scholarly journals Size distribution and optical properties of mineral dust aerosols transported in the western Mediterranean

2015 ◽  
Vol 15 (15) ◽  
pp. 21607-21669 ◽  
Author(s):  
C. Denjean ◽  
F. Cassola ◽  
A. Mazzino ◽  
S. Triquet ◽  
S. Chevaillier ◽  
...  
Keyword(s):  
Optical Properties ◽  
Mediterranean Basin ◽  
Mineral Dust ◽  
Regional Climate ◽  
Source Region ◽  
Western Mediterranean ◽  
Source Regions ◽  
Western Mediterranean Basin ◽  
Large Particles ◽  
The Mediterranean

Abstract. This study presents in situ aircraft measurements of Saharan mineral dust transported over the western Mediterranean basin in June–July 2013 during the ChArMEx/ADRIMED (the Chemistry-Aerosol Mediterranean Experiment/Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region) airborne campaign. Dust events differing in terms of source region (Algeria, Tunisia and Morocco), time of tranport (1–5 days) and height of transport were sampled. Mineral dust were transported above the marine boundary layer, which conversely was dominated by pollution and marine aerosols. The dust vertical structure was extremely variable and characterized by either a single layer or a more complex and stratified structure with layers originating from different source regions. Mixing of mineral dust with pollution particles was observed depending on the height of transport of the dust layers. Dust layers carried higher concentration of pollution particles at intermediate altitude (1–3 km) than at elevated altitude (> 3 km), resulting in scattering Angstrom exponent up to 2.2 within the intermediate altitude. However, the optical properties of the dust plumes remained practically unchanged with respect to values previously measured over source regions, regardless of the altitude. Moderate light absorption of the dust plumes was observed with values of aerosol single scattering albedo at 530 nm ranging from 0.90 to 1.00 ± 0.04. Concurrent calculations from the aerosol chemical composition revealed a negligible contribution of pollution particles to the absorption properties of the dust plumes that was due to a low contribution of refractory black carbon in regards to the fraction of dust and sulfate particles. This suggests that, even in the presence of moderate pollution, likely a persistent feature in the Mediterranean, the optical properties of the dust plumes could be assimilated to those of native dust in radiative transfer simulations, modeling studies and satellite retrievals over the Mediterranean. Measurements also showed that the coarse mode of mineral dust was conserved even after 5 days of transport in the Mediterranean, which contrasts with the gravitational depletion of large particles observed during the transport of dust plumes over the Atlantic. Simulations with the WRF mesoscale meteorological model highlighted a strong vertical turbulence within the dust layers that could prevent deposition of large particles during their atmospheric transport. This has important implications for the dust radiative effects due to surface dimming, atmospheric heating and cloud formation. The results presented here add to the observational dataset necessary for evaluating the role of mineral dust on the regional climate and rainfall patterns in the western Mediterranean basin.

scholarly journals Size distribution and optical properties of mineral dust aerosols transported in the western Mediterranean

2016 ◽  
Vol 16 (2) ◽  
pp. 1081-1104 ◽  
Author(s):  
C. Denjean ◽  
F. Cassola ◽  
A. Mazzino ◽  
S. Triquet ◽  
S. Chevaillier ◽  
...  
Keyword(s):  
Optical Properties ◽  
Mediterranean Basin ◽  
Mineral Dust ◽  
Atmospheric Transport ◽  
Regional Climate ◽  
Western Mediterranean ◽  
Source Regions ◽  
Western Mediterranean Basin ◽  
Large Particles ◽  
The Mediterranean

