scholarly journals Aerosol seasonal variability over the Mediterranean region and relative impact of maritime, continental and Saharan dust particles over the basin from MODIS data in the year 2001

2004 ◽  
Vol 4 (9/10) ◽  
pp. 2367-2391 ◽  
Author(s):  
F. Barnaba ◽  
G. P. Gobbi
Keyword(s):  
Spatial Variability ◽  
Seasonal Variability ◽  
Mediterranean Basin ◽  
Mediterranean Region ◽  
Dust Particles ◽  
Desert Dust ◽  
Modis Data ◽  
Aerosol Mass ◽  
The Mediterranean ◽  
Aerosol Type

Abstract. The one-year (2001) record of aerosol data from the space borne Moderate Resolution Imaging Spectroradiometer (MODIS) is analyzed focusing on the Mediterranean region. The MODIS aerosol optical thickness standard product (AOT at 550nm) provided over both land and ocean is employed to evaluate the seasonal and spatial variability of the atmospheric particulate over the region. Expected accuracy of the MODIS AOT is (±0.05±0.2xAOT) over land and (±0.03±0.05xAOT) over ocean. The seasonal analysis reveals a significant AOT variability all over the region, with minimum values in Winter (AOT<0.15) and maximum in Summer (AOT>0.2). The spatial variability is also found to be considerable, particularly over land. The impact of some major urban sites and industrialized areas is detectable. For the sole Mediterranean basin, a method (aerosol mask) was implemented to separate the contribution of maritime, continental and desert dust aerosol to the total AOT. Input of both continental and desert dust particles is well captured, showing North-to-South and South-to-North AOT gradients, respectively. A quantitative summary of the AOT seasonal and regional variability is given for different sectors of the Mediterranean basin. Results of this summary were also used to test the aerosol mask assumptions and indicate the method adopted to be suitable for the aerosol type selection. Estimates of the atmospheric aerosol mass load were performed employing specifically-derived mass-to-extinction efficiencies (α). For each aerosol type, a reliable mean α value was determined on the basis of both lidar measurements of extinction and aerosol models. These estimates indicate a total of 43Mtons of desert dust suspended over the basin during 2001. A comparable value is derived for maritime aerosol. Opposite to the dust case, a minor seasonal variability (within 15%) of maritime aerosol mass is found. This latter result is considered a further check of the suitability of the methodology adopted to separate, on the basis of MODIS data, the three aerosol types which dominate the Mediterranean region.

scholarly journals Aerosol seasonal variability over the Mediterranean region and relative impact of maritime, continental and Saharan dust particles over the basin from MODIS data in the year 2001

2004 ◽  
Vol 4 (4) ◽  
pp. 4285-4337 ◽  
Author(s):  
F. Barnaba ◽  
G. P. Gobbi
Keyword(s):  
Spatial Variability ◽  
Seasonal Variability ◽  
Mediterranean Basin ◽  
Mediterranean Region ◽  
Dust Particles ◽  
Desert Dust ◽  
Modis Data ◽  
Aerosol Mass ◽  
The Mediterranean ◽  
Aerosol Type

Abstract. The one-year (2001) record of aerosol data from the space borne Moderate Resolution Imaging Spectroradiometer (MODIS) was analyzed focusing on the Mediterranean region. The MODIS aerosol optical thickness standard product (AOT at 550 nm) provided over both land and ocean was employed to evaluate the seasonal and spatial variability of the atmospheric particulate over the region. Expected accuracy of the MODIS AOT is (±0.05±0.2×AOT) over land and (±0.03±0.05×AOT) over ocean. The seasonal analysis revealed a significant AOT variability all over the region, with minimum values in Winter (AOT<0.15) and maximum in Summer (AOT>0.2). The spatial variability is also found to be considerable, particularly over land. The impact of some major urban sites and industrialized areas is detectable. For the sole Mediterranean basin, a method (aerosol mask) was implemented to separate the contribution of maritime, continental and desert dust aerosol to the total AOT. Input of both continental and desert dust particles is well captured, showing, respectively, a North-to-South and a South-to-North AOT gradient. A quantitative summary of the AOT seasonal and regional variability is given for different sectors of the Mediterranean basin. Results of this summary were also used to test the aerosol mask assumptions and indicate the method adopted to be suitable for the aerosol type selection. Estimates of the atmospheric aerosol mass load were performed employing specifically-derived mass-to-extinction efficiencies (α). For each aerosol type, a reliable mean α value was determined on the basis of lidar measurements of extinction and aerosol models. These estimates indicate a total of 43 Mtons of desert dust suspended over the basin during 2001. A comparable value is derived for maritime aerosol. Opposite to the dust case, a minor seasonal variability (within 15%) of maritime aerosol mass is found. This latter result is considered a further check of the suitability of the methodology adopted to separate, on the basis of MODIS data, the three aerosol types which dominate the Mediterranean region.

