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A comprehensive characterisation of atmospheric aerosols in the subtropical eastern North Atlantic has been carried out using long-term ground-based Aerosol Robotic NETwork (AERONET) photometric observations over the period 2005–2020 from a unique network made up of four stations strategically located from sea level to 3555 m on the island of Tenerife. This site can be considered a sentinel for the passage of airmasses going to Europe from Africa, and therefore the aerosol characterisation performed here adds important information for analysing their evolution during their path toward Northern Europe. Two of these stations (Santa Cruz de Tenerife – SCO – at sea level and La Laguna – LLO – at 580 m a.s.l.) are located within the marine atmospheric boundary layer (MABL), and the other two (Izaña – IZO – at 2373 m a.s.l. and Teide Peak – TPO – at 3555 m a.s.l.) are high mountain stations within the free troposphere (FT). Monthly climatology of the aerosol optical depth (AOD), Ångström exponent (AE), aerosol concentration, size distribution and aerosol optical properties has been obtained for the MABL and FT. Measurements that are quite consistent across the four sites have been used to categorise the main atmospheric scenarios, and these measurements confirm an alternation between predominant background conditions and predominant dust-loaded Saharan air mass conditions caused by seasonal dust transport over the subtropical North Atlantic. Background conditions prevail in the MABL and FT for most of the year, while dust-laden conditions dominate in July and August. The MABL under background conditions appears as a well-mixed layer with a low aerosol concentration (the volume concentration, VolCon, ranges from 0.02 ± 0.01 to 0.04 ± 0.02 µm3 µm−2), a predominance of coarse-mode marine aerosols (the effective radius, Reff, changes from 1.60 ± 0.19 to 1.91 ± 0.34 µm), and a volume contribution of the fine-mode fraction Vf/Vt . The clean FT is characterised by remarkably low aerosol loading and a predominant impact of fine-mode aerosols throughout the year (Vf/Vt has a maximum value of 0.93 ± 0.13), with an average Reff of 0.16 ± 0.02 µm. However, under dust-laden conditions and mainly in summer, we observe a predominance of coarse-mode aerosols with maximum VolCon values of 0.26 ± 0.23 µm3 µm−2 for the MABL and 0.16 ± 0.12 (0.06 ± 0.05) µm3 µm−2 for IZO (TPO), and a similar and quite consistent fine-mode fraction of 0.12 ± 0.03 in the vertical within the MABL and FT. Similarities in micro-physical and optical intensive aerosol properties confirm that the Saharan Air Layer (SAL) is a well-mixed layer in terms of the particulate composition. An estimation of the difference in the aerosol loading in the 1 km layer between IZO and TPO (in terms of VolCon and AOD) is performed in this study, and this shows that aerosol loading at IZO is double that at TPO, but they have similar fine-mode fractions, effective radii and intensive optical properties. The long-term trend analysis at SCO shows a significant negative trend in the fine-mode AOD between 2005 and 2020 (−1.8 ± 0.5) × 10−5 yr−1, which might be linked to the large reduction in oil-refining SO2 emissions from the SCO refinery in 2012.

Two layers of Saharan dust observed over Leipzig, Germany, in February and March 2021 were used to provide the first-ever lidar measurements of the dust lidar ratio (extinction-to-backscatter ratio) and linear depolarization ratio at all three classical lidar wavelengths (355, 532 and 1064 nm). The pure-dust conditions during the first event exhibit lidar ratios of 47 ± 8, 50 ± 5 and 69 ± 14 sr and particle linear depolarization ratios of 0.242 ± 0.024, 0.299 ± 0.018 and 0.206 ± 0.010 at wavelengths of 355, 532 and 1064 nm, respectively. The second, slightly polluted-dust case shows a similar spectral behavior of the lidar and depolarization ratio with values of the lidar ratio of 49 ± 4, 46 ± 5 and 57 ± 9 sr and the depolarization ratio of 0.174 ± 0.041, 0.298 ± 0.016 and 0.242 ± 0.007 at 355, 532 and 1064 nm, respectively. The results were compared with Aerosol Robotic Network (AERONET) version 3 (v3) inversion solutions and the Generalized Retrieval of Aerosol and Surface Properties (GRASP) at six and seven wavelengths. Both retrieval schemes make use of a spheroid shape model for mineral dust. The spectral slope of the lidar ratio from 532 to 1064 nm could be well reproduced by the AERONET and GRASP retrieval schemes. Higher lidar ratios in the UV were retrieved by AERONET and GRASP. The enhancement was probably caused by the influence of fine-mode pollution particles in the boundary layer which are included in the columnar photometer measurements. Significant differences between the measured and retrieved wavelength dependence of the particle linear depolarization ratio were found. The potential sources for these uncertainties are discussed.

