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A rare event of mixed biomass-burning and polluted dust aerosols was observed over Athens, Greece (37.9° N, 23.6° E), during 21–26 May 2014. This event was studied using a synergy of a 6-wavelength elastic-Raman-depolarization lidar measurements, a CIMEL sun photometer, and in situ instrumentation. The FLEXPART dispersion model was used to identify the aerosol sources and quantify the contribution of dust and black carbon particles to the mass concentration. The identified air masses were found to originate from Kazakhstan and Saharan deserts, under a rare atmospheric pressure system. The lidar ratio (LR) values retrieved from the Raman lidar ranged within 25–89 sr (355 nm) and 35–70 sr (532 nm). The particle linear depolarization ratio (δaer) ranged from 7 to 28% (532 nm), indicating mixing of dust with biomass-burning particles. The aerosol optical depth (AOD) values derived from the lidar ranged from 0.09–0.43 (355 nm) to 0.07–0.25 (532 nm). An inversion algorithm was used to derive the mean aerosol microphysical properties (mean effective radius (reff), single scattering albedo (SSA), and mean complex refractive index (m)) inside selected atmospheric layers. We found that reff was 0.12–0.51 (±0.04) µm, SSA was 0.94–0.98 (±0.19) (at 532 nm), while m ranged between 1.39 (±0.05) + 0.002 (±0.001)i and 1.63 (±0.05) + 0.008 (±0.004)i. The polarization lidar photometer networking (POLIPHON) algorithm was used to estimate the vertical profile of the mass concentration for the dust and non-dust components. A mean mass concentration of 15 ± 5 μg m−3 and 80 ± 29 μg m−3 for smoke and dust was estimated for selected days, respectively. Finally, the retrieved aerosol microphysical properties were compared with column-integrated sun photometer CIMEL data with good agreement. [ABSTRACT FROM AUTHOR]

Accurate continuous measurements of relative humidity (RH) vertical profiles in the lower troposphere have become a significant scientific challenge. In recent years a synergy of various ground-based remote sensing instruments have been successfully used for RH vertical profiling, which has resulted in the improvement of spatial resolution and, in some cases, of the accuracy of the measurement. Some studies have also suggested the use of highresolution model simulations as input datasets into RH vertical profiling techniques. In this paper we apply two synergetic methods for RH profiling, including the synergy of lidar with a microwave radiometer and high-resolution atmospheric modeling. The two methods are employed for RH retrieval between 100 and 6000m with increased spatial resolution, based on datasets from the HygrA-CD (Hygroscopic Aerosols to Cloud Droplets) campaign conducted in Athens, Greece from May to June 2014. RH profiles from synergetic methods are then compared with those retrieved using single instruments or as simulated by high-resolution models. Our proposed technique for RH profiling provides improved statistical agreement with reference to radiosoundings by 27% when the lidar–radiometer (in comparison with radiometer measurements) approach is used and by 15% when a lidar model is used (in comparison with WRF-model simulations). Mean uncertainty of RH due to temperature bias in RH profiling was ~ 4:34% for the lidar–radiometer and ~ 1:22% for the lidar–model methods. However, maximum uncertainty in RH retrievals due to temperature bias showed that lidar-model method is more reliable at heights greater than 2000 m. Overall, our results have demonstrated the capability of both combined methods for daytime measurements in heights between 100 and 6000m when lidar–radiometer or lidar–WRF combined datasets are available. [ABSTRACT FROM AUTHOR]

Vertical profiling of aerosol particles was performed during the PANhellenic infrastructure for Atmospheric Composition and climatE chAnge (PANACEA) winter campaign (10 January 2020–7 February 2020) over the city of Ioannina, Greece (39.65° N, 20.85° E, 500 m a.s.l.). The middle-sized city of Ioannina suffers from wintertime air pollution episodes due to biomass burning (BB) domestic heating activities. The lidar technique was applied during the PANACEA winter campaign on Ioannina city, to fill the gap of knowledge of the spatio-temporal evolution of the vertical mixing of the particles occurring during these winter-time air pollution episodes. During this campaign the mobile single-wavelength (532 nm) depolarization Aerosol lIdAr System (AIAS) was used to measure the spatio-temporal evolution of the aerosols' vertical profiles within the Planetary Boundary Layer (PBL) and the lower free troposphere (LFT; up to 4 km height a.s.l.). AIAS performed almost continuous lidar measurements from morning to late evening hours (typically from 07:00 to 19:00 UTC), under cloud-free conditions, to provide the vertical profiles of the aerosol backscatter coefficient (baer) and the particle linear depolarization ratio (PLDR), both at 532 nm. In this study we emphasized on the vertical profiling of very fresh (~hours) biomass burning (BB) particles originating from local domestic heating activities in the area. In total, 33 out of 34 aerosol layers in the lower free troposphere were characterized as fresh biomass burning ones of local origin, showing a mean particle linear depolarization value of 0.04 ± 0.02 with a range of 0.01 to 0.09 (532 nm) in a height region 1.21–2.23 km a.s.l. To corroborate our findings, we used in situ data, particulate matter (PM) concentrations (PM2.5) from a particulate sensor located close to our station, and the total black carbon (BC) concentrations along with the respective contribution of the fossil fuel (BCff) and biomass/wood burning (BCwb) from the Aethalometer. The PM2.5 mass concentrations ranged from 5.6 to 175.7 μg/m3, while the wood burning emissions from residential heating were increasing during the evening hours, with decreasing temperatures. The BCwb concentrations ranged from 0.5 to 17.5 μg/m3, with an extremely high mean contribution of BCwb equal to 85.4%, which in some cases during night-time reached up to 100% during the studied period. [ABSTRACT FROM AUTHOR]

