Suchergebnisse

This research was supported by the European Commission's Horizon 2020 Framework Programme (ACTRIS2 (grant agreement no. 654109)), the University of Helsinki, the Finnish Meteorological Institute, the Department of Science and Innovation of South Africa, the Academy of Finland Centre of Excellence programme (project no. 272041), the Academy of Finland project Greenhouse gas, aerosol and albedo variations in the changing Arctic (project no. 269095), the Novel Assessment of Black Carbon in the Eurasian Arctic: From Historical Concentrations and Sources to Future Climate Impacts (NABCEA, project no. 296302), the Korea Meteorological Administration Research and Development Program "Development of Monitoring and Analysis Techniques for Atmospheric Composition in Korea" (grant no. KMA2018-00522), the National Research Foundation of Korea (grant no. 2017R1D1A1B06032548), the Korea Meteorological Administration Research and Development Program (grant no. KMI2018-01111), the Taiwan Environmental Protection Administration, the China Meteorological Administration, the National Scientific Foundation of China (41675129, 41875147), the National Key R&D Program of the Ministry of Science and Technology of the People's Republic of China (grant no. 2016YFC0203305 and 2018YFC0213204), the Chinese Academy of Meteorological Sci-ences (2020KJ001), the Innovation Team for Haze-fog Observation and Forecasts of MOST and CMA, CNRS-INSU, the French Ministry for Research under the ACTRIS-FR national research infrastructure, the French Ministry of the Environment, MeteoSwiss (GAW-CH aerosol monitoring programme), the Swiss State Secretariat for Education, Research and Innovation (SERI), the Ministry of Education, Youth and Sports of CR within National Sustainability Program I (NPU I, grant no. LO1415), ERDF "ACTRISCZ RI" (grant no. CZ.02.1.01/0.0/0.0/16_013/0001315), CRISOL (CGL2017-85344-R MINECO/AEI/FEDER, UE), TIGAS-CM (Madrid Regional Government Y2018/EMT-5177), AIRTECCM (Madrid Regional Government P2018/EMT4329), REDMAAS2020 (RED2018-102594-T CIENCIA), Red de Excelencia ACTRIS-ESPANA (CGL2017-90884-REDT), the Spanish Ministry of Economy, Industry and Competitiveness, FEDER funds (project HOUSE, grant no. CGL2016-78594-R), the Generalitat de Catalunya (AGAUR 2017 SGR41 and the DGQA), the National Institute for Aerospace Technology, the Ministerio Espanol de Economia, Industria y Competitividad (MINECO), the Spanish Ministry of Economy and Competitiveness (projects no. CGL2016-81092-R, CGL2017-90884-REDT, RTI2018-097864-BI00 and PGC2018-098770-B-I00), the Andalusia Regional Government (project no. P18-RT-3820), the PANhellenic infrastructure for Atmospheric Composition and climate change (MIS 5021516), Research and Innovation Infrastructure, Competitiveness, Entrepreneurship and Innovation (grant no. NSRF 20142020), the Italian Ministry of Research and Education, the Norwegian Environment Agency, Swedish FORMAS, the Swedish Research Council (VR), the Magnus Bergvall foundation, the Marta och Erik Holmberg foundation, and the Swedish EPA. ; Aerosol particles are a complex component of the atmospheric system which influence climate directly by interacting with solar radiation, and indirectly by contributing to cloud formation. The variety of their sources, as well as the multiple transformations they may undergo during their transport (including wet and dry deposition), result in significant spatial and temporal variability of their properties. Documenting this variability is essential to provide a proper representation of aerosols and cloud condensation nuclei (CCN) in climate models. Using measurements conducted in 2016 or 2017 at 62 ground-based stations around the world, this study provides the most up-to-date picture of the spatial distribution of particle number concentration (N-tot) and number size distribution (PNSD, from 39 sites). A sensitivity study was first performed to assess the impact of data availability on N-tot's annual and seasonal statistics, as well as on the analysis of its diel cycle. Thresholds of 50% and 60% were set at the seasonal and annual scale, respectively, for the study of the corresponding statistics, and a slightly higher coverage (75 %) was required to document the diel cycle. Although some observations are common to a majority of sites, the variety of environments characterizing these stations made it possible to highlight contrasting findings, which, among other factors, seem to be significantly related to the level of anthropogenic influence. The concentrations measured at polar sites are the lowest (similar to 10(2) cm(-3)) and show a clear seasonality, which is also visible in the shape of the PNSD, while diel cycles are in general less evident, due notably to the absence of a regular day-night cycle in some seasons. In contrast, the concentrations characteristic of urban environments are the highest (similar to 10(3)-10(4) cm(-3)) and do not show pronounced seasonal variations, whereas diel cycles tend to be