scholarly journals Primary aerosol and secondary inorganic aerosol budget over the Mediterranean Basin during 2012 and 2013

2018 ◽  
Vol 18 (7) ◽  
pp. 4911-4934 ◽  
Author(s):  
Jonathan Guth ◽  
Virginie Marécal ◽  
Béatrice Josse ◽  
Joaquim Arteta ◽  
Paul Hamer
Keyword(s):  
Mediterranean Basin ◽  
Transport Model ◽  
Coastal Areas ◽  
Sea Salt ◽  
Anthropogenic Emissions ◽  
Carbonaceous Aerosols ◽  
Desert Dust ◽  
Inorganic Aerosols ◽  
The Mediterranean ◽  
The Mediterranean Basin

Abstract. In the frame of the Chemistry-Aerosol Mediterranean Experiment (ChArMEx), we analyse the budget of primary aerosols and secondary inorganic aerosols over the Mediterranean Basin during the years 2012 and 2013. To do this, we use two year-long numerical simulations with the chemistry-transport model MOCAGE validated against satellite- and ground-based measurements. The budget is presented on an annual and a monthly basis on a domain covering 29 to 47° N latitude and 10° W to 38° E longitude. The years 2012 and 2013 show similar seasonal variations. The desert dust is the main contributor to the annual aerosol burden in the Mediterranean region with a peak in spring, and sea salt being the second most important contributor. The secondary inorganic aerosols, taken as a whole, contribute a similar level to sea salt. The results show that all of the considered aerosol types, except for sea salt aerosols, experience net export out of our Mediterranean Basin model domain, and thus this area should be considered as a source region for aerosols globally. Our study showed that 11 % of the desert dust, 22.8 to 39.5 % of the carbonaceous aerosols, 35 % of the sulfate and 9 % of the ammonium emitted or produced into the study domain are exported. The main sources of variability for aerosols between 2012 and 2013 are weather-related variations, acting on emissions processes, and the episodic import of aerosols from North American fires. In order to assess the importance of the anthropogenic emissions of the marine and the coastal areas which are central for the economy of the Mediterranean Basin, we made a sensitivity test simulation. This simulation is similar to the reference simulation but with the removal of the international shipping emissions and the anthropogenic emissions over a 50 km wide band inland along the coast. We showed that around 30 % of the emissions of carbonaceous aerosols and 35 to 60 % of the exported carbonaceous aerosols originates from the marine and coastal areas. The formation of 23, 27 and 27 %, respectively of, ammonium, nitrate and sulfate aerosols is due to the emissions within the marine and coastal area.

scholarly journals Mediterranean Heathland as a Key Habitat for Fire Adaptations: Evidence from an Experimental Approach

Forests ◽  
2020 ◽  
Vol 11 (7) ◽  
pp. 748
Author(s):  
Susana Gómez-González ◽  
Maria Paniw ◽  
Mario Durán ◽  
Sergio Picó ◽  
Irene Martín-Rodríguez ◽  
...  
Keyword(s):  
Heat Shock ◽  
Seed Size ◽  
Mediterranean Basin ◽  
Fire Ecology ◽  
Mediterranean Region ◽  
Plant Evolution ◽  
Fire Adaptations ◽  
The Mediterranean ◽  
The Mediterranean Basin

Some fire ecology studies that have focused on garrigue-like vegetation suggest a weak selective pressure of fire in the Mediterranean Basin compared to other Mediterranean-type regions. However, fire-prone Mediterranean heathland from the western end of the Mediterranean Basin has been frequently ignored in the fire ecology literature despite its high proportion of pyrogenic species. Here, we explore the evolutionary ecology of seed traits in the generalist rockrose Cistus salviifolius L. (Cistaceae) aiming to ascertain the role of the Mediterranean heathland for fire adaptations in the Mediterranean Region. We performed a germination experiment to compare the relationship of seed size to (i) heat-stimulated germination, (ii) dormancy strength, and (iii) heat survival in plants from ‘high-fire’ heathland vs. ‘low-fire’ coastal shrubland. Germination after heat-shock treatment was higher in large seeds of both ‘high-fire’ and ‘low-fire’ habitats. However, dormancy was weaker in small seeds from ‘low-fire’ habitats. Finally, seed survival to heat shock was positively related to seed size. Our results support that seed size is an adaptive trait to fire in C. salviifolius, since larger seeds had stronger dormancy, higher heat-stimulated germination and were more resistant to heat shock. This seed size–fire relationship was tighter in ‘high-fire’ Mediterranean heathland than ‘low-fire’ coastal shrubland, indicating the existence of differential fire pressures and evolutionary trends at the landscape scale. These findings highlight the Mediterranean heathland as a relevant habitat for fire-driven evolution, thus contributing to better understand the role of fire in plant evolution within the Mediterranean region.