Mean optical and microphysical aerosol properties of long-range transported biomass burning (BB) particles and mixtures are presented from a 9-year (2011–2019) data set of multiwavelength Raman lidar data, obtained by the EOLE lidar over the city of Athens (37.58° N, 23.47° E), Greece. We studied 34 aerosol layers characterized as: (1) smoke; (2) smoke + continental polluted, and (3) smoke + mixed dust. We found, mainly, small-sized aerosols with mean backscatter-related (355 nm/532 nm, 532 nm/1064 nm) values and Ångström exponent (AE) values in the range 1.4–1.7. The lidar ratio (LR) value at 355 nm was found to be 57 ± 10 sr, 51 ± 5 sr, and 38 ± 9 sr for the aerosol categories (1), (2), and (3), respectively; while at 532 nm, we observed LR values of 73 ± 11 sr, 59 ± 10 sr, and 62 ± 12 for the same categories. Regarding the retrieved microphysical properties, the effective radius (reff) ranged from 0.24 ± 0.11 to 0.24 ± 0.14 μm for all aerosol categories, while the volume density (vd) ranged from 8.6 ± 3.2 to 20.7 ± 14.1 μm−3cm−3 with the higher values linked to aerosol categories (1) and (2); the real part of the refractive index (mR) ranged between 1.49 and 1.53, while for the imaginary part (mI), we found values within 0.0108 i and 0.0126 i. Finally, the single scattering albedo (SSA) of the propped particles varied from 0.915 to 0.936 at all three wavelengths (355–532–1064 nm). The novelty of this study is the provision of typical values of BB aerosol properties from the UV to the near IR, which can be used in forecasting the aerosol climatic effects in the European region. [ABSTRACT FROM AUTHOR]

A backscattering lidar system, the first of this kind in Brazil, has been used to provide the vertical profile of the aerosol backscatter coefficient at 532 nm up to an altitude of 4–6 km above sea level (ASL), in a suburban area in the city of São Paulo. The lidar system has been operational since September 2001. The lidar data products were obtained in a 4-yr period (2001–04) and concerned the aerosol optical thickness (AOT), the aerosol backscattering and extinction coefficients at 532 nm, cloud properties (cloud base, thickness), planetary boundary layer (PBL) heights, aerosol layering, and the structure and dynamics of the lower troposphere. The lidar data are presented and analyzed in synergy with AOT measurements obtained by a Cimel sun-tracking photometer in the visible spectral region, not only to validate the lidar data but also to provide an input value of the so-called extinction-to-backscatter ratio [lidar ratio (LR)]. A correlation between the lidar data and the data obtained by a Cimel sun-tracking photometer [belonging to the Aerosol Robotic Network (AERONET)] is being made to set a temporal database of those data that were collected concomitantly and to cross correlate the information gathered by each instrument. The sun photometer data are used to provide AOT values at selected wavelengths and thus to derive the Ångström exponent (AE) values, single scattering albedo (SSA) and phase function values, and LR values. The analysis of these data showed an important trend in the seasonal signature of the LR indicating a change of the predominant type of aerosol between the dry and wet seasons. Thus, during the wet season the LR lidar values are greater (50–60 sr), which indicates that larger absorption by the aerosols takes place during this period. The corresponding AE values range between 1.3 and 2 for both periods. [ABSTRACT FROM AUTHOR]

The PANhellenic infrastructure for Atmospheric Composition and climate change (PANACEA) campaign took place in July 2019, to assess the presence of aerosols both in situ and at different heights, in selected cities of Greece suffering from high air pollution levels. One of these sites was the city of Volos (39.21° N., 22.57° E). Vertical profiles of the aerosol backscatter coefficient (b aer) and the particle linear depolarization ratio (δ p) of maritime polluted, urban, smoke and dust mixtures were measured during using the mobile depolarization Aerosol lIdAr System (AIAS). 42 aerosol layers were characterized, out of which 40% were of urban origin, 26% of smoke origin, 21% maritime polluted aerosol layers and 12% dust mixtures. The maritime polluted and urban aerosols showed a mean δ p value at 532 nm of 4 ± 1%, within a range of 2–6% and 2–5%, respectively. The smoke aerosols showed a mean δ p value of 6 ± 1%, within a range of 3–9%, while the dust mixtures showed a mean δ p of 20 ± 4%, ranging from 13 to 29%. Finally, the majority of these layers were observed above 250 up to 2000 m height asl., although the dust mixtures reached 3000 m height asl. • Vertical profiles of the b aer and the δ p of maritime polluted, urban, smoke and dust mixture aerosols. • The maritime polluted and urban aerosols showed a mean δ p at 532 nm of 4±1 %, within a range of 2-6 % and 2-5 %, respectively. • The smoke aerosols showed a mean δ p value of 6±1 %, within a range of 3-9 %. • The dust mixtures showed a mean δ p of 20±4 %, ranging from 13 to 29 %. [ABSTRACT FROM AUTHOR]