very regular over the year at these stations. The remaining sites, including mountain and non-urban continental and coastal stations, do not exhibit as obvious common behaviour as polar and urban sites and display, on average, intermediate N-tot (similar to 10(2)-10(3) cm(-3)). Particle concentrations measured at mountain sites, however, are generally lower compared to nearby lowland sites, and tend to exhibit somewhat more pronounced seasonal variations as a likely result of the strong impact of the atmospheric boundary layer (ABL) influence in connection with the topography of the sites. ABL dynamics also likely contribute to the diel cycle of N-tot observed at these stations. Based on available PNSD measurements, CCN-sized particles (considered here as either >50 nm or >100 nm) can represent from a few percent to almost all of N-tot, corresponding to seasonal medians on the order of similar to 10 to 1000 cm(-3), with seasonal patterns and a hierarchy of the site types broadly similar to those observed for N-tot. Overall, this work illustrates the importance of in situ measurements, in particular for the study of aerosol physical properties, and thus strongly supports the development of a broad global network of near surface observatories to increase and homogenize the spatial coverage of the measurements, and guarantee as well data availability and quality. The results of this study also provide a valuable, freely available and easy to use support for model comparison and validation, with the ultimate goal of contributing to improvement of the representation of aerosol-cloud interactions in models, and, therefore, of the evaluation of the impact of aerosol particles on climate. ; European Commission's Horizon 2020 Framework Programme (ACTRIS2) 654109 ; University of Helsinki ; Finnish Meteorological Institute ; Department of Science and Innovation of South Africa ; Academy of Finland 272041 ; Academy of Finland project Greenhouse gas, aerosol and albedo variations in the changing Arctic 269095 ; Novel Assessment of Black Carbon in the Eurasian Arctic: From Historical Concentrations and Sources to Future Climate Impacts (NABCEA) 296302 ; Korea Meteorological Administration Research and Development Program "Development of Monitoring and Analysis Techniques for Atmospheric Composition in Korea" KMA2018-00522 ; National Research Foundation of Korea 2017R1D1A1B06032548 ; Korea Meteorological Administration Research and Development Program KMI2018-01111 ; Taiwan Environmental Protection Administration ; China Meteorological Administration ; National Natural Science Foundation of China (NSFC) 41675129 41875147 ; National Key R&D Program of the Ministry of Science and Technology of the People's Republic of China 2016YFC0203305 2018YFC0213204 ; Chinese Academy of Meteorological Sciences 2020KJ001 ; Innovation Team for Haze-fog Observation and Forecast of MOST Innovation Team for Haze-fog Observation and Forecast of CMA Innovation Team for Haze-fog Observation and Forecast of CNRS-INSU ; French Ministry for Research under the ACTRIS-FR national research infrastructure ; French Ministry of the Environment, MeteoSwiss (GAW-CH aerosol monitoring programme) ; Swiss State Secretariat for Education, Research and Innovation (SERI) ; Ministry of Education, Youth and Sports of CR within National Sustainability Program I (NPU I) LO1415 ; ERDF "ACTRISCZ RI" CZ.02.1.01/0.0/0.0/16_013/0001315 ; CRISOL CGL2017-85344 ; TIGAS-CM (Madrid Regional Government) Y2018/EMT-5177 ; AIRTECCM (Madrid Regional Government) P2018/EMT4329 ; REDMAAS2020 RED2018-102594-T ; Red de Excelencia ACTRIS-ESPANA CGL2017-90884-REDT ; Spanish Ministry of Economy, Industry and Competitiveness, FEDER funds CGL2016-78594-R ; Generalitat de Catalunya ; General Electric AGAUR 2017 SGR41 ; National Institute for Aerospace Technology ; Ministerio Espanol de Economia, Industria y Competitividad (MINECO) Spanish Government CGL2017-90884-REDT CGL2016-81092-R RTI2018-097864-BI00 PGC2018-098770-B-I00 ; Andalusia Regional Government P18-RT-3820 ; PANhellenic infrastructure for Atmospheric Composition and climate change MIS 5021516 ; Research and Innovation Infrastructure, Competitiveness, Entrepreneurship and Innovation NSRF 20142020 ; Ministry of Education, Universities and Research (MIUR) ; Norwegian Environment Agency, Swedish FORMAS ; Swedish Research Council ; Magnus Bergvall foundation ; Marta och Erik Holmberg foundation ; Swedish EPA