This study presents a synergistic approach to the study of the aerosol optical and microphysical properties measured in La Palma, Spain, during the 2021 eruption of the Cumbre Vieja volcano (from 19 September to 13 December 2021). This study aims to characterize the different phases of the volcanic eruption using the spatio-temporal evolution of the event together with the mass concentration quantification of four different atmospheric layers. The impact of the plume’s pathway that reached the South of France is analyzed. Here, passive and active remote sensors were used, namely CL51 and CL61 ceilometers and AERONET sunphotometers. The attenuated backscattering ranged from 0.8 to 9.1 × 10−6 (msr)−1 and the volume depolarization ratio measured nearby the volcano was up to 0.3. The ash plume remained within the first 4 km agl, with intense episodes that reached mean aerosol optical depth values of up to 0.4. Thirteen study cases were selected where coarse mode was dominant over fine mode. For the data selection, the fine and coarse lidar ratios found were 3.9 ± 0.8 and 21.0 ± 3.8 sr in the north and 6.9 ± 1.8 and 30.1 ± 10.3 sr in the south. The ash mass concentration reached moderate levels with maximum values of up to 313.7 μgm−3.

The effects of cumulus clouds (Cu) and the combination of stratocumulus-cumulus clouds (Sc-Cu) on the solar radiation at the earth’s surface were evaluated at Camaguey (Cuba) for a 6-year period (from June 2010 to May 2016). Two methods to calculate the cloud radiative effect (CRE) were employed. The first method (CREm) uses solar irradiances in cloudy conditions from actinometric observations, where cloud information was also reported by visual observation. In the second method (CRE0) surface solar irradiances were estimated for both cloudy and clear sky conditions using a 1-D radiative transfer model, and cloud optical depth (COD) retrieved from an AERONET sun-photometer as the main input.A temporal correspondence criterion between COD retrievals and actinometric observations was performed in order to classify COD of each cloud type. After the application of this criterion, the COD belonging to the optically thin clouds was removed. Finally, 255 and 732 COD observations for Cu and Sc-Cu respectively, were found.Results show statistically significant difference at the 95% confidence level between CRE calculated for Sc-Cu and Cu, using the both methods. Mean values of CREm and CRE0 for Cu (Sc-Cu) were −442 W/m2 (−390 W/m2) and −460 W/m2 (−417 W/m2), respectively. CRE0 shows a linear relation with ln(COD), with stronger correlation at lower solar zenith angle. The shortwave cloud effect efficiency (CEE) for the two cloud types sharply decreases with the increase of the COD up to the value of 20. For larger COD, the CEE is less sensitive to the increase of COD.

All-sky cameras are frequently used to detect cloud cover; however, this work explores the use of these instruments for the more complex purpose of extracting relative sky radiances. An all-sky camera (SONA202-NF model) with three colour filters narrower than usual for this kind of cameras is configured to capture raw images at seven exposure times. A detailed camera characterization of the black level, readout noise, hot pixels and linear response is carried out. A methodology is proposed to obtain a linear high dynamic range (HDR) image and its uncertainty, which represents the relative sky radiance (in arbitrary units) maps at three effective wavelengths. The relative sky radiances are extracted from these maps and normalized by dividing every radiance of one channel by the sum of all radiances at this channel. Then, the normalized radiances are compared with the sky radiance measured at different sky points by a sun and sky photometer belonging to the Aerosol Robotic Network (AERONET). The camera radiances correlate with photometer ones except for scattering angles below 10∘, which is probably due to some light reflections on the fisheye lens and camera dome. Camera and photometer wavelengths are not coincident; hence, camera radiances are also compared with sky radiances simulated by a radiative transfer model at the same camera effective wavelengths. This comparison reveals an uncertainty on the normalized camera radiances of about 3.3 %, 4.3 % and 5.3 % for 467, 536 and 605 nm, respectively, if specific quality criteria are applied.

