scholarly journals Saharan dust aerosol over the central Mediterranean Sea: PM<sub>10</sub> chemical composition and concentration versus optical columnar measurements

2014 ◽  
Vol 14 (4) ◽  
pp. 2039-2054 ◽  
Author(s):  
M. Marconi ◽  
D. M. Sferlazzo ◽  
S. Becagli ◽  
C. Bommarito ◽  
G. Calzolai ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Mediterranean Sea ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Saharan Dust ◽  
Central Mediterranean ◽  
Source Areas ◽  
Central Mediterranean Sea ◽  
Dust Events ◽  
The Eu

Abstract. This study aims to determine the mineral contribution to PM10 in the central Mediterranean Sea, based on 7 yr of daily PM10 samplings made on the island of Lampedusa (35.5° N, 12.6° E). The chemical composition of the PM10 samples was determined by ion chromatography for the main ions, and, on selected samples, by particle-induced X-ray emission (PIXE) for the total content of crustal markers. Aerosol optical depth measurements were carried out in parallel to the PM10 sampling. The average PM10 concentration at Lampedusa over the period June 2004–December 2010 is 31.5 μg m−3, with low interannual variability. The annual means are below the EU annual standard for PM10, but 9.9% of the total number of daily data exceeds the daily threshold value established by the European Commission for PM (50 μg m−3, European Community, EC/30/1999). The Saharan dust contribution to PM10 was derived by calculating the contribution of Al, Si, Fe, Ti, non-sea-salt (nss) Ca, nssNa, and nssK oxides in samples in which PIXE data were available. Cases in which crustal content exceeded the 75th percentile of the crustal oxide content distribution were identified as elevated dust events. Using this threshold, we obtained 175 events. Fifty-five elevated dust events (31.6%) displayed PM10 higher than 50 μg m−3, with dust contributing by 33% on average. The crustal contribution to PM10 has an annual average value of 5.42 μg m−3, and reaches a value as high as 67.9 μg m−3 (corresponding to 49% of PM10) during an intense Saharan dust event. The crustal content estimated from a single tracer, such as Al or Ca, is in good agreement with the one calculated as the sum of the metal oxides. Conversely, larger crustal contents are derived by applying the EU guidelines for demonstration and subtraction of exceedances in PM10 levels due to high background of natural aerosol. The crustal aerosol amount and contribution to PM10 showed a very small seasonal dependence; conversely, the dust columnar burden displays an evident annual cycle, with a strong summer maximum (monthly average aerosol optical depth at 500 nm up to 0.28 in June–August). We found that 71.3% of the dust events identified from optical properties over the atmospheric column display a high dust content at the ground level. Conversely, the remaining 28.7% of cases present a negligible or small impact on the surface aerosol composition due to the transport processes over the Mediterranean Sea, where dust frequently travels above the marine boundary layer, especially in summer. Based on backward trajectories, two regions, one in Algeria–Tunisia, and one in Libya, are identified as main source areas for intense dust episodes occurring mainly in autumn and winter. Data on the bulk composition of mineral aerosol arising from these two source areas are scarce; results on characteristic ratios between elements show somewhat higher values of Ca / Al and (Ca + Mg) / Fe (2.5 ± 1.0, and 4.7 ± 2.0, respectively) for Algeria–Tunisia than for Libyan origin (Ca / Al = 1.9 ± 0.7 and (Ca + Mg) / Fe = 3.3 ± 1.1).

scholarly journals Atmospheric deposition of organic matter at a remote site in the central Mediterranean Sea: implications for the marine ecosystem

2020 ◽  
Vol 17 (13) ◽  
pp. 3669-3684 ◽  
Author(s):  
Yuri Galletti ◽  
Silvia Becagli ◽  
Alcide di Sarra ◽  
Margherita Gonnelli ◽  
Elvira Pulido-Villena ◽  
...  
Keyword(s):  
Time Series ◽  
Organic Matter ◽  
Atmospheric Deposition ◽  
Mediterranean Sea ◽  
High Variability ◽  
Saharan Dust ◽  
Organic Substances ◽  
Remote Site ◽  
Central Mediterranean ◽  
Central Mediterranean Sea

Abstract. Atmospheric fluxes of dissolved organic matter (DOM) were studied for the first time on the island of Lampedusa, a remote site in the central Mediterranean Sea (Med Sea), between 19 March 2015 and 1 April 2017. The main goals of this study were to quantify total atmospheric deposition of DOM in this area and to evaluate the impact of Saharan dust deposition on DOM dynamics in the surface waters of the Mediterranean Sea. Our data show high variability in DOM deposition rates without a clear seasonality and a dissolved organic carbon (DOC) input from the atmosphere of 120.7 mmol DOC m−2 yr−1. Over the entire time series, the average dissolved organic phosphorus (DOP) and dissolved organic nitrogen (DON) contributions to the total dissolved pools were 40 % and 26 %, respectively. The data on atmospheric elemental ratios also show that each deposition event is characterized by a specific elemental ratio, suggesting a high variability in DOM composition and the presence of multiple sources. This study indicates that the organic substances transported by Saharan dust on Lampedusa mainly come from a natural sea spray and that Saharan dust can be an important carrier of organic substances even though the load of DOC associated with dust is highly variable. Our estimates suggest that atmospheric input has a larger impact on the Med Sea than on the global ocean. Further, DOC fluxes from the atmosphere to the Med Sea can be up to 6 times larger than total river input. Longer time series combined with modeling would greatly improve our understanding of the response of DOM dynamics in the Med Sea to the change in aerosol deposition pattern due to the effect of climate change.