A substantial fraction of the atmospheric aerosols originates from secondary new particle formation (NPF), where atmospheric vapours are transformed into particles that subsequently grow to larger sizes, affecting human health and the climate. In this study, we investigate aerosol size distributions at two stations located close to each other ( 20 km) but at different altitudes: urban (UGR; 680ma.s.l., metres above sea level) and high-altitude remote (SNS; 2500ma.s.l.) sites, both in the area of Granada, Spain, and part of AGORA observatory (Andalusian Global ObseRvatory of the Atmosphere). The analysis shows a significant contribution of nucleation mode aerosol particles to the total aerosol number concentration at both sites, with a contribution of 47% and 48% at SNS and UGR, respectively. Due to the important contribution of NPF events to the total aerosol number concentrations and their high occurrence frequency (>70 %) during the study period, a detailed analysis of NPF events is done in order to get insight into the possible mechanisms and processes involved in NPF events at these contrastive sites. At SNS, NPF is found to be associated with the transport of gaseous precursors from lower altitudes by orographic buoyant upward flows. NPF events at the SNS site are always observed from the smallest measured sizes of the aerosol size distribution (4 nm), implying that NPF takes place in or in the vicinity of the high-altitude SNS station rather than being transported from lower altitudes. Although NPF events at the mountain site seem to be connected with those occurring at the urban site, growth rates (GRs) at SNS are higher than those at the UGR site (GR7-25 of 6.9 and 4.5 nm h-1 and GR4-7 of 4.1 and 3.6 nm h-1 at SNS and UGR, respectively). This fact could have special importance for the production of cloud condensation nuclei (CCN) and therefore for cloud formations which may affect regional/global climate, since larger GRs at mountain sites could translate to a larger survival probability of NPF particles reaching CCN sizes, due to the shorter time period needed for the growth. The analysis of sulfuric acid (H2SO4) shows that the contribution of H2SO4 is able to explain a minimal fraction contribution to the observed GRs at both sites (<1%and <10%for the 7–25 and 4–7 nm size ranges, respectively), indicating that other condensing vapours are responsible for the majority of particle growth, as well as the differing growth rates between the two sites. Results also show that the condensation sink (CS) does not play a relevant role in NPF processes at both sites and points to the availability of volatile organic compounds (VOCs) as one of the main factors controlling the NPF events at both sites. Finally, a closer analysis of the NPF events that were observed at the SNS site during a Saharan dust episode that occurred during the field campaign was carried out, evidencing the role of TiO2 and F2O3 together with VOCs in promoting new particle formation during this dust intrusion event. Although further investigation is needed to improve our understanding in this topic, this result suggests that climate effects of mineral dust and NPF are not disconnected from each other as it was commonly thought. Therefore, since mineral dust contributes to a major fraction of the global aerosol mass load, dust–NPF interaction should be taken into account in global aerosol-climate modelling for better climate change prediction. ; Spanish Ministry of Economy and Competitiveness BES2017-080015 CGL2016-81092-R CGL2017-90884-REDT RTI2018-097864-B-I00 ; Andalusian Regional Government P18-RT-3820 ; European Union (EU) 654109 871115 689443 ; Academy of Finland 311932 307537 328616 329274

A large part of the European population is still exposed to ambient nitrogen dioxide (NO2) levels exceeding the European Union (EU) air quality standards, being a key challenge to reduce NO2 concentrations across many European urban areas, particularly close to roads. In this work, a trend analysis of pollutants involved in NO2 processes was done for the period 2003–2014 in traffic sites fromthree Spanish cities (Barcelona,Madrid and Granada) that still exceed the European NO2 air quality standard limits. We also estimated the contributions of primary NO2 emissions and photo-chemically formed NO2 to the observed ambient NO2 concentrations in order to explore their possible role in the observedNO2 concentration trends. TheNOx andNOconcentrations at these traffic sites showed significant decreasing trends during the period 2003–2014, especially at Barcelona (BARTR) andMadrid (MADTR) traffic stations. The NO2 concentrations showed statistically significant downward trends at BARTR and MADTR and remained unchanged at Granada traffic station (GRATR) during the study period. Despite the significant decrease in NO2 concentrations in BCNTR and MADTR during the analysed period, the NO2 concentrations observed over these sites still above the annual NO2 standard limit of 40 μg m−3 and, therefore, more efficient measures are still needed. Primary NO2 emissions significantly influence NO2 concentrations at the three analysed sites. However, as no drastic changes are expected in the after-exhaust treatment technology that can reduce primary NO2 emissions to zero in the near future, only a substantial reduction in NOx emissions will help to comply with the NO2 European air quality standards. Reduction of 78%, 56% and 16% on NOx emissions in Barcelona,Madrid and Granada were estimated to be necessary to comply with the NO2 annual limit of 40 μg m−3.