A comprehensive characterization of atmospheric aerosols in the Subtropical Eastern North Atlantic has been carried out using long-term ground-based Aerosol Robotic NETwork (AERONET) photometric observations from a unique network made up of four stations strategically located from the sea level to 3555 m height on the island of Tenerife over the period 2005–2020. This site is can be considered a sentinel of the passage of airmass going to Europe from Africa and therefore the aerosol characterization performed here adds important information to analyse their evolution during the path toward Northern Europe. Two of these stations (Santa Cruz de Tenerife –SCO- at sea level and La Laguna –LLO- at 580 m asl) are located within the Marine Boundary Layer 5 (MBL) and the other two (Izana –IZO- at 2373 m asl and Teide Peak –TPO- at 3555 m asl) are high mountain stations within the Free Troposphere (FT). Monthly climatology of Aerosol Optical Depth (AOD), Angstrom Exponent (AE), aerosol concentration, size distribution, and aerosol optical properties has been obtained for the MBL and FT. Quite consistent measurements at the four sites have been used to categorise the main atmospheric scenarios confirming the predominance of the alternating background to dust-loaded Saharan air mass conditions seasonally affecting the sites as a result of the seasonal dust transport over the Subtropical North Atlantic. Background conditions prevail in the MBL and FT most of the year while dust-laden conditions dominate in July and August. The MBL under background conditions appears as a well-mixed layer with low aerosol concentration (volume concentration, VolCon, ranging from 0.02±0.01 to 0.04±0.02 μm3 · μm−2) with a predominance of coarse mode marine aerosols (effective radius, Re ff, changing from 1.60±0.19 to 1.91±0.34 μm) and fine mode fraction < 0.35. The clean FT has been characterised by remarkably low aerosol loading and a predominant impact of fine mode aerosols throughout the year (V f / V t with a maximum value of 0.93±0.13) with an average Re ff of 0.16±0.02 μm. However, under dust-laden conditions, we observe the predominance of coarse mode aerosols, mainly in summer, with maximum VolCon values of 0.26±0.23 μm3 · μm−2 for MBL and 0.16±0.12 (0.06±0.05) μm3 · μm−2 for IZO (TPO) and a similar and quite consistent fine mode fraction of 0.120.03 in the vertical within MBL and FT. Similarities in micro-physical and optical intensive aerosol properties confirm the Saharan Air Layer (SAL) as a well-mixed layer in terms of the particulate composition. An estimation of the difference in the aerosol loading in the 1-km layer between IZO and TPO (in terms of VolCon and AOD) is performed in this study, showing that aerosol loading at IZO is double that of TPO but with similar fine mode fraction, effective radius and optical intensive properties. The long-term trend analysis at SCO shows a negative significant trend in the fine AOD mode between 2005 and 2020 (-1.8±0.5) ·10−5 yr−1, which might be linked to the large reduction of oil refining SO2 emissions at SCO refinery in 2012.

This paper presents the software application ORION (All-sky camera geOmetry calibRation from star positIONs). This software has been developed with the aim of providing geometrical calibration to all-sky cameras, i.e. assess which sky coordinates (zenith and azimuth angles) correspond to each camera pixel. It is useful to locate bodies over the celestial vault, like stars and planets, in the camera images. The user needs to feed ORION with a set of cloud-free sky images captured at night-time for obtaining the calibration matrices. ORION searches the position of various stars in the sky images. This search can be automatic or manual. The sky coordinates of the stars and the corresponding pixel positions in the camera images are used together to determine the calibration matrices. The calibration is based on three parameters: the pixel position of the sky zenith in the image; the shift angle of the azimuth viewed by the camera with respect to the real North; and the relationship between the sky zenith angle and the pixel radial distance regards to the sky zenith in the image. In addition, ORION includes other features to facilitate its use, such as the check of the accuracy of the calibration. An example of ORION application is shown, obtaining the calibration matrices for a set of images and studying the accuracy of the calibration to predict a star position. Accuracy is about 9.0 arcmin for the analyzed example using a camera with average resolution of 5.4 arcmin/pixel (about 1.7 pixels).

This paper explores the potential of all-sky cameras to retrieve aerosol properties with GRASP code (Generalized Retrieval of Atmosphere and Surface Properties). To this end, normalized sky radiances (NSR) extracted from an all-sky camera at three effective wavelengths (467, 536 and 605 nm) are used in this study. NSR observations are a set of relative (uncalibrated) sky radiances in arbitrary units. NSR observations have been simulated for different aerosol loads and types with the forward radiative transfer module of GRASP, indicating that NSR observations contain information about the aerosol type as well as about the aerosol optical depth (AOD), at least for low and moderate aerosol loads. An additional sensitivity study with synthetic data has been carried out to quantify the theoretical accuracy and precision on the aerosol properties (AOD, size distribution parameters, etc.) retrieved by GRASP using NSR observations as input. As result, the theoretical accuracy on AOD is within ±0.02 for AOD values lower or equal than 0.4; while the theoretical precision goes from 0.01 to 0.05 when AOD at 467 nm varies from 0.1 to 0.5. NSR measurements recorded at Valladolid (Spain) with an all-sky camera for more than two years have been inverted with GRASP. The retrieved aerosol properties are compared with independent values provided by co-located AERONET (AErosol RObotic NETwork) measurements. AOD from both data sets correlate with determination coefficient (r2) values about 0.87. Finally, the novel multi-pixel approach of GRASP is applied to daily camera radiances together, by constraining the temporal variation in certain aerosol properties. This temporal linkage (multi-pixel approach) provides promising results, reducing the highly temporal variation in some aerosol properties retrieved with the standard (one by one or single-pixel) approach. This work implies an advance in the use of all-sky cameras for the retrieval of aerosol properties.

The rapidly growing field of cancer immunotherapy has led to the development of new treatments such as immune checkpoint inhibitors. These agents are monoclonal antibodies that enable tumor-reactive T cells to overcome regulatory mechanisms and produce effective antitumor responses. The use of immune checkpoint inhibitors is expected to progressively increase because they have shown promising therapeutic outcomes in multiple types of cancer and clinicians should be aware of their possible side-effects. We report a case of a man diagnosed with a non-microcytic lung carcinoma who started treatment with a combination of immune checkpoint inhibitors (Nivolumab and Ipilimumab). He subsequently developed binocular diplopia, fatigue, mild dyspnea and upper back pain resembling a myasthenia gravis presentation. Finally, a diagnosis of immune checkpoint inhibitor-related myositis and myocarditis was made. The detection of GFAP antibodies in CSF has unclear clinical and pathogenic significance and they may rather represent an epiphenomenon of the immune inflammation process.