scholarly journals Jetstream and rainfall distribution in the Mediterranean region

2011 ◽  
Vol 11 (9) ◽  
pp. 2469-2481 ◽  
Author(s):  
M. Gaetani ◽  
M. Baldi ◽  
G. A. Dalu ◽  
G. Maracchi
Keyword(s):  
Mediterranean Basin ◽  
Mediterranean Region ◽  
Atlantic Region ◽  
Rainfall Distribution ◽  
The Balkans ◽  
Rainfall Anomalies ◽  
The Mediterranean ◽  
The Cross ◽  
The Impact ◽  
Two Jets

Abstract. This is a study on the impact of the jetstream in the Euro-Atlantic region on the rainfall distribution in the Mediterranean region; the study, based on data analysis, is restricted to the Mediterranean rainy season, which lasts from September to May. During this season, most of the weather systems originate over the Atlantic, and are carried towards the Mediterranean region by the westerly flow. In the upper troposphere of the Euro-Atlantic region this flow is characterized by two jets: the Atlantic jet, which crosses the ocean with a northeasterly tilt, and the African jet, which flows above the coast of North Africa. This study shows that the cross-jet circulation of the Atlantic jet favors storm activity in its exit region, while the cross-jet circulation of the African jet suppresses this kind of activity in its entrance region, with the 1st jet-stormtrack covariance mode explaining nearly 50% of the variability. It follows that the rainfall distribution downstream to these cross-jet circulations is strongly influenced by their relative positions. Specifically, in fall, rainfall is abundant in the western Mediterranean basin (WM), when the Atlantic jet is relatively strong but its northeasterly tilt is small, and the African jet is in its easternmost position. In winter, rainfall is abundant in the eastern Mediterranean basin (EM); this is when the Atlantic jet reaches the Scandinavian peninsula and the African jet is in its westernmost position. In spring, when the two jets weaken, the Atlantic jet retreats over the ocean, but the African jet stays in its winter position, rainfall is abundant in the Alpine region and in the Balkans. In addition, the covariance between precipitation and the jetstream has been evaluated. In fall, the latitudinal displacement of the Atlantic jet and the longitudinal displacement of the African jet modulate rainfall anomalies in the WM, with 38% explained covariance. In winter, the latitudinal displacement of the Atlantic jet produces rainfall anomalies in the western and central Mediterranean, with 45% explained covariance. In spring, the latitudinal displacement of the African jet produces rainfall anomalies, with 38% explained covariance.

scholarly journals Mediterranean intense desert dust outbreaks and their vertical structure based on remote sensing data

2016 ◽  
Vol 16 (13) ◽  
pp. 8609-8642 ◽  
Author(s):  
Antonis Gkikas ◽  
Sara Basart ◽  
Nikos Hatzianastassiou ◽  
Eleni Marinou ◽  
Vassilis Amiridis ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Vertical Structure ◽  
Fine Fraction ◽  
Western Mediterranean ◽  
Dust Particles ◽  
Vertical Profiles ◽  
Study Region ◽  
Desert Dust ◽  
Modis Aod ◽  
The Mediterranean