Abstract. This study presents in situ aircraft measurements of Saharan mineral dust transported over the western Mediterranean basin in June–July 2013 during the ChArMEx/ADRIMED (the Chemistry-Aerosol Mediterranean Experiment/Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region) airborne campaign. Dust events differing in terms of source region (Algeria, Tunisia and Morocco), time of transport (1–5 days) and height of transport were sampled. Mineral dust were transported above the marine boundary layer, which conversely was dominated by pollution and marine aerosols. The dust vertical structure was extremely variable and characterized by either a single layer or a more complex and stratified structure with layers originating from different source regions. Mixing of mineral dust with pollution particles was observed depending on the height of transport of the dust layers. Dust layers carried a higher concentration of pollution particles below 3 km above sea level (a.s.l.) than above 3 km a.s.l., resulting in a scattering Ångström exponent up to 2.2 below 3 km a.s.l. However, the optical properties of the dust plumes remained practically unchanged with respect to values previously measured over source regions, regardless of the altitude. Moderate absorption of light by the dust plumes was observed with values of aerosol single scattering albedo at 530 nm ranging from 0.90 to 1.00. Concurrent calculations from the aerosol chemical composition revealed a negligible contribution of pollution particles to the absorption properties of the dust plumes that was due to a low contribution of refractory black carbon in regards to the fraction of dust and sulfate particles. This suggests that, even in the presence of moderate pollution, likely a persistent feature in the Mediterranean, the optical properties of the dust plumes could be assumed similar to those of native dust in radiative transfer simulations, modelling studies and satellite retrievals over the Mediterranean. Measurements also showed that the coarse mode of mineral dust was conserved even after 5 days of transport in the Mediterranean, which contrasts with the gravitational depletion of large particles observed during the transport of dust plumes over the Atlantic. Simulations with the WRF mesoscale meteorological model highlighted a strong vertical turbulence within the dust layers that could prevent deposition of large particles during their atmospheric transport. This has important implications for the dust radiative effects due to surface dimming, atmospheric heating and cloud formation. The results presented here add to the observational data set necessary for evaluating the role of mineral dust on the regional climate and rainfall patterns in the western Mediterranean basin and understanding their atmospheric transport at global scale.

scholarly journals Simulation of fine organic aerosols in the western Mediterranean area during the ChArMEx 2013 summer campaign

2018 ◽  
Vol 18 (10) ◽  
pp. 7287-7312 ◽  
Author(s):  
Arineh Cholakian ◽  
Matthias Beekmann ◽  
Augustin Colette ◽  
Isabelle Coll ◽  
Guillaume Siour ◽  
...  
Keyword(s):  
Mediterranean Basin ◽  
Mass Concentration ◽  
Organic Aerosols ◽  
Western Mediterranean ◽  
Basis Set ◽  
Aerosol Formation ◽  
Standard Scheme ◽  
Western Mediterranean Basin ◽  
The Mediterranean ◽  
Fine Organic

Abstract. The simulation of fine organic aerosols with CTMs (chemistry–transport models) in the western Mediterranean basin has not been studied until recently. The ChArMEx (the Chemistry-Aerosol Mediterranean Experiment) SOP 1b (Special Observation Period 1b) intensive field campaign in summer of 2013 gathered a large and comprehensive data set of observations, allowing the study of different aspects of the Mediterranean atmosphere including the formation of organic aerosols (OAs) in 3-D models. In this study, we used the CHIMERE CTM to perform simulations for the duration of the SAFMED (Secondary Aerosol Formation in the MEDiterranean) period (July to August 2013) of this campaign. In particular, we evaluated four schemes for the simulation of OA, including the CHIMERE standard scheme, the VBS (volatility basis set) standard scheme with two parameterizations including aging of biogenic secondary OA, and a modified version of the VBS scheme which includes fragmentation and formation of nonvolatile OA. The results from these four schemes are compared to observations at two stations in the western Mediterranean basin, located on Ersa, Cap Corse (Corsica, France), and at Cap Es Pinar (Mallorca, Spain). These observations include OA mass concentration, PMF (positive matrix factorization) results of different OA fractions, and 14C observations showing the fossil or nonfossil origins of carbonaceous particles. Because of the complex orography of the Ersa site, an original method for calculating an orographic representativeness error (ORE) has been developed. It is concluded that the modified VBS scheme is close to observations in all three aspects mentioned above; the standard VBS scheme without BSOA (biogenic secondary organic aerosol) aging also has a satisfactory performance in simulating the mass concentration of OA, but not for the source origin analysis comparisons. In addition, the OA sources over the western Mediterranean basin are explored. OA shows a major biogenic origin, especially at several hundred meters height from the surface; however over the Gulf of Genoa near the surface, the anthropogenic origin is of similar importance. A general assessment of other species was performed to evaluate the robustness of the simulations for this particular domain before evaluating OA simulation schemes. It is also shown that the Cap Corse site presents important orographic complexity, which makes comparison between model simulations and observations difficult. A method was designed to estimate an orographic representativeness error for species measured at Ersa and yields an uncertainty of between 50 and 85 % for primary pollutants, and around 2–10 % for secondary species.