This work was supported by the Spanish Ministry of Economy and Competitiveness through projects PID2020-120015RB-100, CGL201681092-R, and CGL2017-90884-REDT, by the Andalusia Regional Government through project P18-RT-3820 and P20-00136, by the European Union's Horizon 2020 research and innovation program through project ACTRIS-2 (grant agreement No 654109). This research was partially supported by Project RTI2018.101154.A.I00 funded by MCIN/AEI/10.13039/501100011033/FEDER "Una manera de hacer Europa". The authors thank the Parque de la Ciencias for making this research possible. Juan Andr ' es Casquero-Vera is supported by BES-2017-080015 funded by MCIN/AEI/10.13039/501100011033 and FSE "El FSE invierte en tu futuro". Funding for open access charge: Universidad de Granada/CBUA. ; Although cities are an important source of aerosol particles, aerosol number flux measurements over urban areas are scarce. These measurements are however important as they can allow us to identify the different sources/sinks of aerosol particles and quantify their emission contributions. Therefore, they can help us to understand the aerosol impacts on human health and climate, and to design effective mitigation strategies through the reduction of urban aerosol emissions. In this work we analyze the aerosol number concentrations and fluxes for particles with diameters larger than 2.5 nm measured by eddy covariance technique at an urban area (Granada city, Spain) from November 2016 to April 2018. This is the first study of particle number flux in an urban area in the Iberian Peninsula and is one of the few current studies that report long-term aerosol number flux measurements. The results suggest that, on average, Granada urban area acted as a net source for atmospheric aerosol particles with median particle number flux of 150 x 10(6) m(-2) s(-1). Downward negative fluxes were observed in only 12% of the analyzed data, and most of them were observed during high aerosol load conditions. Both aerosol number fluxes and concentrations were ...

In this study, aerosol light-absorption measurements obtained at three sites during a winter campaign were used to analyse and identify the major sources of Black Carbon (BC) particles in and around the Alhambra monument, a UNESCO World Heritage Site that receives over 2 million visitors per year. The Conditional Bivariate Probability Function and the Aethalometer model were employed to identify the main sources of BC particles and to estimate the contributions of biomass burning and fossil fuel emissions to the total Equivalent Black Carbon (EBC) concentrations over the monumental complex. Unexpected high levels of EBC were found at the Alhambra, comparable to those measured in relatively polluted European urban areas during winter. EBC concentrations above 3.0 μg/m3, which are associated with unacceptable levels of soiling and negative public reactions, were observed at Alhambra monument on 13 days from 12 October 2015 to 29 February 2016, which can pose a risk to its long-term conservation and may cause negative social and economic impacts. It was found that road traffic emissions from the nearby urban area and access road to the Alhambra were the main sources of BC particles over the monument. However, biomass burning emissions were found to have very small impact on EBC concentrations at the Alhambra. The highest EBC concentrations were observed during an extended stagnant episode associated with persistent high-pressure systems, reflecting the large impact that can have these synoptic conditions on BC over the Alhambra. ; European Union's Horizon 2020 Research and Innovation Programme under grant agreement No. 654109, ACTRIS-2. ; Spanish Ministry of Economy and Competitiveness and FEDER through project CGL2013-45410-R, CGL2016-81092-R 598 and CGL2012-30729. ; Andalusia Regional Government through project P12- RNM-2409 and P12-FQM-1889.

This work was supported by the Spanish Ministry of Economy and Competitiveness through projects CGL2016-81092-R, PID2020-120015RB-I00 and RTI2018-101154-A-I00, the Regional Government of Andalusia through project AEROPRE (P18-RT-3820), and by the Spanish Ministry of Education, Culture and Sports and Spanish Ministry of universities through grant FPU19/05340. The financial support for EARLINET in the ACTRIS.IMP 871115 (H2020-INFRADEV-2018-2020) is gratefully acknowledged. This work is related to activities within the COST Action CA18235 PROBE (PROfiling the atmospheric Boundary layer at European scale). The authors thank the University of Granada, Programa Operativo FEDER Andalucia 2014-2020 through project DEM3TRIOS (A-RNM-430-UGR20). Juan Antonio Bravo-Aranda received funding from the Marie Skodowska-Curie Action Cofund 2016 EU project-Athenea3i under grant agreement no. 754446. Maria J. Granados-Munoz project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skodowska-Curie grant agreement No 796539. The financial support for UGR and FEDER funds through project B-RNM-496-UGR18 is gratefully acknowledged. ; Aerosol-cloud interactions (ACI) are in the spotlight of atmospheric science since the limited knowledge about these processes produces large uncertainties in climate predictions. These interactions can be quantified by the aerosol-cloud interaction index (ACI index), which establishes a relationship between aerosol and cloud microphysics. The experimental determination of the ACI index through a synergistic combination of lidar and cloud radar is still quite challenging due to the difficulties in disentangling the aerosol influence on cloud formation from other processes and in retrieving aerosol-particle and cloud microphysics from remote sensing measurements. For a better understanding of the ACI and to evaluate the optimal experimental conditions for the measurement of these processes, a Lidar and Radar Signal Simulator (LARSS) is presented. ...