We investigate the temporal evolution of the planetary boundary-layer (PBL) height over the basin of Athens, Greece, during a 6-year period (2011–2016), using data from a Raman lidar system. The range-corrected lidar signals are selected around local noon (1200 UTC) and midnight (0000 UTC), for a total of 332 cases: 165 days and 167 nights. In this dataset, the extended-Kalman filtering technique is applied and tested for the determination of the PBL height. Several well-established techniques for the PBL height estimation based on lidar data are also tested for a total of 35 cases. The lidar-derived PBL heights are compared to those derived from radiosonde data. The mean PBL height over Athens is found to be 1617 ± 324 m at 1200 UTC and 892 ± 130 m at 0000 UTC for the period examined, while the mean PBL-height growth rate is found to be 170 ± 64 m h−1 and 90 ± 17 m h−1 during daytime and night-time, respectively. [ABSTRACT FROM AUTHOR]

Since 2018, the Aeolus satellite of the European Space Agency (ESA) has acquired wind HLOS (horizontal line-of-sight) profiles throughout the troposphere and up to the lower stratosphere, filling a critical gap in the Global Observing System (GOS). Aeolus, carrying ALADIN (Atmospheric LAser Doppler INstrument), the first UV HSRL (High Spectral Resolution Lidar) Doppler lidar ever placed in space, provides also vertically resolved optical properties of particulates (aerosols and clouds). The present study focuses on the assessment of Aeolus L2A particulate backscatter coefficient (baseline 2A11), retrieved by the Standard Correct Algorithm (SCA), in the eastern Mediterranean, a region hosting a variety of aerosol species. Ground-based retrievals acquired by lidar instruments operating in Athens (central Greece), Thessaloniki (northern Greece) and Antikythera (southwestern Greece) serve as reference. All lidar stations provide routine measurements to the PANACEA (PANhellenic infrastructure for Atmospheric Composition and climatE chAnge) network. A set of ancillary data, including sun-photometric observations (AERONET), reanalysis products (CAMS and MERRA-2), satellite observations (MSG-SEVIRI and MODIS Aqua) and backward-trajectories modelling (FLEXPART), is utilized towards an optimum characterization of the probed atmospheric conditions under the absence of a classification scheme in Aeolus SCA profiles. First, emphasis is given on the assessment of Aeolus SCA backscatter coefficient under specific aerosol scenarios over Antikythera island. Due to the misdetection of the cross-polar component of the backscattered lidar signal, Aeolus underestimates the aerosol backscatter coefficient by up to 33 % when non-spherical mineral particles are recorded (10 July 2019). A good performance is revealed on 3 July 2019, when horizontally homogeneous loads of fine spherical particles are confined below 4 km. For other two cases (8 July 2020 and 5 August 2020), due to noise issues, the SCA performance degrades in terms of depicting the stratification of aerosol layers composed of particles of different origin. According to the statistical assessment analysis of 43 identified cases, a poor-to-moderate performance is revealed for the unfiltered (aerosols plus clouds) SCA profiles, which improves substantially when cloud-contaminated profiles are excluded from the collocated sample. This improvement is evident at both Aeolus vertical scales (regular scales have 24 bins and mid-bin scales have 23 bins), and it is justified by the drastic reduction in the bias (from 0.45 to 0.27 Mm -1 sr -1 for SCA and from 0.69 to 0.37 Mm -1 sr -1 for SCA mid-bin) and root mean square error (from 2.00 to 1.65 Mm -1 sr -1 for SCA and from 1.88 to 1.00 Mm -1 sr -1 for SCA mid-bin) scores. In the vertical, the SCA performance degrades at the lowermost bins due to either the contamination from surface signals or the increased noise levels for the aerosol retrievals. Among the three PANACEA stations, the best agreement is found at the remote site of Antikythera with respect to the urban sites of Athens and Thessaloniki. Finally, all key Cal/Val (calibration and validation) aspects necessary for future relevant studies, the recommendations for a possible Aeolus follow-on mission and an overview of the ongoing related activities are thoroughly discussed. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the correlation between fundus autofluorescence (FAF) and spectral-domain OCT (SD-OCT) morphological analysis in eyes with acute central serous chorioretinopathy (CSCR). Methods: Thirty-one patients with a first episode of CSCR and symptom duration of less than 6 weeks were prospectively enrolled. FAF and SD-OCT examination were performed at baseline and at 2-month intervals. Main outcome measure was the correlation between FAF and SD-OCT retinal morphology. Results: At baseline, 30/31 and 29/31 eyes showed a macular hypo-AF, corresponding to the neurosensory retinal detachment (SRD), on shortwave-FAF (SW-FAF) and near-infrared-FAF (NIR-FAF), respectively. While the SRD resolved, both FAF techniques showed a granular hyper-AF in 31 eyes. At first examination, SD-OCT confirmed the SRD with a photoreceptor outer-segment (OS) elongation in all cases. During SRD resolution, the photoreceptor layer appeared thicker and fragmented. Multiple hyper-reflective precipitates were detected in the outer plexiform and nuclear layer and between the photoreceptors and appeared colocalized with the hyper-AF dots composing the granular hyper-AF. After SRD resolution, the hypo-AF area reverted to a normal pattern on SW-FAF in all eyes and in 25/31 on NIR-FAF. Examination at 12 months showed that the granular hyper-AF was still detectable in 54 % eyes, whereas 6/31 eyes showed hypo-AF dots on NIR-FAF. On SD-OCT, the junction IS/OS was identifiable in 11/31 eyes soon after the SRD resolution and appeared completely restored in all patients at the final visit. Conclusion: The simultaneous acquisition of FAF and SD-OCT provides detailed findings of retinal abnormalities of CSCR and may help to understand the evolving process linked to CSCR. [ABSTRACT FROM AUTHOR]