scholarly journals Variability of mineral dust deposition in the western Mediterranean basin and south-east of France

2016 ◽  
Vol 16 (14) ◽  
pp. 8749-8766 ◽  
Author(s):  
Julie Vincent ◽  
Benoit Laurent ◽  
Rémi Losno ◽  
Elisabeth Bon Nguyen ◽  
Pierre Roullet ◽  
...  
Keyword(s):  
Mediterranean Basin ◽  
Mineral Dust ◽  
Sampling Site ◽  
Regional Scale ◽  
Western Mediterranean ◽  
Saharan Dust ◽  
Deposition Flux ◽  
Dust Deposition ◽  
Western Mediterranean Basin ◽  
Provenance Areas

Abstract. Previous studies have provided some insight into the Saharan dust deposition at a few specific locations from observations over long time periods or intensive field campaigns. However, no assessment of the dust deposition temporal variability in connection with its regional spatial distribution has been achieved so far from network observations over more than 1 year. To investigate dust deposition dynamics at the regional scale, five automatic deposition collectors named CARAGA (Collecteur Automatique de Retombées Atmosphériques insolubles à Grande Autonomie in French) have been deployed in the western Mediterranean region during 1 to 3 years depending on the station. The sites include, from south to north, Lampedusa, Majorca, Corsica, Frioul and Le Casset (southern French Alps). Deposition measurements are performed on a common weekly period at the five sites. The mean dust deposition fluxes are higher close to the northern African coasts and decrease following a south–north gradient, with values from 7.4 g m−2 year−1 in Lampedusa (35°31′ N, 12°37′ E) to 1 g m−2 year−1 in Le Casset (44°59′ N, 6°28′ E). The maximum deposition flux recorded is of 3.2 g m−2 wk−1 in Majorca with only two other events showing more than 1 g m−2 wk−1 in Lampedusa, and a maximum of 0.5 g m−2 wk−1 in Corsica. The maximum value of 2.1 g m−2 year−1 observed in Corsica in 2013 is much lower than existing records in the area over the 3 previous decades (11–14 g m−2 year−1). From the 537 available samples, 98 major Saharan dust deposition events have been identified in the records between 2011 and 2013. Complementary observations provided by both satellite and air mass trajectories are used to identify the dust provenance areas and the transport pathways from the Sahara to the stations for the studied period. Despite the large size of African dust plumes detected by satellites, more than 80 % of the major dust deposition events are recorded at only one station, suggesting that the dust provenance, transport and deposition processes (i.e. wet vs. dry) of dust are different and specific for the different deposition sites in the Mediterranean studied area. The results tend to indicate that wet deposition is the main form of deposition for mineral dust in the western Mediterranean basin, but the contribution of dry deposition (in the sense that no precipitation was detected at the surface) is far from being negligible, and contributes 10 to 46 % to the major dust deposition events, depending on the sampling site.

scholarly journals Aircraft vertical profiles during summertime regional and Saharan dust scenarios over the north-western Mediterranean Basin: aerosol optical and physical properties

2020 ◽  
Author(s):  
Jesús Yus-Díez ◽  
Marina Ealo ◽  
Marco Pandolfi ◽  
Noemí Perez ◽  
Gloria Titos ◽  
...  
Keyword(s):  
Optical Properties ◽  
Vertical Distribution ◽  
Asymmetry Parameter ◽  
Mediterranean Basin ◽  
Western Mediterranean ◽  
Saharan Dust ◽  
Vertical Profiles ◽  
Measurement Campaign ◽  
Western Mediterranean Basin ◽  
Ne Spain