Abstract. The main aim of the present study is to describe the vertical structure of the intense Mediterranean dust outbreaks, based on the use of satellite and surface-based retrievals/measurements. Strong and extreme desert dust (DD) episodes are identified at 1°  ×  1° spatial resolution, over the period March 2000–February 2013, through the implementation of an updated objective and dynamic algorithm. According to the algorithm, strong DD episodes occurring at a specific place correspond to cases in which the daily aerosol optical depth at 550 nm (AOD550 nm) exceeds or equals the long-term mean AOD550 nm (Mean) plus two standard deviations (SD), which is also smaller than Mean+4 × SD. Extreme DD episodes correspond to cases in which the daily AOD550 nm value equals or exceeds Mean+4 × SD. For the identification of DD episodes, additional optical properties (Ångström exponent, fine fraction, effective radius and aerosol index) derived by the MODIS-Terra &amp; Aqua (also AOD retrievals), OMI-Aura and EP-TOMS databases are used as inputs. According to the algorithm using MODIS-Terra data, over the period March 2000–February 2013, strong DD episodes occur more frequently (up to 9.9 episodes year−1) over the western Mediterranean, while the corresponding frequencies for the extreme ones are smaller (up to 3.3 episodes year−1, central Mediterranean Sea). In contrast to their frequency, dust episodes are more intense (AODs up to 4.1), over the central and eastern Mediterranean Sea, off the northern African coasts. Slightly lower frequencies and higher intensities are found when the satellite algorithm operates based on MODIS-Aqua retrievals, for the period 2003–2012. The consistency of the algorithm is successfully tested through the application of an alternative methodology for the determination of DD episodes, which produced similar features of the episodes' frequency and intensity, with just slightly higher frequencies and lower intensities. The performance of the satellite algorithm is assessed against surface-based daily data from 109 sun-photometric (AERONET) and 22 PM10 stations. The agreement between AERONET and MODIS AOD is satisfactory (R = 0.505 − 0.750) and improves considerably when MODIS level 3 retrievals with higher sub-grid spatial representativeness and homogeneity are considered. Through the comparison against PM10 concentrations, it is found that the presence of dust is justified in all ground stations with success scores ranging from 68 to 97 %. However, poor agreement is evident between satellite and ground PM10 observations in the western parts of the Mediterranean, which is attributed to the desert dust outbreaks' vertical extension and the high altitude of dust presence. The CALIOP vertical profiles of pure and polluted dust observations and the associated total backscatter coefficient at 532 nm (β532 nm), indicate that dust particles are mainly detected between 0.5 and 6 km, though they can reach 8 km between the parallels 32 and 38° N in warm seasons. An increased number of CALIOP dust records at higher altitudes is observed with increased latitude, northwards to 40° N, revealing an ascending mode of the dust transport. However, the overall intensity of DD episodes is maximum (up to 0.006 km−1 sr−1) below 2 km and at the southern parts of the study region (30–34° N). Additionally, the average thickness of dust layers gradually decreases from 4 to 2 km, moving from south to north. In spring, dust layers of moderate-to-high β532 nm values ( ∼  0.004 km−1 sr−1) are detected over the Mediterranean (35–42° N), extending from 2 to 4 km. Over the western Mediterranean, dust layers are observed between 2 and 6 km, while their base height is decreased down to 0.5 km for increasing longitudes underlying the role of topography and thermal convection. The vertical profiles of CALIOP β532 nm confirm the multilayered structure of the Mediterranean desert dust outbreaks on both annual and seasonal bases, with several dust layers of variable geometrical characteristics and intensities. A detailed analysis of the vertical structure of specific DD episodes using CALIOP profiles reveals that the consideration of the dust vertical structure is necessary when attempting comparisons between columnar MODIS AOD retrievals and ground PM10 concentrations.

A warmer Mediterranean region at the Miocene to Pliocene transition

2020 ◽  
Author(s):  
Iuliana Vasiliev ◽  
Daniela Boehn ◽  
Darja Volkovskaja ◽  
Clemens Schmitt ◽  
Konstantina Agiadi ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Mediterranean Basin ◽  
Mediterranean Region ◽  
Elevated Temperatures ◽  
Sea Water ◽  
Time Interval ◽  
Time Period ◽  
Organic Biomarkers ◽  
The Mediterranean ◽  
D Values