Since 2018, the Aeolus satellite of the European Space Agency (ESA) acquires wind HLOS (horizontal line-of-sight) profiles throughout the troposphere and up to the lower stratosphere, filling a critical gap of the Global Observing System (GOS). Aeolus, carrying ALADIN, the first UV HSRL Doppler lidar ever placed in space, along with wind HLOS profiles provides also vertically resolved optical properties of particulates (aerosols, hydrometeors). The present study focuses on the assessment of Aeolus L2A particulate backscatter coefficient, retrieved by the Standard Correct Algorithm (SCA), in the Eastern Mediterranean, a region hosting a variety of aerosol species. Ground-based retrievals acquired by lidar instruments operating in Athens (capital of Greece), Thessaloniki (north Greece) and Antikythera (southwest Greece) serve as reference. All lidar stations provide routine measurements to the PANACEA (PANhellenic infrastructure for Atmospheric Composition and climatE chAnge) network. A set of ancillary data including sunphotometric observations (AERONET), reanalysis products (CAMS, MERRA-2), satellite observations (MSG-SEVIRI, MODIS-Aqua) and backward trajectories (FLEXPART) are utilized towards an optimum characterization of the probed atmospheric conditions under the absence of a classification scheme in Aeolus profiles. First, emphasis is given on the assessment of Aeolus L2A backscatter coefficient under different aerosol scenarios over Antikythera island. Due to the misdetection of the cross-polar component of the backscattered lidar signal, Aeolus underestimates backscatter by up to 33% when non-spherical mineral particles are recorded (10th July 2019). A very good performance is revealed on 3rd July 2019, when homogeneous loads of fine spherical particles are confined below 4 km. The level of agreement between spaceborne and ground-based retrievals varies with altitude when aerosol layers, composed of particles of different origin, are stratified (8th July 2020, 5th August 2020). According to the statistical assessment analysis for 46 identified cases, it is revealed a poor-to- moderate performance for the unfiltered (aerosols plus clouds) Aeolus profiles which improves substantially when cloud contaminated profiles are excluded from the collocated sample. This positive tendency is evident at both Aeolus vertical scales (regular, 24 bins and mid-bin, 23 bins) and it is justified by the drastic reduction of the bias and root-mean-square-error scores. In vertical, Aeolus performance downgrades at the lowermost bins (attributed to either the surface reflectance or the increased noise levels for the Aeolus retrievals and to the overlap issues for the ground-based profiles). Among the three PANACEA stations, the best agreement is found at the remote site of Antikythera with respect to the urban sites of Athens and Thessaloniki. Finally, all key Cal/Val aspects necessary for future relevant studies, the recommendations for a possible Aeolus follow-on mission and an overview of the ongoing related activities are thoroughly discussed. [ABSTRACT FROM AUTHOR]

In the present study, we present the aerosol optical properties and radiative forcing (RF) of the tropospheric and stratospheric smoke layers, observed by the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite, during the extraordinary Australian biomass burning (BB) event in 2019–2020. These BB layers were studied and analyzed within the longitude range 140° E–20° W and the latitude band 20°–60° S, as they were gradually transported from the Australian banks to the South American continent. These layers were found to be trapped within the Andes circulation, staying for longer time periods in the same longitude region. The BB aerosols reached altitudes even up to 22 km amsl., and regarding their optical properties, they were found to be nearly spherical (particle linear depolarization ratio (PLDR) < 0.10) in the troposphere; while, in the stratosphere, they were more depolarizing with PLDR values reaching up to 0.20. Fine and ultrafine smoke particles were dominant in the stratosphere, according to the observed Ångström exponent, related to the backscatter coefficients obtained by the pair of wavelengths 532 and 1064 nm (Åb up to 3), in contrast to the Åb values in the troposphere (Åb < 1) indicative of the presence of coarser particles. As the aerosols fend off the source, towards North America, a slightly descending trend was observed in the tropospheric Åb values, while the stratospheric ones were lightly increased. A maximum aerosol optical depth (AOD) value of 0.54 was recorded in the lower troposphere over the fire spots, while, in the stratosphere, AOD values up to 0.29 were observed. Sharp changes of carbon monoxide (CO) and ozone (O3) concentrations were also recorded by the Copernicus Atmosphere Monitoring Service (CAMS) in various atmospheric heights over the study region, associated with fire smoke emissions. The tropospheric smoke layers were found to have a negative mean radiative effect, ranging from −12.83 W/m2 at the top of the atmosphere (TOA), to −32.22 W/m2 on the surface (SRF), while the radiative effect of the stratospheric smoke was estimated between −7.36 at the TOA to −18.51 W/m2 at the SRF. [ABSTRACT FROM AUTHOR]