An experimental setup to study aerosol hygroscopicity is proposed based on the temporal evolution of attenuated backscatter coefficients from a ceilometer colocated with an instrumented tower equipped with meteorological sensors at different heights. This setup is used to analyze a 4.5-year database at the ACTRIS SIRTA observatory in Palaiseau (Paris, France, 2.208 E, 48.713 N; 160m above sea level). A strict criterion-based procedure has been established to identify hygroscopic growth cases using ancillary information, such as online chemical composition, resulting in 8 hygroscopic growth cases from a total of 107 potential cases. For these eight cases, hygroscopic growth-related properties, such as the attenuated backscatter enhancement factor fbeta (RH) and the hygroscopic growth coefficient y, are evaluated. This study shows that the hygroscopicity parameter y is negatively correlated with the aerosol organic mass fraction but shows a positive correlation with the aerosol inorganic mass fraction. Among inorganic species, nitrate exhibited the highest correlation. This is the first time that hygroscopic enhancement factors are directly retrieved under ambient aerosols using remotesensing techniques, which are combined with online chemical composition in situ measurements to evaluate the role of the different aerosol species in aerosol hygroscopicity. ; This work was supported by the Andalusia Regional Government through project P12-RNM-2409; the Spanish Ministry of Economy and Competitiveness through projects CGL2013-45410-R, CGL2016-81092-R, and CGL2017-83538-C3- 1-R; the Excellence network CGL2017-90884-REDT; the Juan de la Cierva grant IJCI-2016-29838; and the University of Granada trough the Plan Propio Program P9 Call-2013 contract and project UCE-PP2017. Andrés Esteban Bedoya-Velásquez has been supported by a grant for PhD studies in Colombia, COLCIENCIAS (Doctorado Nacional – 647), associated with the Physics Sciences program at the Universidad Nacional de Colombia, Sede Medellín, and the Asociación Universitaria Iberoamericana de Postgrado (AUIP). Financial support for EARLINET was provided through ACTRIS-2 Research Infrastructure Project EU H2O20 (grant agreement no. 654109), particularly for staying 2 weeks at SIRTA observatory and developing this investigation (TNA 3 SIR AHEAAARS). The authors gratefully acknowledge the FEDER program for the instrumentation used in this work. Juan Antonio Bravo-Aranda has received funding from the Marie Sklodowska-Curie Action Cofund 2016 EU project – Athenea3i under grant agreement no. 754446.

This study evaluates the potential of the GRASP algorithm (Generalized Retrieval of Aerosol and Surface Properties) to retrieve continuous day-to-night aerosol properties, both column-integrated and vertically resolved. The study is focused on the evaluation of GRASP retrievals during an intense Saharan dust event that occurred during the Sierra Nevada Lidar aerOsol Profiling Experiment I (SLOPE I) field campaign. For daytime aerosol retrievals, we combined the measurements of the ground-based lidar from EARLINET (European Aerosol Research Lidar Network) station and sun–sky photometer from AERONET (Aerosol Robotic Network), both instruments co-located in Granada (Spain). However, for night-time retrievals three different combinations of active and passive remote-sensing measurements are proposed. The first scheme (N0) uses lidar night-time measurements in combination with the interpolation of sun–sky daytime measurements. The other two schemes combine lidar night-time measurements with nighttime aerosol optical depth obtained by lunar photometry either using intensive properties of the aerosol retrieved during sun–sky daytime measurements (N1) or using the Moon aureole radiance obtained by sky camera images (N2). ; This research has been supported by the European Union through the H2020 programme (ACTRIS-2, grant no. 654109) and the Spanish Ministry of Economy and Competitiveness (projects CMT2015-66742-R, CGL2016-81092- R, CGL2017-85344-R, RTI2018-097864-B-I00 and CGL2017- 90884-REDT).