&lt;p&gt;Between 5.97-5.33 Ma several kilometre-thick evaporite units were deposited in the Mediterranean Basin during the Messinian Salinity Crisis (MSC). The MSC reflects a period featured by a negative hydrological budget, with a net evaporative loss of water exceeding precipitation and riverine runoff. The contemporary changes in continental and marine circum-Mediterranean temperature are, however, poorly constrained. Here we reconstruct continental mean annual temperatures (MAT) using branched glycerol dialkyl glycerol tetraether (GDGT) biomarkers for the time period corresponding to MSC Stage 3 (5.55-5.33 Ma). Additionally, for the same time interval, we estimate sea surface temperatures (SSTs) of the Mediterranean Sea using isoprenoidal GDGTs based TEX&lt;sub&gt;86&lt;/sub&gt; proxy. The excellently preserved organic biomarkers were extracted from outcrops and DSDP cores spread over a large part of the onland (Malaga, Sicily, Cyprus) and offshore (holes 124 and 134 from the Balearic abyssal plane and hole 374 from the Ionian Basin) Mediterranean Basin domain. The calculated MATs for the 5.55 to 5.33 Ma interval show values around 16 to 18 &amp;#186;C for the Malaga, Sicily and Cyprus outcrops. The MAT values calculated for DSDP Leg 13 holes 124, 134 and Leg 42A hole 374 are lower, around 11 to 13 &amp;#186;C.&lt;/p&gt;&lt;p&gt;For samples where the branched and isoprenoid tetraether (BIT) index was lower than the 0.4 we could calculate TEX&lt;sub&gt;86&lt;/sub&gt; derived SSTs averaging around 27 &amp;#186;C for all sampled locations. Where available (i.e. Sicily), we compared the TEX&lt;sub&gt;86&lt;/sub&gt; derived SSTs with alkenone based, U&lt;sup&gt;k&lt;/sup&gt;&lt;sub&gt;37&lt;/sub&gt; derived SST estimates from the same samples. The TEX&lt;sub&gt;86&lt;/sub&gt; derived SST values are slightly higher than the U&lt;sup&gt;k&lt;/sup&gt;&lt;sub&gt;37&lt;/sub&gt; derived SST of 20 to 28 &amp;#186;C. For the Mediterranean region, values between 19 and 27 &amp;#186;C of the U&lt;sup&gt;k&lt;/sup&gt;&lt;sub&gt;37&lt;/sub&gt; derived SSTs were calculated for the interval between the 8.0 and 6.4 Ma (Tzanova et al., 2015), close to our calculations for Sicily section (20 to 28 &amp;#186;C). Independent of common pitfalls that may arise in using molecular biomarkers as temperature proxies, both SST estimates independently hint towards much warmer Mediterranean Sea water during the latest phase (Stage 3) of the MSC. These elevated temperatures coincide with higher &amp;#948;D values measured on alkenones and long chain n-alkanes (both records indicating for more arid and/or warmer conditions than today between 5.55 and 5.33 Ma). We therefore conclude that the climate between 5.55 to 5.33 Ma was warmer than present-day conditions, recorded both in the Mediterranean Sea and the land surrounding it.&lt;/p&gt;

scholarly journals Dust aerosol radiative effects during summer 2012 simulated with a coupled regional aerosol–atmosphere–ocean model over the Mediterranean

2015 ◽  
Vol 15 (6) ◽  
pp. 3303-3326 ◽  
Author(s):  
P. Nabat ◽  
S. Somot ◽  
M. Mallet ◽  
M. Michou ◽  
F. Sevault ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Mediterranean Region ◽  
Short Wave ◽  
Ocean Model ◽  
Dust Particles ◽  
Radiative Effects ◽  
Aerosol Radiative Forcing ◽  
Dust Aerosols ◽  
The Mediterranean ◽  
Aerosol Radiative

Abstract. The present study investigates the radiative effects of dust aerosols in the Mediterranean region during summer 2012 using a coupled regional aerosol–atmosphere–ocean model (CNRM-RCSM5). A prognostic aerosol scheme, including desert dust, sea salt, organic, black-carbon and sulphate particles, has been integrated to CNRM-RCSM5 in addition to the atmosphere, land surface and ocean components. An evaluation of this aerosol scheme of CNRM-RCSM5, and especially of the dust aerosols, has been performed against in situ and satellite measurements, showing its ability to reproduce the spatial and temporal variability of aerosol optical depth (AOD) over the Mediterranean region in summer 2012. The dust vertical and size distributions have also been evaluated against observations from the TRAQA/ChArMEx campaign. Three simulations have been carried out for summer 2012 with CNRM-RCSM5, including the full prognostic aerosol scheme, only monthly-averaged AOD means from the aerosol scheme or no aerosols at all, in order to focus on the radiative effects of dust particles and the role of the prognostic scheme. Surface short-wave aerosol radiative forcing variability is found to be more than twice as high over regions affected by dust aerosols, when using a prognostic aerosol scheme instead of monthly AOD means. In this case downward surface solar radiation is also found to be better reproduced according to a comparison with several stations across the Mediterranean. A composite study over 14 stations across the Mediterranean, designed to identify days with high dust AOD, also reveals the improvement of the representation of surface temperature brought by the use of the prognostic aerosol scheme. Indeed the surface receives less radiation during dusty days, but only the simulation using the prognostic aerosol scheme is found to reproduce the observed intensity of the dimming and warming on dusty days. Moreover, the radiation and temperature averages over summer 2012 are also modified by the use of prognostic aerosols, mainly because of the differences brought in short-wave aerosol radiative forcing variability. Therefore this first comparison over summer 2012 highlights the importance of the choice of the representation of aerosols in climate models.

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