scholarly journals Atmospheric deposition of organic matter at a remote site in the Central Mediterranean Sea: implications for marine ecosystem

2020 ◽  
Author(s):  
Yuri Galletti ◽  
Silvia Becagli ◽  
Alcide di Sarra ◽  
Margherita Gonnelli ◽  
Elvira Pulido-Villena ◽  
...  
Keyword(s):  
Time Series ◽  
Organic Matter ◽  
Atmospheric Deposition ◽  
Mediterranean Sea ◽  
High Variability ◽  
Saharan Dust ◽  
Organic Substances ◽  
Remote Site ◽  
Central Mediterranean ◽  
Central Mediterranean Sea

Abstract. Atmospheric fluxes of dissolved organic matter (DOM) were studied for the first time at the Island of Lampedusa, a remote site in the Central Mediterranean Sea (Med Sea), close to the Sahara desert, between 19 March 2015 and 1 April 2017. The main goals of this work are: to quantify total atmospheric deposition of DOM in this area and to evaluate the impact of dust deposition on DOM dynamics in the surface waters of the Mediterranean Sea. Our data show high variability in DOM deposition rates without a clear seasonality and allow to estimate a dissolved organic carbon (DOC) input from the atmosphere of 120.7 mmol DOC m−2 yr−1. Over the entire time-series, the average dissolved organic phosphorous (DOP) and dissolved organic nitrogen (DON) contributions to the total dissolved pools were 40 % and 26 %, respectively. The data on atmospheric elemental ratios also show that each deposition event is characterized by a specific elemental ratio, suggesting a high variability in DOM composition and the presence of multiple sources. This study indicates that the organic substances transported by Saharan dust at Lampedusa site mainly have natural origin, especially from sea spray and that Saharan dust can be an important carrier of organic substances, even if the load of DOC associated with dust is highly variable. Our estimates suggest that atmospheric input has an impact to the Med Sea larger than to the global ocean and that DOC fluxes from the atmosphere to the Med Sea can be up to 6-fold larger than river input. Longer time series, combined with a modelling effort, are therefore mandatory in order to investigate the response of DOM dynamics in the Med Sea to the change in aerosol deposition pattern due to the effect of climate change.

scholarly journals Sun photometer retrievals of Saharan dust properties over Barbados during SALTRACE

2019 ◽  
Vol 19 (23) ◽  
pp. 14571-14583 ◽  
Author(s):  
Carlos Toledano ◽  
Benjamín Torres ◽  
Cristian Velasco-Merino ◽  
Dietrich Althausen ◽  
Silke Groß ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Saharan Dust ◽  
Caribbean Region ◽  
The Sun ◽  
Concentration Data ◽  
The Caribbean ◽  
Sun Photometer ◽  
Dust Events

Abstract. The Saharan Aerosol Long-Range Transport and Aerosol–Cloud-Interaction Experiment (SALTRACE) was devoted to the investigation of Saharan dust properties over the Caribbean. The campaign took place in June–July 2013. A wide set of ground-based and airborne aerosol instrumentation was deployed at the island of Barbados for a comprehensive experiment. Several sun photometers performed measurements during this campaign: two AERONET (Aerosol Robotic Network) Cimel sun photometers and the Sun and Sky Automatic Radiometer (SSARA). The sun photometers were co-located with the ground-based multi-wavelength lidars BERTHA (Backscatter Extinction lidar Ratio Temperature Humidity profiling Apparatus) and POLIS (Portable Lidar System). Aerosol properties derived from direct sun and sky radiance observations are analyzed, and a comparison with the co-located lidar and in situ data is provided. The time series of aerosol optical depth (AOD) allows identifying successive dust events with short periods in between in which the marine background conditions were observed. The moderate aerosol optical depth in the range of 0.3 to 0.6 was found during the dust periods. The sun photometer infrared channel at the 1640 nm wavelength was used in the retrieval to investigate possible improvements to aerosol size retrievals, and it was expected to have a larger sensitivity to coarse particles. The comparison between column (aerosol optical depth) and surface (dust concentration) data demonstrates the connection between the Saharan Air Layer and the boundary layer in the Caribbean region, as is shown by the synchronized detection of the successive dust events in both datasets. However the differences of size distributions derived from sun photometer data and in situ observations reveal the difficulties in carrying out a column closure study.

scholarly journals Sun photometer retrievals of Saharan dust properties over Barbados during SALTRACE