The objective is to derive methane (CH4) emissions of the metropolitan city Madrid Spain from the CH4 enhancements seen by the space-borne and the ground-based instruments. This study applies satellite-based measurements from the TROPOspheric Monitoring Instrument (TROPOMI) and the Infrared Atmospheric Sounding Interferometer (IASI) together with measurements from the ground-based COllaborative Carbon Column Observing Network (COCCON) instruments. In 2018, a two-week field campaign for measuring the atmospheric concentrations of greenhouse gases was performed in Madrid in the framework of Monitoring greenhousE Gas EmIssions of Madrid city (MEGEI-MAD) project. Five COCCON instruments were deployed at different locations around the Madrid city center enabling the observation of total column averaged CH4 mixing ratios (XCH4). Using available wind data, the differences between CH4 columns observed at these locations allow to estimate the emissions emerging from the surrounded area. In addition, based on the dominating wind direction in the Madrid region, we calculate the difference of the satellite data maps for two opposite wind regimes (northeast – southwest, NE – SW). In the following, we refer to the resultant signal as the wind-assigned anomaly. We use TROPOMI tropospheric nitrogen dioxide (NO2) observations as a test to verify our method of wind-assigned anomaly and its implementation, taking advantage of the much better detectability of the plume due to the short lifetime and low background concentrations of NO2. Pronounced bipolar plumes are found along NE and SW wind direction, which implies that our method of wind-assigned anomaly is working as expected. The wind-assigned TROPOMI XCH4 anomaly shows much weaker symmetric plumes than NO2 due to the long lifetime of CH4 and in consequence a high accumulated background of CH4 in the atmosphere. The wind-assigned plume method is also applied to the tropospheric and upper tropospheric/stratospheric column averaged CH4 mixing ratio products (in the following referred to as TXCH4 and UTSXCH4) derived from a-posteriori merged Infrared Atmospheric Sounding Interferometer (IASI) profile and TROPOMI total column data. Based on the NE and SW wind fields, we developed a simple plume model locating the source at three waste disposal sites east of Madrid for CH4. As CH4 emission strength we estimate 7.4 × 1025 ± 6.4 × 1024 molec s−1 from the TROPOMI XCH4 data and 7.1 × 1025 ± 1.0 × 1025 molec s−1 from the TROPOMI&IASI merged TXCH4 data. The COCCON observations indicate a weaker CH4 emission strength of around 3.7 × 1025 molec s−1 from local source (near to the Valdemingómez waste plant) in accordance with observations in a single day and. All emission rates estimated from the different observations are significantly larger than the emission rates provided via the official Spanish Register of Emissions and Pollutant Sources.

Background Erenumab was approved in Europe for migraine prevention in patients with ≥4 monthly migraine days (MMD). In Spain, Novartis started a personalized managed access program which allowed free access to erenumab before official reimbursement. The Headache Study Group of the Spanish Neurological Society started a registry to monitor real-world safety and efficacy, and all Spanish headache experts were invited to participate. Methods Patients fulfilled ICHD3 criteria for migraine and had ≥ 4MMD. Sociodemographic and clinical data were registered as well as MMD, headache frequency (MHD), prior and concomitant preventive treatment, medication overuse headache (MOH), migraine evolution, adverse events, and PROs: HIT6, MIDAS, and PGIC. A >50% reduction of MMD after 3 months was considered as response. Results We included 210 patients (female 86.7%, mean age 46.4 years old) from 22 hospitals from February 2019 – to – June 2020. Most patients (89.5%) suffered from chronic migraine with a mean evolution of 8.6 years. MOH was present in 70% of patients, and 17.1% had migraine with aura. Average of prior preventive treatment failure was >7 (BoNT/A had been used by 95.2%). Most patients (67,6%) started with erenumab 70mg. 61% of patients were also taking oral preventive drugs or getting simultaneous BoNT/A (27.6%). Responder rate was 37.1% and the mean reduction of MMD was -6.28 and MHD: -8.6. Regarding PROs: MIDAS: -35 p., HIT6: -11.6 p., PIGC: 4.7 p. Predictors of good response were: HIT6 score ( p =0.01), prior preventive treatment failures ( p =0.026), absence of MOH ( p =0.039), and simultaneous BoNT/A treatment ( p

Atmospheric aerosols are an important forcing agent in the estimation of radiative budget, being the Arctic an area of special weakness. The Group of Atmospheric Optics, University of Valladolid and the Alfred Wegener Institute for Polar and Marine Research, installed in 2017 a CE-318T Sun-sky-Moon photometer (Cimel Electronique S.A.S) in the Arctic station Ny-Ålesund (79ºN, 12ºE). This study presents an inventory of all high-turbidity aerosol episodes recorded in the period 2017-2020 (data of level 1.5-validated from AERONET). This inventory is based on the separate analysis of coarse and fine mode aerosol optical depth. Aerosol episodes are attributed to coarse, fine or mixture of aerosols. Complementary information provided by HYSPLIT air mass back trajectories, MODIS images, forecast aerosol models, CALIOP/CALIPSO satellite data, and other collocated instruments on the station are also used. Special focus is given to long-range transport of aerosols from big forest fires in Canada, United States and Russia.

