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

Abstract. The regime of intense desert dust (DD) episodes over the broader Mediterranean Basin is studied for the period 2000–2007 at a complete spatial coverage. An objective and dynamic algorithm has been set up which uses daily measurements of various aerosol optical properties taken by different satellite databases, enabling the identification of DD episodes and their classification into strong and extreme ones. The algorithm's performance was tested against surface-based (in situ) particulate matter (PM) and (columnar) sun-photometric AERONET (AErosol RObotic NETwork) measurements from stations distributed across the Mediterranean. The comparisons have shown the reasonable ability of the algorithm to detect the DD episodes taking place within the study region. The largest disagreements with PM data were found in the western Mediterranean in summer, when African dust transport has a great vertical extent that cannot be satisfactorily captured by surface measurements. According to our results, DD episodes in the Mediterranean Basin are quite frequent (up to 11.4 episodes yr−1), while there is a significant spatial and temporal variability in their frequency of occurrence and their intensity. Strong episodes occur more frequently in the western Mediterranean Basin, whilst extreme ones appear more frequently over central Mediterranean Sea areas. Apart from this longitudinal variation, there is a predominant latitudinal variability in both frequency and intensity, with decreasing values from south to north. A significant seasonal variation was also found for the frequency of DD episodes, with both strong and extreme episodes being more frequent during summer in the western Mediterranean Basin, but during spring in its central and eastern parts. In most cases (> 85%) the Mediterranean dust episodes last a bit longer than a day on average, although their duration can reach six days for strong episodes and four days for extreme episodes. A noticeable year-to-year variability was also found, especially for the frequency of the episodes.

Sources of desertdust, atmospheric transport, recordedconcentrationsof atmospheric particulate matter (PM), physical, compositional, andbiological characteristics, and likely direct and indirect impactson air quality impairment are reviewed without a systematic, but withan expert approach. The aim is to offer information necessary to protectthe health of exposed populations in the dust-emitting and dust-receptorregions. This review corroborates the complexity of the process bywhich air quality is impaired during dust episodes, the mixture ofcomponents that PM might contain during dust episodes, the differencesbetween dust emission and reception regions, and the interplay ofindirect effects (thinning the boundary layer; concentration of localpollution; interactions with anthropogenic pollutants). Based on thesedust episode patterns, we recommend the implementation of alert systemsto protect the more vulnerable members of the population and highlighta number of recommendations for air quality monitoring during suchepisodes to provide adequate data sets to rigorously evaluate healthoutcomes associated with dust exposure in emitting and receptor regionsand the possible causes for these effects.

One specimen of live sharksucker was caught with a bottom trammel net in Taşucu Bay, south-eastern coast of Turkey, at 1 m depth on May, 2021. Meristic parameters were determined by fin ray counts and metric parameters were measured from the photos of the specimen. Excluding the recent record in Antalya Gulf, previous records of this species occurred later than May, generally in July in the Mediterranean Sea as well as in the Aegean Sea. The biometrical measurements were different in Taşucu Bay compared to those caught from the Aegean Sea and the central Mediterranean Sea (Tunisian and Sicilian waters), but relatively similar to those reported from Croatia. Major discriminative variables, albeit less significant in individuals from the central Mediterranean, were the number of anal, pectoral and dorsal fin rays. Numbers of suction disc laminae were higher in individuals from the central Mediterranean Sea and New Zealand than those from the Turkish coasts (all 21 disc laminae). The statistical analyses (Principal Component and Discriminant analyses) affirmed successful use of meristic parameters to differentiate the biometric characteristics of the species from the Aegean Sea, the central and eastern Mediterranean Sea. The length-weight relationship showed that the species had a negative allometric growth.

Monitoring the impact of desert dust outbreaks for air quality for health studies

Polyclinum constellatum is a colonial ascidian with a pantropical distribution, recently introduced in the Eastern Mediterranean Sea, indeed it was reported along Egyptian and Turkish coasts 2016 and 2018, respectively. In the present study we report its presence along the coasts of Greece and Italy (Eastern and Central Mediterranean Sea, respectively), using an integrated approach joining morphological and molecular analysis. Colonies of P. constellatum were collected from artificial substrata in the harbour of Taranto (Ionian Sea) in November 2018 and in the marina of Heraklion (Crete, Aegean Sea) in October 2019. Remarkably, several colonies observed and collected in the Heraklion marina appeared as two or more masses joined at their base or fused together, often with different colour morpho-types. Here we provide their detailed morphological description and molecular characterization using a long fragment of the mitochondrial COI sequence as DNA barcode. Furthermore, we present and discuss a comparative table of the main morphological features of all species of the genus Polyclinum known to date, and an accurate analysis of the reliability of the Polyclinum COI sequence currently available. Our study proves that P. constellatum is further spreading in the Eastern Mediterranean Sea and already reached the Central Mediterranean Sea. Moreover, the present study reveals the presence of erroneously assigned Polyclinum COI sequences in public databases and a possible synonymy between the species P. constellatum, Polyclinum indicum Sebastian, 1954 (accepted as Polyclinum sebastiani Brunetti, 2007) and Polyclinum madrasensis Sebastian, 1952. Overall, our data provide a useful tool for the accurate and reliable identification of this expanding species in other non-investigated areas and suggest the most likely vector of introduction of this non-indigenous species in the investigated localities.