Abstract. Accurate measurements of the horizontal and vertical distribution of atmospheric aerosol particle optical properties are key for a better understanding of their impact on the climate. Here we present the results of a measurement campaign based on instrumented flights over NE Spain. We measured vertical profiles of size segregated atmospheric particulate matter (PM) mass concentrations and multi-wavelength scattering and absorption coefficients in the Western Mediterranean Basin (WMB). The campaign took place during typical summer conditions, characterized by the development of a vertical multi-layer structure, under both summer regional pollution episodes (REG) and Saharan dust events (SDE). REG patterns in the region form under high insolation and scarce precipitation in summer, favoring layering of highly-aged fine PM strata in the lower few km a.s.l. The REG scenario prevailed during the entire measurement campaign. Additionally, African dust outbreaks and plumes from North African wildfires influenced the study area. The vertical profiles of climate relevant intensive optical parameters such as single scattering albedo (SSA), asymmetry parameter (g), scattering, absorption and SSA Angstrom exponents (SAE, AAE, SSAAE), and PM mas scattering and absorption cross sections (MSC and MAE) were derived from the measurements. Moreover, we compared the aircraft measurements with those performed at two GAW/ACTRIS surface measurement stations located in NE Spain, namely: Montseny (MSY; regional background) and Montsec d'Ares (MSA; remote site). Airborne in-situ measurements and ceilometer ground-based remote measurements identified aerosol air masses at altitude up to more than 3.5 km a.s.l. The vertical profiles of the optical properties markedly changed according to the prevailing atmospheric scenarios. During SDE the SAE was low along the profiles, reaching values  2.0 and the asymmetry parameter g was rather low (0.5–0.6) due to the prevalence of fine PM which were characterized by an AAE close to 1.0 suggesting a fossil fuel combustion origin. During REG, some of the layers featured larger AAE (> 1.5), relatively low SSA at 525 nm ( 9 m2 g−1) and were associated to the influence of PM from wildfires. Overall, the SSA and MSC near the ground ranged around 0.85 and 3 m2 g−1, respectively and increased at higher altitudes, reaching values above 0.95 and up to 9 m2 g−1. The PM, MSC and MAE were on average larger during REG compared to SDE due to the larger scattering and absorption efficiency of fine PM compared with dust. The SSA and MSC had quite similar vertical profiles and often both increased with height indicating the progressive shift toward PM with larger scattering efficiency with altitude. This study contributes to our understanding of regional aerosol vertical distribution and optical properties in the WMB and the results will be useful for improving future climate projections and remote sensing/satellite retrieval algorithms.

scholarly journals Evidence of a prolonged drought ca. 4200 yr BP correlated with prehistoric settlement abandonment from the Gueldaman GLD1 Cave, Northern Algeria

2016 ◽  
Vol 12 (1) ◽  
pp. 1-14 ◽  
Author(s):  
J. Ruan ◽  
F. Kherbouche ◽  
D. Genty ◽  
D. Blamart ◽  
H. Cheng ◽  
...  
Keyword(s):  
Mediterranean Basin ◽  
Eastern Mediterranean ◽  
Western Mediterranean ◽  
Faunal Remains ◽  
Carbon And Oxygen Isotopes ◽  
Northern Algeria ◽  
Western Mediterranean Basin ◽  
Prolonged Drought ◽  
Eastern Mediterranean Basin ◽  
The Mediterranean