Biomass burning (BB) is a significant source of atmospheric particles in many parts of the world. Whereas many studies have demonstrated the importance of BB emissions in central and northern Europe, especially in rural areas, its impact in urban air quality of southern European countries has been sparsely investigated. In this study, highly time resolved multi-wavelength absorption coefficients together with levoglucosan (BB tracer) mass concentrations were combined to apportion carbonaceous aerosol sources. The Aethalometer model takes advantage of the different spectral behaviour of BB and fossil fuel (FF) combustion aerosols. The model was found to be more sensitive to the assumed value of the aerosol Ångström exponent (AAE) for FF (AAEff) than to the AAE for BB (AAEbb). As result of various sensitivity tests the model was optimized with AAEff = 1.1 and AAEbb = 2. The Aethalometer model and levoglucosan tracer estimates were in good agreement. The Aethalometer model was further applied to data from three sites in Granada urban area to evaluate the spatial variation of CMff and CMbb (carbonaceous matter from FF or BB origin, respectively) concentrations within the city. The results showed that CMbb was lower in the city centre while it has an unexpected profound impact on the CM levels measured in the suburbs (about 40%). Analysis of BB tracers with respect to wind speed suggested that BB was dominated by sources outside the city, to the west in a rural area. Distinguishing whether it corresponds to agricultural waste burning or with biomass burning for domestic heating was not possible. This study also shows that although traffic restrictions measures contribute to reduce carbonaceous concentrations, the extent of the reduction is very local. Other sources such as BB, which can contribute to CM as much as traffic emissions, should be targeted to reduce air pollution. ; This research was partially supported by the Andalusia Regional Government through projects P10-RNM-6299 and P12-RNM-2409, by the Spanish Ministry of Economy and Competitiveness and FEDER through project CGL2013_45410-R; by EUREKA and the Slovenian Ministry of Economic Development and Technology grants (Eurostars grant E!4825 FC Aeth, JR-KROP grant 3211-11-000519); and by European Union's Horizon 2020 Research and Innovation Programme under grant agreement No. 654109, ACTRIS-2. The authors would like to thank Air Quality Service from Junta de Andalucía (Consejería de Medio Ambiente y Ordenación del Territorio) and Vicerrectorado de Política Científica e Investigación from the University of Granada for their support in the installation of the Aethalometer at PC and GV, respectively. ; G. Titos was partially funded by Programa del Plan Propio de Investigación "Contrato Puente" of the University of Granada and by the Spanish Ministry of Economy and Competitiveness under postdoctoral program Juan de la Cierva – Formación (FJCI-2014-20819).

The interest in the use of ceilometers for optical aerosol characterization has increased in the last few years. They operate continuously almost unattended and are also much less expensive than lidars; hence, they can be distributed in dense networks over large areas. However, due to the low signal-to-noise ratio it is not always possible to obtain particle backscatter coefficient profiles, and the vast number of data generated require an automated and unsupervised method that ensures the quality of the profiles inversions. In this work we describe a method that uses aerosol optical depth (AOD) measurements from the AERONET network that it is applied for the calibration and automated quality assurance of inversion of ceilometer profiles. The method is compared with independent inversions obtained by co-located multiwavelength lidar measurements. A difference smaller than 15ĝ in backscatter is found between both instruments. This method is continuously and automatically applied to the Iberian Ceilometer Network (ICENET) and a case example during an unusually intense dust outbreak affecting the Iberian Peninsula between 20 and 24 February 2016 is shown. Results reveal that it is possible to obtain quantitative optical aerosol properties (particle backscatter coefficient) and discriminate the quality of these retrievals with ceilometers over large areas. This information has a great potential for alert systems and model assimilation and evaluation. © 2017 Author(s). ; Acknowledgements. This work was supported by the Spanish Ministry of Economy and Competitiveness through projects CGL2012-39623-C02-01, CGL2013-45410-R, CGL2014-56255-C2-1-R, CMT2015-66742-R, CGL2015-70741-R, CGL2015-73250-JIN and CGL2016-81092-R; by the regional government of Andalusia through project P12-RNM-2409; by the regional government of Castilla y Leon through project VA100U14; by the Junta de Extremadura (Ayuda a Grupos de Investigación GR15137); and by the European Union's Horizon 2020 research and innovation program through project ACTRIS-2 (grant agreement no. 654109). The authors thankfully acknowledge the FEDER program for the instrumentation used in this work. This work was also partially funded by the University of Granada through the contract "Plan Propio. Programa 9. Convocatoria 2013". Marco Pandolfi is funded by a Ramón y Cajal Fellowship (RYC-2013-14036) awarded by the Spanish Ministry of Economy and Competitiveness. The authors would like to acknowledge the valuable contribution through the discussions in the working group meetings organized by COST Action ES1303 (TOPROF). ; Peer reviewed