Routine aerosol measurements are carried out at El Arenosillo station (37.1°N, 6.7°W), in Huelva (Spain), since February 2000 with a Cimel Sun photometer included in the AERONET network. This station, located in the coast of the southwestern Iberian Peninsula, is an appropriate site for the detection and characterization of desert dust aerosols arriving from North Africa. The aerosol database allows us to make an inventory of desert dust events over 6 years corresponding to the period 2000–2005. The inventory is based on threshold values for the aerosol optical depth (AOD) and Ångström exponent, the analysis of the size distributions, a manual inspection, and the use of air mass back trajectories as complementary information. This inventory shows the presence of desert aerosols 65 d yr−1 (18% of days), although there are significant differences among years. Desert dust events have a mean duration of 4 days, with mean AOD (440 nm) of 0.31 and mean Ångström exponent of 0.66. The desert dust episodes are more frequent in February, March, and the summer months. During autumn, winter, and April the episodes are less frequent. This seasonal pattern of the desert events influences the AOD at El Arenosillo, which presents an analogous seasonal pattern. Because of the desert events, AOD levels increase 28% at 440 nm and 48% at 870 nm. Desert dust intrusions have been also catalogued according to four basic meteorological scenarios. The analysis of the desert inventory has made it possible to establish an automatic method for the detection of the desert dust intrusions over the Iberian Peninsula with Sun photometer data. Finally, a classification of air masses (based on back trajectories) has been compared with the occurrence of desert dust intrusions.

Global warming is one of the greatest environmental, economic, and social threats in the world. There are many assessments to estimate climate variability over many regions. A change in the Earth’s surface temperature leads to increase in extreme temperature events, which are harmful to the ecosystem, and moreover, they create danger on human health. In this study, we have selected the western part of Turkey as the study area, since climate change projections for Turkey point out that the highest temperature change can be expected on this region during summer, and the Turkish population is very dense here to be affected by extreme events. We have used apparent temperatures to define the heat waves which we have determined their frequencies for the summer months (June–August) of 1965–2006. Since the regional comparisons of station results are intended, we selected the 90th percentile value for each station as a threshold value to be used in the delineation of heat waves. Then, the number of heat waves is determined by imposing the constraint that apparent temperatures stay above the threshold value at least for three consecutive days. Then, the changes in the number of hot days and heat waves and also their durations are analyzed by using the linear least square method. We have found that the number of hot days, heat waves, and heat wave durations is increased between 1965 and 2006 on the western part of Turkey. Additionally, their rate of change is larger within the last decade and extremes are frequently observed after 1998. Regional distributions show that the tendency of the number of heat wave events increases towards the southern latitudes of the domain. Moreover, we investigated the relationship between the number of hot days and the sea surface temperatures of the Mediterranean Sea and Black Sea. Correlation analyses are carried out by the number of hot days and averaged sea surface temperatures on the regions of the western, central, and eastern Mediterranean Sea and the Black Sea. It is found that the number of hot days of west Turkey is better correlated with the sea surface temperatures averaged over eastern Mediterranean and Black Seas. The number of heat waves is found significantly correlated with the fire occurrences for most of the stations.

Organic matter in sediments of canyons and open slopes of the Portuguese, Catalan, Southern Adriatic and Cretan Sea margins

Abstract. A lidar method is presented that permits the estimation of height profiles of ice nuclei concentrations (INC) in desert dust layers. The polarization lidar technique is applied to separate dust and non-dust backscatter and extinction coefficients. The desert dust extinction coefficients σd are then converted to aerosol particle number concentrations APC280 which consider particles with radius > 280 nm only. By using profiles of APC280 and ambient temperature T along the laser beam, the profile of INC can be estimated within a factor of 3 by means of APC-T-INC parameterizations from the literature. The observed close relationship between σd at 500 nm and APC280 is of key importance for a successful INC retrieval. We studied this link by means of AERONET (Aerosol Robotic Network) sun/sky photometer observations at Morocco, Cabo Verde, Barbados, and Cyprus during desert dust outbreaks. The new INC retrieval method is applied to lidar observations of dust layers with the spaceborne lidar CALIOP (Cloud Aerosol Lidar with Orthogonal Polarization) during two overpasses over the EARLINET (European Aerosol Research Lidar Network) lidar site of the Cyprus University of Technology (CUT), Limassol (34.7° N, 33° E), Cyprus. The good agreement between the CALIOP and CUT lidar retrievals of σd, APC280, and INC profiles corroborates the potential of CALIOP to provide 3-D global desert dust APC280 and INC data sets.