Long range transported aerosol from biomass burning affects polar regions, especially the Arctic. The frequency and intensity of bushfires in the context of a warming climate has been pointed out in the last report of the Intergovernmental Panel on Climate Change. In high latitudes, these events impact large areas through long-range transport of the smoke particles in the troposphere or even the stratosphere. The lifetime and radiative impact are related with the height of the plumes and the processes that modify particle size and absorptive properties during the transport. Several recent publications have shown the impact of the Australian smoke in the southern hemisphere, including Antarctica, in January-March 2020. The tools that were used to monitor that extraordinary event can be used in the Arctic to investigate similar effects in the frequent biomass burning events that generate smoke plumes in boreal regions. In this work, we present the results derived from ground-based instrumentation as well as satellite and model data. The change of the smoke properties after several days of transport is also provided, namely an increase in the fine mode particle size and the single scattering albedo, as well as a decrease in the coarse mode particle concentration. These features are relevant for radiative forcing calculations and therefore the impact of long range transported smoke in the radiative balance over polar regions.

Absolute calibration of Earth observation sensors is key to ensuring long term stability and interoperability, essential for long term global climate records and forecasts. The Moon provides a photometrically stable calibration source, within the range of the Earth radiometric levels, and is free from atmospheric interference. However, to use this ideal calibration source, one must model the variation of its disk integrated irradiance resulting from changes in Sun-Earth-Moon geometries.LIME, the Lunar Irradiance Model of the European Space Agency, is a new lunar irradiance model developed from ground-based observations acquired using a lunar photometer operating from the Izaña Atmospheric Observatory and Teide Peak, Tenerife. Approximately 300 lunar observations acquired between March 2018 and October 2020 currently contribute to the model, which builds on the widely-used ROLO (Robotic Lunar Observatory) model.This presentation will outline the strategy used to derive LIME. First, the instrument was calibrated traceably to SI and characterised to determine its thermal sensitivity and its linearity over the wide dynamic range required. Second, the instrument was installed at the observatory, and nightly observations over a two-hour time window were extrapolated to provide top-of-atmosphere lunar irradiance using the Langley plot method. Third, these observations were combined to derive the model. Each of these steps includes a metrologically rigorous uncertainty analysis.Comparisons to several EO sensors will be presented including Proba-V, Pleiades and Sentinel 3A and 3B, as well as a comparison to GIRO, the GSICS implementation of the ROLO model. Initial results indicate LIME predicts 3% - 5% higher disk integrated lunar irradiance than the GIRO/ROLO model for the visible and near-infrared channels. The model has an expanded (k = 2) absolute radiometric uncertainty of ~2%, and it is expected that planned observations until at least 2024 will further constrain the model in subsequent updates.

Producción Científica, Australian smoke from the extraordinary biomass burning in December 2019 was observed over Marambio, Antarctica from the 7th to the 10th January, 2020. The smoke plume was transported thousands of kilometers over the Pacific Ocean, and reached the Antarctic Peninsula at a hight of 13 km, as determined by satellite lidar observations. The proposed origin and trajectory of the aerosol are supported by back-trajectory model analyses. Ground-based Sun–Sky–Moon photometer belonging to the Aerosol Robotic Network (AERONET) measured aerosol optical depth (500 nm wavelength) above 0.3, which is unprecedented for the site. Inversion of sky radiances provide the optical and microphysical properties of the smoke over Marambio. The AERONET data near the fire origin in Tumbarumba, Australia, was used to investigate the changes in the measured aerosol properties after transport and ageing. The analysis shows an increase in the fine mode particle radius and a reduction in absorption (increase in the single scattering albedo). The available long-term AOD data series at Marambio suggests that smoke particles could have remained over Antarctica for several weeks after the analyzed event., Ministerio de Ciencia, Innovación y Universidades (Proyecto RTI2018-097864-B-I00), Academy of Finland (project number 264390), Finnish Academy of Sciences Excellence (project number 307331), European Union’s Horizon 2020 (grant agreement number 654109)