2019 ◽  
Author(s):  
Carlos Toledano ◽  
Benjamín Torres ◽  
Cristian Velasco-Merino ◽  
Dietrich Althausen ◽  
Silke Groß ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Saharan Dust ◽  
Caribbean Region ◽  
The Sun ◽  
Concentration Data ◽  
The Caribbean ◽  
Sun Photometer ◽  
Dust Events

Abstract. The Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE) was devoted to the investigation of Saharan dust properties over the Caribbean. The campaign took place in June–July 2013. A wide set of ground-based and airborne aerosol instrumentation was deployed at Barbados island for a comprehensive experiment. Several sun photometers performed measurements during this campaign: two AERONET Cimel sun photometers and the Sun and Sky Automatic Radiometer (SSARA). The sun photometers were co-located with the ground-based multi-wavelength lidars BERTHA and POLIS. Aerosol properties derived from direct sun and sky radiance observations are analyzed, and a comparison with the co-located lidar and in-situ data is provided. The time series of aerosol optical depth allows identifying successive dust events with short periods in between in which the marine background conditions were observed. Moderate aerosol optical depth in the range 0.3 to 0.6 was found during the dust periods. The sun photometer infrared channel at 1640 nm wavelength was used in the retrieval to investigate possible improvements and expected larger sensitivity to coarse particles. The comparison between column (AOD) and surface (dust concentration) data demonstrates the connection between the Saharan Air Layer and the boundary layer in the Caribbean region, as it is shown by the synchronized detection of the successive dust events in both data sets. However the comparison of size distributions derived from sun photometer data and in-situ observations reveal the difficulties to carry out a column closure study.

Predictive distribution models of European hake in the south-central Mediterranean Sea

Hydrobiologia ◽  
2017 ◽  
Vol 821 (1) ◽  
pp. 153-172 ◽  
Author(s):  
G. Garofalo ◽  
S. Fezzani ◽  
F. Gargano ◽  
G. Milisenda ◽  
O. Ben Abdallah ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Predictive Distribution ◽  
The South ◽  
Distribution Models ◽  
Central Mediterranean ◽  
South Central ◽  
Central Mediterranean Sea ◽  
European Hake

scholarly journals Air–Sea Interaction in the Central Mediterranean Sea: Assessment of Reanalysis and Satellite Observations

2021 ◽  
Vol 13 (11) ◽  
pp. 2188
Author(s):  
Salvatore Marullo ◽  
Jaime Pitarch ◽  
Marco Bellacicco ◽  
Alcide Giorgio di Sarra ◽  
Daniela Meloni ◽  
...  
Keyword(s):  
Heat Flux ◽  
Mediterranean Sea ◽  
Seasonal Cycle ◽  
Heat Fluxes ◽  
Meteorological Variables ◽  
Central Mediterranean ◽  
High Quality ◽  
Central Mediterranean Sea ◽  
In Situ Observations

Air–sea heat fluxes are essential climate variables, required for understanding air–sea interactions, local, regional and global climate, the hydrological cycle and atmospheric and oceanic circulation. In situ measurements of fluxes over the ocean are sparse and model reanalysis and satellite data can provide estimates at different scales. The accuracy of such estimates is therefore essential to obtain a reliable description of the occurring phenomena and changes. In this work, air–sea radiative fluxes derived from the SEVIRI sensor onboard the MSG satellite and from ERA5 reanalysis have been compared to direct high quality measurements performed over a complete annual cycle at the ENEA oceanographic observatory, near the island of Lampedusa in the Central Mediterranean Sea. Our analysis reveals that satellite derived products overestimate in situ direct observations of the downwelling short-wave (bias of 6.1 W/m2) and longwave (bias of 6.6 W/m2) irradiances. ERA5 reanalysis data show a negligible positive bias (+1.0 W/m2) for the shortwave irradiance and a large negative bias (−17 W/m2) for the longwave irradiance with respect to in situ observations. ERA5 meteorological variables, which are needed to calculate the air–sea heat flux using bulk formulae, have been compared with in situ measurements made at the oceanographic observatory. The two meteorological datasets show a very good agreement, with some underestimate of the wind speed by ERA5 for high wind conditions. We investigated the impact of different determinations of heat fluxes on the near surface sea temperature (1 m depth), as determined by calculations with a one-dimensional numerical model, the General Ocean Turbulence Model (GOTM). The sensitivity of the model to the different forcing was measured in terms of differences with respect to in situ temperature measurements made during the period under investigation. All simulations reproduced the true seasonal cycle and all high frequency variabilities. The best results on the overall seasonal cycle were obtained when using meteorological variables in the bulk formulae formulations used by the model itself. The derived overall annual net heat flux values were between +1.6 and 40.4 W/m2, depending on the used dataset. The large variability obtained with different datasets suggests that current determinations of the heat flux components and, in particular, of the longwave irradiance, need to be improved. The ENEA oceanographic observatory provides a complete, long-term, high resolution time series of high quality in situ observations. In the future, more similar sites worldwide will be needed for model and satellite validations and to improve the determination of the air–sea exchange and the understanding of related processes.

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