Abstract. Middle Holocene cultures have been widely studied around the Eastern-Mediterranean basin in the last 30 years and past cultural activities have been commonly linked with regional climate changes. However, in many cases such linkage is equivocal, in part due to existing climatic evidence that has been derived from areas outside the distribution of ancient settlements, leading to uncertainty from complex spatial heterogeneity in both climate and demography. A few high-resolution well-dated paleoclimate records were recently established using speleothems in the Central and Eastern-Mediterranean basin, however, the scarcity of such records in the western part of the Mediterranean prevents us from correlating past climate evolutions across the basin and deciphering climate–culture relation at fine timescales. Here we report the first decadal-resolved Mid-Holocene climate proxy records from the Western-Mediterranean basin based on the stable carbon and oxygen isotopes analyses of two U/Th dated stalagmites from the Gueldaman GLD1 Cave in Northern Algeria. Comparison of our records with those from Italy and Israel reveals synchronous (multi) centennial dry phases centered at ca. 5600, ca. 5200 and ca. 4200 yr BP across the Mediterranean basin. New calibrated radiocarbon dating constrains reasonably well the age of rich anthropogenic deposits (e.g., faunal remains, pottery, charcoal) excavated inside the cave, which allows the comparison between in situ evidence of human occupation and of climate change. This approach shows that the timing of a prolonged drought at ca. 4400–3800 yr BP blankets the onset of cave abandonment shortly after ca. 4403 cal yr BP, supporting the hypothesis that a climate anomaly may have played a role in this cultural disruption.

scholarly journals Fuel loading and flammability in the Mediterranean Basin woody species with different post-fire regenerative strategies

2010 ◽  
Vol 19 (6) ◽  
pp. 783 ◽  
Author(s):  
S. Saura-Mas ◽  
S. Paula ◽  
J. G. Pausas ◽  
F. Lloret
Keyword(s):  
Mediterranean Basin ◽  
Fire Risk ◽  
Woody Species ◽  
Western Mediterranean ◽  
Fuel Load ◽  
Fuel Loading ◽  
Selective Pressures ◽  
Western Mediterranean Basin ◽  
The Mediterranean ◽  
The Mediterranean Basin

The flammability and combustibility of plant communities are determined by species features related to growth-form, structure and physiology. In some ecosystems, such as the Mediterranean ones, these characteristics may contribute to the existence of fire-prone species. We measured several parameters associated with the flammability and fuel loading of dominant woody species with different post-fire regenerative strategies (seeders and non-seeders) in shrublands in the western Mediterranean Basin. Overall, seeder species show lower fuel load but are more prone to burning owing to a higher dead-to-live fuel ratio, live fine-fuel proportion and dead fine-fuel proportion. Moreover, they burst into flame at lower temperatures than non-seeders. In the Mediterranean Basin, most seeder species emerged mainly during the Quaternary, under a highly fluctuating Mediterranean climate and during recurrent fires. We propose that properties related to the combustibility and flammability of seeders may be the result of selective pressures associated with both fire and climate. These results suggest that ecosystems dominated by seeder species are more susceptible to fire risk than those dominated by non-seeder species in the Mediterranean Basin. Therefore, the proportion of these types of species resulting from previous fire or management history is likely to determine the characteristics of future fire events.

scholarly journals Aircraft vertical profiles during summertime regional and Saharan dust scenarios over the north-western Mediterranean basin: aerosol optical and physical properties

2021 ◽  
Vol 21 (1) ◽  
pp. 431-455
Author(s):  
Jesús Yus-Díez ◽  
Marina Ealo ◽  
Marco Pandolfi ◽  
Noemí Perez ◽  
Gloria Titos ◽  
...  
Keyword(s):  
Optical Properties ◽  
Vertical Distribution ◽  
Asymmetry Parameter ◽  
Mediterranean Basin ◽  
Western Mediterranean ◽  
Saharan Dust ◽  
Vertical Profiles ◽  
Measurement Campaign ◽  
Western Mediterranean Basin ◽  
North Eastern