This is a preprint version of article accepted "Roman, A.; et al. Retrieval of aerosol profiles combining sunphotometer and ceilometer measurements in GRASP code. Atmospheric Research, 204: 161-177 (2018). DOI: https://doi.org/10.1016./j.atmosres.2018.01.021". ; In this paper we present an approach for the profiling of aerosol microphysical and optical properties combining ceilometer and sun/sky photometer measurements in the GRASP code (General Retrieval of Aerosol and Surface Properties). For this objective, GRASP is used with sun/sky photometer measurements of aerosol optical depth (AOD) and sky radiances, both at four wavelengths and obtained from AErosol RObotic NETwork (AERONET), and ceilometer measurements of range corrected signal (RCS) at 1064 nm. A sensitivity study with synthetic data evidences the capability of the method to retrieve aerosol properties such as size distribution and profiles of volume concentration (VC), especially for coarse particles. Aerosol properties obtained by the mentioned method are compared with airborne in-situ measurements acquired during two flights over Granada (Spain) within the framework of ChArMEx/ADRIMED (Chemistry-Aerosol Mediterranean Experiment/Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region) 2013 campaign. The retrieved aerosol VC profiles agree well with the airborne measurements, showing a mean bias error (MBE) and a mean absolute bias error (MABE) of 0.3 µm3/cm3 (12%) and 5.8 µm3/cm3 (25%), respectively. The differences between retrieved VC and airborne in-situ measurements are within the uncertainty of GRASP retrievals. In addition, the retrieved VC at 2500 m a.s.l. is shown and compared with in-situ measurements obtained during summer 2016 at a high-atitude mountain station in the framework of the SLOPE I campaign (Sierra Nevada Lidar AerOsol Profiling Experiment). VC from GRASP presents high correlation (r=0.91) with the in-situ measurements, but overestimates them, MBE and MABE being equal to 23% and 43%. ; This work was supported by the Andalusia Regional Government (project P12-RNM-2409) and by the "Consejería de Educación" of "Junta de Castilla y León" (project VA100U14); the Spanish Ministry of Economy and Competitiveness under the projects, CMT2015-66742-R, CGL2016-81092-R and "Juan de la Cierva-Formación" program (FJCI-2014-22052); and the European Union's Horizon 2020 research and innovation programme through project ACTRIS-2 (grant agreement no 654109) and the Marie Curie Rise action GRASP-ACE (grant agreement no 778349). The authors thankfully acknowledge the FEDER program for the instrumentation used in this work. COST Action TOPROF (ES1303), supported by COST (European Cooperation in Science and Technology), is also acknowledged.

Jose Antonio Benavent-Oltra is funded by the University of Granada through "Plan Propio. Programa 7, Convocatoria 2019". Roberto Roman is funded by MINECO under the postdoctoral programme Juan de la Cierva-Incorporacion (IJCI2016-30007). Juan Andres Casquero-Vera is funded by MINECO under the predoctoral programme FPI (BES-2017-080015). Maria J. Granados-Munoz received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 796539. Oleg Dubovik was supported by the Labex CaPPA project, which is funded by the French National Research Agency under contract "ANR-11-LABX0005-01". This work was also supported by the Spanish Ministry of Economy and Competitiveness (projects CMT2015-66742-R, CGL2016-81092-R, CGL2017-85344-R, RTI2018-097864-B-I00 and CGL2017-90884-REDT), by the Andalusia Regional Government through project P18-RT-3820 and the Unity of Excellence "Maria de Maeztu" (project MDM-2016-0600) financed by the Spanish State Research Agency (AEI). The authors thankfully ac-knowledge the FEDER programme for the instrumentation used in this work, the University of Granada, which supported this study through the Excellence Units Program, and the Sierra Nevada National Park. We also thank Dr. Grisa Monick who provided the Aethalometer AVIO AE-33 installed on the aircraft. Thanks to AERONET and ACTRIS/AERONET Europe for the scientific and technical support. Finally, the authors would like to acknowledge the use of the GRASP inversion algorithm software (http://www.grasp-open.com, last access: 1 April 2020), in this work. ; The Sierra Nevada Lidar aerOsol Profiling Experiment I and II (SLOPE I and II) campaigns were intended to determine the vertical structure of aerosols by remote sensing instruments and test the various retrieval schemes for obtaining aerosol microphysical and optical properties with in situ measurements. The SLOPE I and II campaigns were developed during the summers of 2016 and 2017, respectively, combining active and passive remote sensing with in situ measurements at stations belonging to the AGORA observatory (Andalusian Global ObseRvatory of the Atmosphere) in the Granada area (Spain). In this work, we use the in situ measurements of these campaigns to evaluate aerosol properties retrieved by the GRASP code (Generalized Retrieval of Atmosphere and Surface Properties) combining lidar and sun-sky photometer measurements. We show an overview of aerosol properties retrieved by GRASP during the SLOPE I and II campaigns. In addition, we evaluate the GRASP retrievals of total aerosol volume concentration (discerning between fine and coarse modes), extinction and scattering coefficients, and for the first time we present an evaluation of the absorption coefficient. The statistical analysis of aerosol optical and microphysical properties, both column-integrated and vertically resolved, from May to July 2016 and 2017 shows a large variability in aerosol load and