Aim: To evaluate the agreement between fluorescein angiography (FA) and spectral-domain optical coherence tomography (SD-OCT) in detecting myopic choroidal neovascularization (CNV) activity during bevacizumab treatment. Methods: Thirty-four patients with subfoveal myopic CNV were prospectively enrolled. FA and SD-OCT were performed at baseline and at all planned monthly visits. After the first injection, additional treatments were administered following detection of fluid on SD-OCT and/or leakage on FA. κ-Analysis was performed to examine the agreement between FA and SD-OCT. Results: At baseline, FA and SD-OCT agreed in 26/34 cases (κ = 0.23); sensitivity and specificity were 77.4 and 66.7%, respectively. Seven eyes presented leakage on FA with no fluid on SD-OCT, 1 case showed intraretinal fluid on SD-OCT and no leakage on FA. At the 1-month examination, specificity and κ-value improved, and 30/34 cases showed complete concordance. At the 3- and 4-month examinations, a discordance was noted in 6 cases. From the 5-month examination on, a correspondence was achieved in at least 30/34 cases and reached a perfect match in 11 sessions. Conclusions: Our study confirms the key role of FA in diagnosing myopic CNV. It seems possible there may be a role for SD-OCT in assisting FA to monitor the myopic CNV activity during anti-vascular endothelial growth factor antibody treatment. © 2014 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

In this study we present the role of the Planetary Boundary Layer Height (PBLH) on the air pollutant concentrations measured at an urban background station at the megacity of Athens, Greece, an area characterized by complex topography. For this purpose, we utilized in situ measurements of aerosol number concentrations at different size bins (10–200 nm) N 10-200nm , (200–550 nm) N 200-550nm , equivalent Black Carbon (eBC), and wind speed data, for the period of May – July 2020. According to our analysis, both horizontal transport and vertical mixing and dispersion of air pollutants play a critical role in air quality. More precisely, PBLH is negatively correlated with aerosol concentration. The increase in the height of the Planetary Boundary Layer (PBL) favors a reduction in aerosol concentration, which, to some extent, compensates for the increase in aerosol load due to emission sources and horizontal transport from the city center. The horizontal advection process is related to the PBLH, since a deep PBL drives the advection, while a shallow PBL is characterized by weak horizontal wind velocities. On the other hand, under stagnant air mass conditions, when the PBL shrinks, the concentrations of air pollutants increase. On average, a 25% increase in the PBLH results in a 15% reduction in aerosol concentration, whereas a 15% reduction in the PBLH may result in a 10% increase in aerosol concentrations. Overall, N 10-200nm particle concentrations increases, when air masses arrive from the S-NW sector (city center) due to traffic and vehicle emissions, while transport of continental pollution mixed with local and regional emissions along the Balkans-Aegean Sea axis, is originating from the NE axis under high wind speeds. The latter is more clearly recognized from aged aerosol components such as sulphate. Whereas, the N 200-550nm and eBC showed increased concentration load under stagnant air mass conditions, independently of the wind direction. [Display omitted] • Horizontal transport, vertical mixing and dispersion of air pollutants play a critical role in air quality. • PBLH is negatively correlated with aerosol concentration. • The increase in the height of the PBL favors a reduction in aerosol concentration, • Under stagnant air mass conditions, when the PBL shrinks, the concentrations of air pollutants increase. [ABSTRACT FROM AUTHOR]

PURPOSE: To assess the effects of intravitreal ranibizumab injection in patients affected by pigment epithelial detachment associated with occult subfoveal choroidal neovascularization. DESIGN: Prospective, interventional case series. METHODS: Participants: Forty eyes of 40 patients were considered for the purpose of the study. Consecutive patients were recruited for a 24-month study. All patients underwent a complete ophthalmic examination, including best-corrected visual acuity on Early Treatment Diabetic Retinopathy Study (ETDRS) charts. After a 3-monthly loading phase, further intravitreal ranibizumab injections were administered on the basis of detection of any type of fluid on optical coherence tomography. Primary outcome measures: Changes in mean best-corrected visual acuity at 12 and 24 months and the proportion of eyes losing fewer than 15 letters (corresponding to 3 ETDRS lines) from baseline visual acuity. Secondary outcome measures: Changes in central macular thickness on optical coherence tomography and variation in mean area of the entire lesion. RESULTS: Forty patients were included. Mean bestcorrected visual acuity decreased from 20/66 (58 ETDRS letters) to 20/83 (53 letters) at 12 months and 20/112 (489 ETDRS letters) at 24 months (P [ .003). Eighty percent and 67.5% of eyes lost fewer than 3 lines at 12 and 24 months, respectively. Mean central macular thickness passed from 545 mm to 428 mm at 12 months and 426 mm at 24 months. Mean lesion area changed from 6826 mm2 to 6312 mm2 at 12 months and 6010 mm2 at 24 months. CONCLUSIONS: The treatment of pigment epithelial detachment associated with occult subfoveal choroidal neovascularization with intravitreal ranibizumab injection after a 3-monthly loading phase and pro re nata strategy can lead to partial results over a 24-month follow-up. Further investigations are warranted to establish the best therapeutic approach to this disease. [ABSTRACT FROM AUTHOR]