The emergence of Moon photometers is allowing measurements of lunar irradiance over the world and increasing the potential to derive aerosol optical depth (AOD) at night-time, that is very relevant in polar areas. Actually, new photometers implement the latest technological advances that permit lunar irradiance measurements together with classical Sun photometry measurements. However, a proper use of these instruments for AOD retrieval requires accurate time-dependent knowledge of the extraterrestrial lunar irradiance over time, due to its fast change throughout the Moon's cycle. This paper uses the RIMO model (an implementation of the ROLO model) to estimate the AOD at night-time assuming that the calibration of the solar channels can be transferred to the Moon by a vicarious method. However, the obtained AOD values using a Cimel CE318-T Sun/sky/Moon photometer for 98 pristine nights with low and stable AOD at the Izaña Observatory (Tenerife, Spain) are not in agreement with the expected (low and stable) AOD values, estimated by linear interpolations from daytime values obtained during the previous evening and the following morning. Actually, AOD calculated using RIMO shows negative values and with a marked cycle dependent on the optical airmass. The differences between the AOD obtained using RIMO and the expected values are assumed to be associated with inaccuracies in the RIMO model, and these differences are used to calculate the RIMO correction factor (RCF). The RCF is a proposed correction factor that, multiplied by RIMO value, gives an effective extraterrestrial lunar irradiance that provides the expected AOD values. The RCF varies with the Moon phase angle (MPA) and with wavelength, ranging from 1.01 to 1.14, which reveals an overall underestimation of RIMO to the lunar irradiance. These obtained RCF values are modeled for each photometer wavelength to a second order polynomial as function of MPA. The AOD derived by this proposed method is compared with the independent AOD measurements obtained by a star photometer at Granada (Spain) for two years. The mean of the Moon-star AOD differences are between −0.015 and −0.005 and the standard deviation between 0.03 and 0.04 (which is reduced to about 0.01 if one month of data affected by instrumental issues is not included in the analysis), for 440, 500, 675 ad 870 nm; however, for 380 nm, the mean and standard deviation of these differences are higher. The Moon-star AOD differences are also analyzed as a function of MPA, showing no significant dependence.

The University of Valladolid (UVa, Spain) manages since 2006 a calibration center of the AErosol RObotic NETwork (AERONET). The CÆLIS software tool, developed by UVa, was created to manage the data generated by the AERONET photometers, for calibration, quality control and data processing purposes. This paper exploits the potential of this tool in order to obtain products like the aerosol optical depth (AOD) and Angstrom exponent (AE), which are of high interest for atmospheric and climate studies, as well as to enhance the quality control of the instruments and data managed by CÆLIS. The AOD and cloud screening algorithms implemented in CÆLIS, both based on AERONET version 3, are described in detail. The obtained products are compared with the AERONET database. In general, the differences in daytime AOD between CÆLIS and AERONET are far below the expected uncertainty of the instrument, ranging the mean differences between −1.3×10−4 at 870 nm and 6.2×10−4 at 380 nm. The standard deviations of the differences range from 2.8×10−4 at 675 nm to 8.1×10−4 at 340 nm. The AOD and AE at night-time calculated by CÆLIS from Moon observations are also presented, showing good continuity between day and night-time for different locations, aerosol loads and moon phase angles. Regarding cloud screening, around 99.9 % of the observations classified as cloud-free by CÆLIS are also assumed cloud-free by AERONET; this percentage is similar for the cases considered as cloud-contaminated by both databases. The obtained results point out the capability of CÆLIS as processing system. The AOD algorithm provides the opportunity to use this tool with other instrument types and to retrieve other aerosol products in the future.

In this chapter remote sensing techniques as applied to studies of Arctic aerosol are surveyed. They include the analysis of ground and shipborne observations of atmospheric aerosol using sunphotometers and also airborne/satellite observations using optical instrumentation (lidars, imagers, radiometers).

This work presents an evaluation of a surprising and unusual high turbidity summer period in 2013 recorded in the north-central Iberian Peninsula (IP). The study is made up of three main pollution episodes characterized by very high aerosol optical depth (AOD) values with the presence of fine aerosol particles: the strongest long-range transport Canadian Biomass Burning (BB) event recorded, one of the longest-lasting European Anthropogenic (A) episodes and an extremely strong regional BB. The Canadian BB episode was unusually strong with maximum values of AOD(440 nm) ∼ 0.8, giving rise to the highest value recorded by photometer data in the IP with a clearly established Canadian origin. The anthropogenic pollution episode originated in Europe is mainly a consequence of the strong impact of Canadian BB events over north-central Europe. As regards the local episode, a forest fire in the nature reserve near the Duero River (north-central IP) impacted on the population over 200 km away from its source. These three episodes exhibited fingerprints in different aerosol columnar properties retrieved by sun-photometers of the AErosol RObotic NETwork (AERONET) as well as in particle mass surface concentrations, PMx, measured by the European Monitoring and Evaluation Programme (EMEP). Main statistics, time series and scatterplots relate aerosol loads (aerosol optical depth, AOD and particulate matter, PM) with aerosol size quantities (Angstrom Exponent and PM ratio). More detailed microphysical/optical properties retrieved by AERONET inversion products are analysed in depth to describe these events: contribution of fine and coarse particles to AOD and its ratio (the fine mode fraction), volume particle size distribution, fine volume fraction, effective radius, sphericity fraction, single scattering albedo and absorption optical depth. Due to its relevance in climate studies, the aerosol radiative effect has been quantified for the top and bottom of the atmosphere, obtaining mean daily values for this extraordinary summer period of −14.5 and −47.5 Wm−2, respectively.