This paper is the companion paper of Córdoba-Jabonero et al. (2021). It deals with the estimation of the longwave (LW) and net dust direct radiative effect (DRE) during the dust episode that occurred between 23 and 30 June, 2019, and coincided with a mega-heatwave. The analysis is performed at two European sites where polarized-Micro-Pulse Lidars ran continuously to retrieve the vertical distribution of the dust optical properties: Barcelona, Spain, 23–30 June, and Leipzig, Germany, 29–30 June. The radiative effect is computed with the GAME radiative transfer model separately for the fine- and coarse-mode dust. The instantaneous and daily radiative effect and radiative efficiency (DREff) are provided for the fine-mode, coarse-mode and total dust at the surface, top of the atmosphere (TOA) and in the atmosphere. The fine-mode daily LW DRE is small (< 6 % of the shortwave (SW) component) which makes the coarse-mode LW DRE the main modulator of the total dust net DRE. The coarse-mode LW DRE starts exceeding (in absolute values) the SW component in the middle of the episode which produces positive coarse-mode net DRE at both the surface and TOA. Such an unusual tendency is attributed to increasing coarse-mode size and surface temperature along the episode. This has the effect of reducing the SW cooling in Barcelona up to the point of reaching total dust net DRE positive (+0.9 W m−2) on one occasion at the surface and quasi-neutral (−0.6 W m−2) at TOA. When adding the LW component, the total dust SW radiative efficiency is reduced by a factor 1.6 at both surface (on average over the episode, the total dust net DREff is −54.1 W m−2 τ−1) and TOA (−37.3 W m−2 τ−1). A sensitivity study performed on the surface temperature and the air temperature in the dust layer, both linked to the heatwave and upon which the LW DRE strongly depends, shows that the heatwave contributed to reduce the dust net cooling effect at the surface and that it had nearly no effect at TOA. Its subsequent effect was thus to reduce the heating of the atmosphere produced by the dust particles.

Abstract. This paper is the companion paper of Córdoba-Jabonero et al. (2021). It deals with the estimation of the long-wave (LW) and net dust direct radiative effect (DRE) during the dust episode that occurred between 23 and 30 June 2019 and was paired with a mega-heatwave. The analysis is performed at two European sites where polarized micro-pulse lidars ran continuously to retrieve the vertical distribution of the dust optical properties: Barcelona, Spain, 23–30 June, and Leipzig, Germany, 29–30 June. The radiative effect is computed with the GAME (global atmospheric model) radiative transfer model separately for the fine- and coarse-mode dust. The instantaneous and daily radiative effect and radiative efficiency (DREff) are provided for the fine-mode, coarse-mode and total dust at the surface, top of the atmosphere (TOA) and in the atmosphere. The fine-mode daily LW DRE is low (&lt; 6 % of the short-wave (SW) component), which makes the coarse-mode LW DRE the main modulator of the total net dust DRE. The coarse-mode LW DRE starts exceeding (in absolute values) the SW component in the middle of the episode, which produces positive coarse-mode net DRE at both the surface and TOA. Such an unusual tendency is attributed to increasing coarse-mode size and surface temperature throughout the episode. This has the effect of reducing the SW cooling in Barcelona up to the point of reaching total net positive dust DRE (+0.9 W m−2) on one occasion at the surface and quasi-neutral (−0.6 W m−2) at TOA. When adding the LW component, the total dust SW radiative efficiency is reduced by a factor of 1.6 at both surface (on average over the episode the total dust net DREff is −54.1 W m−2 τ−1) and TOA (−37.3 W m−2 τ−1). A sensitivity study performed on the surface temperature and the air temperature in the dust layer, both linked to the heatwave and upon which the LW DRE strongly depends, shows that the heatwave contributed to reducing the dust net cooling effect at the surface and that it had nearly no effect at TOA. Its subsequent effect was thus to reduce the heating of the atmosphere produced by the dust particles.