In this study, we report on the retrieval of aerosol extinction profiles from ground-based scattered sunlight multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements, carried out at Athens, Greece. It is the first time that aerosol profiles are retrieved from MAX-DOAS measurements in Athens. The reported aerosol vertical distributions at 477 nm are derived from the oxygen dimer (O4) differential-slant-column-density observations at different elevation angles by applying the BRemen Optimal estimation REtrieval for Aerosol and trace gaseS (BOREAS) retrieval algorithm. Four case studies have been selected for validation purposes; the retrieved aerosol profiles and the corresponding aerosol optical depths (AODs) from the MAX-DOAS are compared with lidar extinction profiles and with sun-photometric measurements (Aerosol Robotic Network, AERONET, observations), respectively. Despite the different approach of each method regarding the retrieval of the aerosol information, the comparison with the lidar measurements at 532 nm reveals a very good agreement in terms of vertical distribution, with r>0.90 in all cases. The AODs from the MAX-DOAS and the sun photometer (the latter at 500 nm) show a satisfactory correlation (with 0.45 < r < 0.7 in three out of the four cases). The comparison indicates that the MAX-DOAS systematically underestimates the AOD in the cases of large particles (small Ångström exponent) and for measurements at small relative azimuthal angles between the viewing direction and the sun. Better agreement is achieved in the morning, at large relative azimuthal angles. Overall, the aerosol profiles retrieved from MAX-DOAS measurements are of good quality; thus, new perspectives are opened up for assessing urban aerosol pollution on a long-term basis in Athens from continuous and uninterrupted MAX-DOAS measurements. [ABSTRACT FROM AUTHOR]

The aim of this paper is to study the spatio-temporal evolution of a long-lasting Canadian biomass burning event that affected Europe in August 2018. The event produced biomass burning aerosol layers which were observed during their transport from Canada to Europe from the 16 to the 26 August 2018 using active remote sensing data from the space-borne system Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO). The total number of aerosol layers detected was 745 of which 42% were identified as pure biomass burning. The remaining 58% were attributed to smoke mixed with: polluted dust (34%), clean continental (10%), polluted continental (5%), desert dust (6%) or marine aerosols (3%). In this study, smoke layers, pure and mixed ones, were observed by the CALIPSO satellite from 0.8 and up to 9.6 km height above mean sea level (amsl.). The mean altitude of these layers was found between 2.1 and 5.2 km amsl. The Ångström exponent, relevant to the aerosol backscatter coefficient (532/1064 nm), ranged between 0.9 and 1.5, indicating aerosols of different sizes. The mean linear particle depolarization ratio at 532 nm for pure biomass burning aerosols was found equal to 0.05 ± 0.04, indicating near spherical aerosols. We also observed that, in case of no aerosol mixing, the sphericity of pure smoke aerosols does not change during the air mass transportation (0.05–0.06). On the contrary, when the smoke is mixed with dessert dust the mean linear particle depolarization ratio may reach values up to 0.20 ± 0.04, especially close to the African continent (Region 4). [ABSTRACT FROM AUTHOR]

In this study, we report on the retrieval of aerosol extinction profiles from ground-based scattered sunlight multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements, carried out at Athens, Greece. It is the first time that aerosol profiles are retrieved from MAX-DOAS measurements in Athens. The reported aerosol vertical distributions at 477 nm are derived from the oxygen dimer (O4) differential slant column density observations at different elevation angles by applying the BOREAS retrieval algorithm. Four case studies have been selected for validation purposes; the retrieved aerosol profiles and the corresponding aerosol optical depths (AODs) from the MAX-DOAS are compared with lidar extinction profiles and with sun photometric measurements (AERONET observations), respectively. Despite the different approach of each method regarding the retrieval of the aerosol information, the comparison with the lidar measurements at 532 nm reveals a very good agreement in terms of vertical distribution, with r > 0.85 in all cases. The AODs from the MAX-DOAS and the sun-photometer (the latter at 500 nm) show a satisfactory correlation (with r ≈ 0.6 in three out of the four cases). The comparison indicates that the MAX-DOAS systematically underestimates the AOD in the cases of large particles (small Ångström exponent) and for measurements at small relative azimuthal angles between the viewing direction and the Sun. Better agreement is achieved in the morning, at large relative azimuthal angles. Overall, the aerosol profiles retrieved from MAX-DOAS measurements are of good quality; thus, new perspectives are opened up for assessing urban aerosol pollution on a long term-basis in Athens from continuous and uninterrupted MAX-DOAS measurements. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented regarding the use of a new algorithm for treatment of myopic choroidal neovascularization using intravitreal ranibizumab.