North Africa is the world’s largest source of dust, a large part of which is transported across the Atlantic to the Caribbean and beyond where it can impact radiation and clouds. Many aspects of this transport and its climate effects remain speculative. The Saharan Aerosol Long-Range Transport and Aerosol–Cloud-Interaction Experiment (SALTRACE; www.pa.op.dlr.de/saltrace) linked ground-based and airborne measurements with remote sensing and modeling techniques to address these issues in a program that took place in 2013/14. Specific objectives were to 1) characterize the chemical, microphysical, and optical properties of dust in the Caribbean, 2) quantify the impact of physical and chemical changes (“aging”) on the radiation budget and cloud microphysical processes, 3) investigate the meteorological context of transatlantic dust transport, and 4) assess the roles of removal processes during transport. SALTRACE was a German-led initiative involving scientists from Europe, Cabo Verde, the Caribbean, and the United States. The Falcon research aircraft of the Deutsches Zentrum für Luft- und Raumfahrt (DLR), equipped with a comprehensive aerosol and wind lidar payload, played a central role. Several major dust outbreaks were studied with 86 h of flight time under different conditions, making it by far the most extensive investigation on long-range transported dust ever made. This article presents an overview of SALTRACE and highlights selected results including data from transatlantic flights in coherent air masses separated by more than 4,000-km distance that enabled measurements of transport effects on dust properties. SALTRACE will improve our knowledge on the role of mineral dust in the climate system and provide data for studies on dust interactions with clouds, radiation, and health.

Aerosol extinction vertical profiles at Granada (Spain) are calculated with the GRASP (Generalized Retrieval of Aerosol and Surface Properties) code using as input Aerosol Optical Depth (AOD) and sky radiance measurements from AERONET (AEerosol RObotic NETwork) and ceilometer RCS (Range Corrected Signal) profiles, both corresponding to the Granada (Spain) station. This methodology is so called GRASPpac due to the combination of sun/sky photometer and ceilometer on GRASP. In order to evaluate the accuracy of these retrieved extinction profiles at Granada, two more nearby AERONET stations, located at different altitudes, are used. The AOD difference of the three choosen AERONET sun/sky photometers have been used to calculate the Integrated Aerosol Extinction (IAE) at different height layers. These three AERONET sun/sky photometers are used as a reference and compared against the integrated extinction at the same layers from the extinction profiles retrieved by GRASPpac. The differences between AERONET and GRASPpac retrieved IAE values indicate that GRASPpac aerosol extinction profiles are at least within the uncertainty of the sun/sky photometer measurements, but GRASPpac method overestimates the AERONET extinction at low altitudes and underestimates it at high levels. The most accurate and precise retrieved extinction correspond to the intermediate layer with a mean bias error (MBE ± standard deviation) of 0.00 ± 0.01 (0 ± 59%) for 1020 nm, and the worst integrated extinction results were obtained for the upper layers with a MBE of −0.01 ± 0.02 (28 ± 36%) for 1020 nm. In general these MBE values increases for shorter wavelengths. In order to obtain a complete characterization of this bias, the dependence of the obtained differences on the aerosol size and the solar zenith angle, among others, are analysed in detail. Finally, the behaviour of vertically-resolved aerosol extinction at Granada is evaluated using averages of the retrieved profiles from November of 2012 to December of 2017. The highest IAE values are found in Summer with mean values of 0.09 for the lower layers and 0.07 for the upper ones, both at 440 nm wavelength., Andalusia Regional Government (project P12-RNM-2409), “Consejería de Educación” of “Junta de Castilla y León” (project VA100U14), Spanish Ministry of Economy and Competitiveness under the projects, CMT2015-66742-R, CGL2016-81092-R, “Juan de la Cierva-Incorporación” program (FIJCI-2016-30007) and CGL2017-90884-REDT

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.

International audience; The authors regret that there is an error in equation 12. The right equation for κλ, as is defined in Barreto et al. (The new Sun-sky-lunar Cimel CE318-T multiband photometer - a comprehensive performance evaluation, Atmos. Meas. Tech., 9, 631-654, 10.5194/amt-9-631-2016, 2016), is the reversed form of equation 12. That is: κλ = V0,λ*G/E0,λ.