Isolation By Distance (IBD) signals in the deep-water rose shrimp Parapenaeus longirostris (Lucas, 1846) (Decapoda, Panaeidae) in the Mediterranean Sea

This study investigates the intra-seasonal relationship between the sea surface temperatures of the Mediterranean and Black Seas and the precipitation (SST–P) of the Anatolian peninsula. Furthermore, this study might also help to understand the underlying mechanisms behind the complex interactions between the atmosphere and ocean in the region. The study presents a time-phase relationship analysis based simply on the lagged-correlations between SST and P, utilizing a large set of daily gridded observational products for precipitation (i.e. TRMM, GPCP, E-OBS and ERA-Interim) as well as in-situ observations and satellite derived gridded SST datasets (AVHRR), aiming to show the range of the uncertainty in the data. The analysis is also extended to investigate the possible link between surface flux components (FLX; shortwave, longwave, latent and sensible heat fluxes) and precipitation over the seas. The results clearly show a significant and strong relationship at intra-seasonal time scales between the sea surface temperatures of the surrounding seas and the precipitation over the Anatolian peninsula, depending on the analyzed season and dataset. In general, the strongest SST–P relationship appears in fall season, irrespective of the analyzed dataset. In this case, the all sub-basins of the peninsula are identified to exhibit strong sensitivity to the SST of the eastern and central Mediterranean, as well as the Black Sea. The analysis also indicates a strong SST–P relationship for the eastern Mediterranean, Levantine and Black Sea regions in winter and spring, but with a slightly lower level significance. It is also revealed that the strongest SST–P and FLX–P relationship over the sea appears in the western and central Mediterranean and Black Sea region.

Geomorphic evolution of the Malta Escarpment and implications for the Messinian evaporative drawdown in the eastern Mediterranean Sea

Abstract. The direct radiative effect (DRE) during 20 intense and widespread dust outbreaks, which affected the broader Mediterranean basin over the period March 2000–February 2013, has been calculated with the NMMB-MONARCH model at regional (Sahara and European continent) and short-term temporal (84 h) scales. According to model simulations, the maximum dust aerosol optical depths (AODs) range from ∼ 2.5 to ∼ 5.5 among the identified cases. At midday, dust outbreaks locally induce a NET (shortwave plus longwave) strong atmospheric warming (DREATM values up to 285 W m−2; Niger–Chad; dust AODs up to ∼ 5.5) and a strong surface cooling (DRENETSURF values down to −337 W m−2), whereas they strongly reduce the downward radiation at the ground level (DRESURF values down to −589 W m−2 over the Eastern Mediterranean, for extremely high dust AODs, 4.5–5). During night-time, reverse effects of smaller magnitude are found. At the top of the atmosphere (TOA), positive (planetary warming) DREs up to 85 W m−2 are found over highly reflective surfaces (Niger–Chad; dust AODs up to ∼ 5.5) while negative (planetary cooling) DREs down to −184 W m−2 (Eastern Mediterranean; dust AODs 4.5–5) are computed over dark surfaces at noon. Dust outbreaks significantly affect the mean regional radiation budget, with NET DREs ranging from −8.5 to 0.5 W m−2, from −31.6 to 2.1 W m−2, from −22.2 to 2.2 W m−2 and from −1.7 to 20.4 W m−2 for TOA, SURF, NETSURF and ATM, respectively. Although the shortwave DREs are larger than the longwave ones, the latter are comparable or even larger at TOA, particularly over the Sahara at midday. As a response to the strong surface day-time cooling, dust outbreaks cause a reduction in the regional sensible and latent heat fluxes by up to 45 and 4 W m−2, respectively, averaged over land areas of the simulation domain. Dust outbreaks reduce the temperature at 2 m by up to 4 K during day-time, whereas a reverse tendency of similar magnitude is found during night-time. Depending on the vertical distribution of dust loads and time, mineral particles heat (cool) the atmosphere by up to 0.9 K (0.8 K) during day-time (night-time) within atmospheric dust layers. Beneath and above the dust clouds, mineral particles cool (warm) the atmosphere by up to 1.3 K (1.2 K) at noon (night-time). On a regional mean basis, negative feedbacks on the total emitted dust (reduced by 19.5 %) and dust AOD (reduced by 6.9 %) are found when dust interacts with the radiation. Through the consideration of dust radiative effects in numerical simulations, the model positive and negative biases for the downward surface SW or LW radiation, respectively, with respect to Baseline Surface Radiation Network (BSRN) measurements, are reduced. In addition, they also reduce the model near-surface (at 2 m) nocturnal cold biases by up to 0.5 K (regional averages), as well as the model warm biases at 950 and 700 hPa, where the dust concentration is maximized, by up to 0.4 K. However, improvements are relatively small and do not happen in all episodes because other model first-order errors may dominate over the expected improvements, and the misrepresentation of the dust plumes' spatiotemporal features and optical properties may even produce a double penalty effect. The enhancement of dust forecasts via data assimilation techniques may significantly improve the results.