Particle depolarization ratio retrieved from lidar measurements are commonly used for aerosol-typing studies, microphysical inversion, or mass concentration retrievals. The particle depolarization ratio is one of the primary parameters that can differentiate several major aerosol components but only if the measurements are accurate enough. The accuracy related to the retrieval of particle depolarization ratios is the driving factor for assessing and improving the uncertainties of the depolarization products. This paper presents different depolarization calibration procedures used to improve the quality of the depolarization data. The results illustrate a significant improvement of the depolarization lidar products for all the selected lidar stations that have implemented depolarization calibration procedures. The calibrated volume and particle depolarization profiles at 532 nm show values that fall within a range that is generally accepted in the literature. [ABSTRACT FROM AUTHOR]

Measurements of cloud condensation nuclei (CCN) concentrations (cm-3) at five levels of supersaturation between 0.2–1%, together with remote sensing profiling and aerosol size distributions, were performed at an urban background site of Athens during the Hygroscopic Aerosols to Cloud Droplets (HygrA-CD) campaign. The site is affected by local emissions and long-range transport, as portrayed by the aerosol size, hygroscopicity and mixing state. Application of a state-of-the-art droplet parameterization is used to link the observed size distribution measurements, bulk composition, and modeled boundary layer dynamics with potential supersaturation, droplet number, and sensitivity of these parameters for clouds forming above the site. The sensitivity is then used to understand the source of potential droplet number variability. We find that the importance of aerosol particle concentration levels associated with the background increases as vertical velocities increase. The updraft velocity variability was found to contribute 58–90% (68.6% on average) to the variance of the cloud droplet number, followed by the variance in aerosol number (6–32%, average 23.2%). Therefore, although local sources may strongly modulate CCN concentrations, their impact on droplet number is limited by the atmospheric dynamics expressed by the updraft velocity regime. [ABSTRACT FROM AUTHOR]

In this paper we validate the Lidar-Radiometer Inversion Code (LIRIC) retrievals of the aerosol concentration in the fine mode, using the airborne aerosol chemical composition dataset obtained over the Greater Athens Area (GAA) in Greece, during the ACEMED campaign. The study focuses on the 2nd of September 2011, when a long-range transported smoke layer was observed in the free troposphere over Greece, in the height range from 2 to 3 km. CIMEL sun-photometric measurements revealed high AOD (~ 0.4 at 532 nm) and Ångström exponent values (~ 1.7 at 440/870 nm), in agreement with coincident ground-based lidar observations. Airborne chemical composition measurements performed over the GAA, revealed increased CO volume concentration (~ 110 ppbv), with 57% sulphate dominance in the PM 1 fraction. For this case, we compare LIRIC retrievals of the aerosol concentration in the fine mode with the airborne Aerosol Mass Spectrometer (AMS) and Passive Cavity Aerosol Spectrometer Probe (PCASP) measurements. Our analysis shows that the remote sensing retrievals are in a good agreement with the measured airborne in-situ data from 2 to 4 km. The discrepancies observed between LIRIC and airborne measurements at the lower troposphere (below 2 km), could be explained by the spatial and temporal variability of the aerosol load within the area where the airborne data were averaged along with the different time windows of the retrievals. [ABSTRACT FROM AUTHOR]

Air quality forecast systems need reliable and accurate representations of the planetary boundary layer (PBL) to perform well. An important question is how accurately numerical weather prediction models can reproduce conditions in diverse synoptic flow types. Here, observations from the summer 2014 HygrA-CD (Hygroscopic Aerosols to Cloud Droplets) experimental campaign are used to validate simulations from the Weather Research and Forecasting (WRF) model over the complex, urban terrain of the Greater Athens Area. Three typical atmospheric flow types were identified during the 39-day campaign based on 2-day backward trajectories: Continental, Etesians, and Saharan. It is shown that the numerical model simulations differ dramatically depending on the PBL scheme, atmospheric dynamics, and meteorological parameter (e.g., 2-m air temperature). Eight PBL schemes from WRF version 3.4 are tested with daily simulations on an inner domain at 1-km grid spacing. Near-surface observations of 2-m air temperature and relative humidity and 10-m wind speed are collected from multiple meteorological stations. Estimates of the PBL height come from measurements using a multiwavelength Raman lidar, with an adaptive extended Kalman filter technique. Vertical profiles of atmospheric variables are obtained from radiosonde launches, along with PBL heights calculated using bulk Richardson number. Daytime maximum PBL heights ranged from 2.57 km during Etesian flows, to as low as 0.37 km during Saharan flows. The largest differences between model and observations are found with simulated PBL height during Saharan synoptic flows. During the daytime, campaign-averaged near-surface variables show WRF tended to have a cool, moist bias with higher simulated wind speeds than the observations, especially near the coast. It is determined that non-local PBL schemes give the most agreeable solutions when compared with observations. [ABSTRACT FROM AUTHOR]