Abstract. Accurate measurements of the horizontal and vertical distribution of atmospheric aerosol particle optical properties are key for a better understanding of their impact on the climate. Here we present the results of a measurement campaign based on instrumented flights over north-eastern Spain. We measured vertical profiles of size-segregated atmospheric particulate matter (PM) mass concentrations and multi-wavelength scattering and absorption coefficients in the western Mediterranean basin (WMB). The campaign took place during typical summer conditions, characterized by the development of a vertical multi-layer structure, under both summer regional pollution episodes (REGs) and Saharan dust events (SDEs). REG patterns in the region form under high insolation and scarce precipitation in summer, favouring layering of highly aged fine-PM strata in the lower few kma.s.l. The REG scenario prevailed during the entire measurement campaign. Additionally, African dust outbreaks and plumes from northern African wildfires influenced the study area. The vertical profiles of climate-relevant intensive optical parameters such as single-scattering albedo (SSA); the asymmetry parameter (g); scattering, absorption and SSA Ångström exponents (SAE, AAE and SSAAE); and PM mass scattering and absorption cross sections (MSC and MAC) were derived from the measurements. Moreover, we compared the aircraft measurements with those performed at two GAW–ACTRIS (Global Atmosphere Watch–Aerosol, Clouds and Trace Gases) surface measurement stations located in north-eastern Spain, namely Montseny (MSY; regional background) and Montsec d'Ares (MSA; remote site). Airborne in situ measurements and ceilometer ground-based remote measurements identified aerosol air masses at altitudes up to more than 3.5 kma.s.l. The vertical profiles of the optical properties markedly changed according to the prevailing atmospheric scenarios. During SDE the SAE was low along the profiles, reaching values < 1.0 in the dust layers. Correspondingly, SSAAE was negative, and AAE reached values up to 2.0–2.5, as a consequence of the UV absorption increased by the presence of the coarse dust particles. During REG, the SAE increased to > 2.0, and the asymmetry parameter g was rather low (0.5–0.6) due to the prevalence of fine PM, which was characterized by an AAE close to 1.0, suggesting a fossil fuel combustion origin. During REG, some of the layers featured larger AAE (> 1.5), relatively low SSA at 525 nm (< 0.85) and high MSC (> 9 m2 g−1) and were associated with the influence of PM from wildfires. Overall, the SSA and MSC near the ground ranged around 0.85 and 3 m2 g−1, respectively, and increased at higher altitudes, reaching values above 0.95 and up to 9 m2 g−1. The PM, MSC and MAC were on average larger during REG compared to SDE due to the larger scattering and absorption efficiency of fine PM compared with dust. The SSA and MSC had quite similar vertical profiles and often both increased with height indicating the progressive shift toward PM with a larger scattering efficiency with altitude. This study contributes to our understanding of regional-aerosol vertical distribution and optical properties in the WMB, and the results will be useful for improving future climate projections and remote sensing or satellite retrieval algorithms.

scholarly journals New records of amphipod crustaceans along the Israeli Mediterranean coast, including a rare Mediterranean endemic species, Maera schieckei Karaman & Ruffo, 1971

2020 ◽  
Vol 8 ◽  
Author(s):  
Sabrina Lo Brutto ◽  
Davide Iaciofano
Keyword(s):  
Mediterranean Sea ◽  
Mediterranean Basin ◽  
Eastern Mediterranean ◽  
Aegean Sea ◽  
Western Mediterranean ◽  
Mediterranean Coast ◽  
Tyrrhenian Sea ◽  
Western Mediterranean Basin ◽  
The Mediterranean ◽  
Distribution And Ecology

A survey has been carried out at four Israeli rocky sites to evaluate the diversity of the amphipod fauna on various hard substrates, still scarcely monitored, as potential pabulum for amphipod crustacean species. A survey of shallow rocky reefs along the Mediterranean coast of Israel recovered 28 species and integrated the Amphipoda checklist for the country ofIsrael with 12 newly-recorded species. Such renewed national list includes Maera schieckei Karaman &amp; Ruffo, 1971, a rare species endemic to the Mediterranean Sea, recorded here for the first time from the southern Levant Basin. The species, described from specimens collected in the Tyrrhenian Sea in 1970, has been only recorded eight times within the whole Mediterranean Sea. A revision of the bibliography on the distribution and ecology of M. schieckei showed that, although mentioned only for the western Mediterranean basin by some authors, it is listed in the checklist of amphipods of the Aegean Sea and neighbouring seas and has been found in the eastern Mediterranean basin since 1978. Maera schieckei was rarely found in the Mediterranean, one of the most studied marine biogeographic region as concerns the amphipod fauna; and the species seems to prefer bays or gulf areas. The role of updating and monitoring faunal composition should be re-evaluated.

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