International audience; Ceilometers are widely spread instruments mainly used for cloud base height determination. However, recent models are more sensitive to aerosols; hence, nowadays there is an increasing interest in these instruments to retrieve aerosol optical and microphysical properties.The high number of them distributed around the globe compared to the robust lidar systems and the fact that ceilometers work under unattended conditions are the main reasons behind this interest. In this paper a new methodology is proposed to retrieve aerosol vertical extinction and backscatter profiles from a Vaisala ceilometer CL51. This methodology is based in two parts: first, a signal pre-processing with a suppression of the dark current and background noises, and a correction of the water vapor absorption using near-real time temperature and absolute humidity (AH) profiles from a co-located Microwave radiometer (MWR). Then an iterative Klett-based algorithm that uses AERONET (AErosol RObotic NETwork) AOD (Aerosol Optical Depth) as an input to retrieve the extinction and backscatter profiles. The error analysis of the aerosol retrievals has been performed between MWR measurements and modelled radiosondes from HYSPLIT. The absolute errors found in temperature and AH are leading to errors in the pre-processed RCS signals up to 9%, and then in particle backscatter and particle extinction coefficients up to 2:2% and 25%, respectively.; Les ceilomètres sont des instruments très répandus, principalement utilisés pour déterminer la hauteur de la base des nuages. Cependant, des modèles récents sont plus sensibles aux aérosols ; c'est pourquoi, de nos jours, on s'intéresse de plus en plus à ces instruments pour mesurer des données optiques des aérosols et leurs propriétés microphysiques. Le nombre élevé de ces derniers, répartis dans le monde entier, par rapport aux systèmes lidar robustes et le fait que les plafonds fonctionnent dans des conditions non surveillées sont les principales raisons de cet intérêt. Dans ce document, une nouvelle méthodologie est proposée pour déterminer par inversion les profils d'extinction verticale et de rétrodiffusion des aérosols à partir d'un modèle CL51 de ceilomètre de Vaisala. Cette méthodologie est basée sur deux parties : premièrement, un prétraitement du signal avec une suppression du courant d'obscurité et du fond et une correction de l'absorption de la vapeur d'eau en utilisant des profils de température et d'humidité absolue (AH) en temps quasi réel d'un radiomètre à micro-ondes (MWR) colocalisé. Ensuite, un algorithme itératif basé sur Klett qui utilise AERONET (AErosol RObotic NETwork) AOD (Aerosol Optical Depth) comme entrée est appliquée pour récupérer les profils d'extinction et de rétrodiffusion. Les erreurs absolues trouvées dans la température et l'AH entraînent des erreurs dans les signaux RCS prétraités jusqu'à 9 %, puis dans les coefficients de rétrodiffusion et d'extinction des particules jusqu'à 2,2 % et 25 %, respectivement.

A reliable identification of desert dust (DD) episodes over north-central Spain is carried out based on the AErosol RObotic NETwork (AERONET) columnar aerosol sun photometer (aerosol optical depth, AOD, and Ångström exponent, α) and European Monitoring and Evaluation Programme (EMEP) surface particulate-mass concentration (PMx, x = 10, 2.5, and 2.5–10 µm) as the main core data. The impact of DD on background aerosol conditions is detectable by means of aerosol load thresholds and complementary information provided by HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory Model) air mass back trajectories, MODIS (Moderate Resolution Imaging Spectroradiometer) images, forecast aerosol models, and synoptic maps, which have been carefully reviewed by a human observer for each day included in the DD inventory. This identification method allows the detection of low and moderate DD intrusions and also of mixtures of mineral dust with other aerosol types by means of the analysis of α. During the period studied (2003–2014), a total of 152 DD episodes composed of 418 days are identified. Overall, this means ∼ 13 episodes and ∼ 35 days per year with DD intrusion, representing 9.5 % days year−1. During the identified DD intrusions, 19 daily exceedances over 50 µg m−3 are reported at the surface. The occurrence of DD event days during the year peaks in March and June, with a marked minimum in April and lowest occurrence in winter. A large interannual variability is observed showing a statistically significant temporal decreasing trend of ∼ 3 days year−1. The DD impact on the aerosol climatology is addressed by evaluating the DD contribution in magnitude and percent (in brackets) for AOD, PM10, PM2.5, and PM2.5 − 10, obtaining mean values of 0.015 (11.5 %), 1.3 µg m−3 (11.8 %), 0.55 µg m−3 (8.5 %) and 0.79 µg m−3 (16.1 %), respectively. Annual cycles of the DD contribution for AOD and PM10 present two maxima – one in summer (0.03 and 2.4 µg m−3 for AOD in June and PM10 in August) and another in March (0.02 for AOD and 2.2 µg m−3 for PM10) – both displaying a similar evolution with exceptions in July and September. The seasonal cycle of the DD contribution to AOD does not follow the pattern of the total AOD (close to a bell shape), whereas both PM10 cycles (total and DD contribution) are more similar to each other in shape, with an exception in September. The interannual evolution of the DD contribution to AOD and PM10 has evidenced a progressive decrease. This decline in the levels of mineral dust aerosols can explain up to 30 % of the total aerosol load decrease observed in the study area during the period 2003–2014. The relationship between columnar and surface DD contribution shows a correlation coefficient of 0.81 for the interannual averages. Finally, synoptic conditions during DD events are also analysed, observing that the north African thermal low causes most of the events ( ∼ 53 %). The results presented in this study highlight the relevance of the area studied since it can be considered representative of the clean background in the western Mediterranean Basin where DD events have a high impact on aerosol load levels.