean coast, has a low concentration. Tinfou, a station located in the Sahara, has a high concentration due to its proximity to the source of natural dust emission (Knippertz et al, 355 2007;Tahiri et al, 2016). The urban concentration of Moroccan cities remains low compared to Delhi in India, for example, which has a concentration of about 232 µg/m 3 .…”

Section: Comparison With Other Stationsmentioning

confidence: 99%

First insights into Northern Africa high-altitude background aerosol chemical composition and source influences

Deabji

Fomba

Hajjaji

et al. 2021

Preprint

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Abstract. Field measurements were conducted to determine aerosol chemical composition in a newly established remote high-altitude site in North Africa to investigate the variations in aerosol composition useful in assessing global and regional changes in atmospheric composition. Particulate matter (PM10) filter samples (200) were collected at the Atlas Mohammed V atmospheric observatory (AM5) located in the Middle-Atlas Mountains in Morocco using a high-volume (HV) collector in a 12 h sampling interval from August to December 2017. The chemical composition of the samples was analyzed for trace metals, ions, elemental carbon, organic carbon, aliphatic hydrocarbons, and polycyclic aromatic hydrocarbon (PAHs) content. The results indicate that high-altitudes aerosol composition is influenced by both regional as well as trans-regional transport of emissions. However, local sources play an important role, especially during low wind speed periods, as observed for November and December. Despite the proximity of the site to the Sahara Desert, its influence on the atmospheric composition at this high-altitude site was mainly seasonal and accounted for only 14 % of the sampling duration. Background conditions at this remote site are characterized by low wind speeds (Av. 2.5 m/s) and mass concentrations in the range of 9.8 and 20 µg/m3. The chemical composition is found to be dominated by inorganic elements, mainly suspended dust (47 %) and ionic species (16 %), followed by organic matter (15 %), water content (12 %), and indeterminate mass (9 %). Biogenic organics contributed up to 7 % of the organic matter with high contributions from compounds such as Nonacosane, Heptacosane, and 2-Pentadecanone. The AM5 site is dominated by four main air mass inflow, which often leads to different aerosol chemical compositions. Mineral dust influenced was seasonal and ranged between 20 and 70 % of the PM mass with peaks observed during the summer and was accompanied by high concentrations of SO42− of up to 1.3 µg/m3. During winter, PM10 concentrations are low (

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“…In addition to their effects on cloud properties and precipitation [28], dust aerosols play important roles in biogeochemical cycles [29], atmospheric chemistry [30], visibility, and human health [31]. Various photometric measurement campaigns allowed to determine the desert dust volume size distribution with a radius between 0.05 and 15 µm [32,33], but for a limited period of time, no longer than 2 years of observation. According to Tahiri et al [33], from 2013 AERONET measurements, the volume size distributions at 3 Moroccan sites (Oujda, Saada, and Ouarzazate) showed the same shape with median radii around 0.15 µm for fine particles and 2.59 µm for coarse particles.…”

Section: Introductionmentioning

confidence: 99%

Aerosol Distributions and Sahara Dust Transport in Southern Morocco, from Ground-Based and Satellite Observations

et al. 2022

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The present study investigates aerosols distributions and a strong Sahara dust-storm event that occurred by early August 2018, in the South of Morocco. We used columnar aerosol optical depth (AOD), Angstrom Exponent (AE) and volume size distributions (VSD) as derived from ground-based observations by 2 AERONET (AErosol RObotic NETwork) sun-photometers at Saada (31.63°N, 8.16°W) and Ouarzazate (30.93°N, 6.91°W) sites, over the periods 2004–2019 and 2012–2015, respectively. The monthly seasonal distributions of AOD, AE, and VSD showed a seasonal trend dominated by the annual cycle, with a maximum aerosol load during summer (July–August) and a minimum in winter (December–January), characterized by a coarse mode near the radius of 2.59 μm and a fine mode at the radius of 0.16 μm, respectively. Indeed, this study showed that aerosol populations in southern Morocco are dominated by Saharan desert dust, especially during the summer season. The latter can sometimes be subject of dust-storm events. The case study presented in this paper reports on one of these events, which happened in early August 2018. The HYSPLIT (HYbrid Single Particle Lagrangian Integrated Trajectory) model was used to simulate air-mass back-trajectories during the event. In agreement with ground-based (AERONET sun-photometers) and satellite (CALIOP, MODIS and AIRS) observations, HYSPLIT back-trajectories showed that the dust air-mass at the 4-km layer, the average height of the dust plume, has crossed southern Morocco over the Saada site, with a westward direction towards the Atlantic Ocean, before it changed northward up to the Portuguese coasts.

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Desert aerosol optical properties in Morocco

Cited by 10 publications

References 7 publications

Aerosol Distributions and Transport over Southern Morocco from Ground-Based and Satellite Observations (2004–2020)

Aerosol Distributions and Transport over Southern Morocco from Ground-Based and Satellite Observations (2004–2020)

First insights into Northern Africa high-altitude background aerosol chemical composition and source influences

Aerosol Distributions and Sahara Dust Transport in Southern Morocco, from Ground-Based and Satellite Observations

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