In this work we extract the microphysical properties of aerosols for a collection of measurement cases with low volume depolarization ratio originating from fire sources captured by the Raman lidar located at the National Institute of Optoelectronics (INOE) in Bucharest. Our algorithm was tested not only for pure smoke but also for mixed smoke and urban aerosols of variable age and growth. Applying a sensitivity analysis on initial parameter settings of our retrieval code was proved vital for producing semi-automatized retrievals with a hybrid regularization method developed at the Institute of Mathematics of Potsdam University. A direct quantitative comparison of the retrieved microphysical properties with measurements from a Compact Time of Flight Aerosol Mass Spectrometer (CToF-AMS) is used to validate our algorithm. Microphysical retrievals performed with sun photometer data are also used to explore our results. Focusing on the fine mode we observed remarkable similarities between the retrieved size distribution and the one measured by the AMS. More complicated atmospheric structures and the factor of absorption appear to depend more on particle radius being subject to variation. A good correlation was found between the aerosol effective radius and particle age, using the ratio of lidar ratios (LR: aerosol extinction to backscatter ratios) as an indicator for the latter. Finally, the dependence on relative humidity of aerosol effective radii measured on the ground and within the layers aloft show similar patterns. [ABSTRACT FROM AUTHOR]

We report on a long-lasting (10 days) Saharan dust event affecting large sections of South-Eastern Europe by using a synergy of lidar, satellite, in-situ observations and model simulations over Athens, Greece. The dust measurements (11–20 May 2020), performed during the confinement period due to the COVID-19 pandemic, revealed interesting features of the aerosol dust properties in the absence of important air pollution sources over the European continent. During the event, moderate aerosol optical depth (AOD) values (0.3–0.4) were observed inside the dust layer by the ground-based lidar measurements (at 532 nm). Vertical profiles of the lidar ratio and the particle linear depolarization ratio (at 355 nm) showed mean layer values of the order of 47 ± 9 sr and 28 ± 5%, respectively, revealing the coarse non-spherical mode of the probed plume. The values reported here are very close to pure dust measurements performed during dedicated campaigns in the African continent. By utilizing Libradtran simulations for two scenarios (one for typical midlatitude atmospheric conditions and one having reduced atmospheric pollutants due to COVID-19 restrictions, both affected by a free tropospheric dust layer), we revealed negligible differences in terms of radiative effect, of the order of +2.6% (SWBOA, cooling behavior) and +1.9% (LWBOA, heating behavior). Moreover, the net heating rate (HR) at the bottom of the atmosphere (BOA) was equal to +0.156 K/d and equal to +2.543 K/d within 1–6 km due to the presence of the dust layer at that height. On the contrary, the reduction in atmospheric pollutants could lead to a negative HR (−0.036 K/d) at the bottom of the atmosphere (BOA) if dust aerosols were absent, while typical atmospheric conditions are estimated to have an almost zero net HR value (+0.006 K/d). The NMMB-BSC forecast model provided the dust mass concentration over Athens, while the air mass advection from the African to the European continent was simulated by the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model. [ABSTRACT FROM AUTHOR]

The irregular shape of mineral dust provides a strong signature on active and passive polarimetric remote sensing observations. Nowadays, advanced lidar systems operating in the framework of ACTRIS are capable of providing quality assured, calibrated multi-wavelength linear particle depolarization ratio measurements, while new developments will provide us elliptical polarization recordings in the near future. Passive polarimeters are already part of ACTRIS and their integration in operational retrieval algorithms is expected in the near future. This wealth of new information combined with updated scattering databases and sophisticated inversion schemes provide the means towards an improved characterization of desert dust in the future. We present here some examples from the ACTRIS journey on dust research during the last decade, aiming to demonstrate the progress on issues such as: (a) the discrimination of desert dust in external mixtures, (b) the estimation of the fine and coarse particle modes, (c) the synergy of passive and active remote sensing for the derivation of dust profiles, (d) the provision of dust-related CCN and IN particle concentrations for aerosol-cloud interaction studies, (e) the development of new scattering databases based on realistic particle shapes, (e) the application of these techniques on space lidar datasets for the provision of climatological datasets. Future plans within ACTRIS for the evaluation and advancement of the methodologies and retrievals are also discussed. [ABSTRACT FROM AUTHOR]

We analyze ten years (2008–2017) of ground-based observations of the Aerosol Optical Depth (AOD) in the atmosphere of Kuwait City, in Middle East. The measurements were conducted with a CIMEL sun-sky photometer, at various wavelengths. The daily average AOD at 500 nm (AOD500) is 0.45, while the mean Ångström coefficient (AE), calculated from the pair of wavelengths 440 and 870 nm, is 0.61. The observed high AOD500 values (0.75–2.91), are due to regional sand and dust storm events, which are affecting Kuwait with a mean annual frequency of almost 20 days/year. The long-term record analysis of AOD500 and AE, shows a downward and upward tendency respectively, something which could be attributed to the continuous expansion and industrialization of the main city of Kuwait, in combination with the simultaneous increase of soil moisture over the area. By utilizing back trajectories of air masses for up to 4 days, we assessed the influence of various regions to the aerosol load over Kuwait. The high aerosol loads during spring, are attributed to the dominance of coarse particles from Saudi Arabia (AOD500 0.56–0.74), a source area that contributes the 56% to the mean annual AOD500. Other dust sources affecting significantly Kuwait originated from the regions of Iraq and Iran with contribution of 21%. [ABSTRACT FROM AUTHOR]