types. The results show a strong predominance of desert dust particles due to North African intrusions. The vertically resolved analysis denotes a decay of the atmospheric aerosols with an altitude up to 5 km a.s.l. Finally, desert dust and biomass burning events were chosen to show the high potential of GRASP to retrieve vertical profiles of aerosol properties (e.g. absorption coefficient and single scattering albedo) for different aerosol types. The aerosol properties retrieved by GRASP show good agreement with simultaneous in situ measurements (nephelometer, aethalometer, scanning mobility particle sizer, and aerodynamic particle sizer) performed at the Sierra Nevada Station (SNS) in Granada. In general, GRASP overestimates the in situ data at the SNS with a mean difference lower than 6 mu m(3) cm(-3) for volume concentration, and 11 and 2 Mm(-1)for the scattering and absorption coefficients. On the other hand, the comparison of GRASP with airborne measurements also shows an overestimation with mean absolute differences of 14 +/- 10 and 1.2 +/- 1.2 Mm(-1) for the scattering and absorption coefficients, showing a better agreement for the absorption (scattering) coefficient with higher (lower) aerosol optical depth. The potential of GRASP shown in this study will contribute to enhancing the representativeness of the aerosol vertical distribution and provide information for satellite and global model evaluation. ; University of Granada ; MINECO under the postdoctoral programme Juan de la Cierva-Incorporacion IJCI2016-30007 ; MINECO under the predoctoral programme FPI BES-2017-080015 ; European Commission 796539 ; French National Research Agency (ANR) ANR-11-LABX0005-01 ; Spanish Ministry of Economy and Competitiveness CMT2015-66742-R CGL2016-81092-R CGL2017-85344-R RTI2018-097864-B-I00 CGL2017-90884-REDT ; Andalusia Regional Government P18-RT-3820 ; Spanish State Research Agency (AEI) MDM-2016-0600 ; Excellence Units Program ; Sierra Nevada National Park

The AEAOD– ΔAEAOD grid proposed by Gobbi et al. (2007) is a graphical method used to visually represent the spectral characterization of aerosol optical depth (AOD), i.e. Angström exponent (AE) and its curvature, in order to infer the fine mode contribution (η) to the total AOD and the size of the fine mode aerosol particles. Perrone et al. (2014) applied this method for the wavelengths widely used in lidar measurements. However, in neither case does the method allow for a direct relationship between η and the fine mode fraction contribution to the total aerosol population. Some discussions are made regarding the effect of shape and composition to the classical AE-ΔAE plot. The potential use of particle backscatter measurements, widely used in aerosol characterization methods together with extinction measurements, is also discussed in the AE-ΔAE grid context. A modification is proposed that yields the submicron contribution to the total volume concentration by using particle extinction data, and a comparison to experimental measurements is made. Our results indicate that the use of a modified AE-ΔAE grid plot to directly obtain submicrometric and micrometric mode fraction to the total aerosol population is feasible if a volume-based bimodal particle size distribution is used instead of a number-based one. ; Andalusia Regional Government through project P12-RNM-2409 ; Spanish Ministry of Sciences, Innovation and Universities (CGL2016-81092 and CGL2017 -90884 - REDT)

This study focuses on the analysis of aerosol hygroscopic growth during the Sierra Nevada Lidar AerOsol Profiling Experiment (SLOPE I) campaign by using the synergy of active and passive remote sensors at the ACTRIS Granada station and in situ instrumentation at a mountain station (Sierra Nevada, SNS). To this end, a methodology based on simultaneous measurements of aerosol profiles from an EARLINET multi-wavelength Raman lidar (RL) and relative humidity (RH) profiles obtained from a multi-instrumental approach is used. This approach is based on the combination of calibrated water vapor mixing ratio (r) profiles from RL and continuous temperature profiles from a microwave radiometer (MWR) for obtaining RH profiles with a reasonable vertical and temporal resolution. This methodology is validated against the traditional one that uses RH from co-located radiosounding (RS) measurements, obtaining differences in the hygroscopic growth parameter (γ) lower than 5% between the methodology based on RS and the one presented here. Additionally, during the SLOPE I campaign the remote sensing methodology used for aerosol hygroscopic growth studies has been checked against Mie calculations of aerosol hygroscopic growth using in situ measurements of particle number size distribution and submicron chemical composition measured at SNS. The hygroscopic case observed during SLOPE I showed an increase in the particle backscatter coefficient at 355 and 532nm with relative humidity (RH ranged between 78 and 98%), but also a decrease in the backscatter-related Ångström exponent (AE) and particle linear depolarization ratio (PLDR), indicating that the particles became larger and more spherical due to hygroscopic processes. Vertical and horizontal wind analysis is performed by means of a co-located Doppler lidar system, in order to evaluate the horizontal and vertical dynamics of the air masses. Finally, the Hänel parameterization is applied to experimental data for both stations, and we found good agreement on γ measured with remote sensing (γ532 0.48 ± 0.01 and γ355 0.40 ± 0.01) with respect to the values calculated using Mie theory (γ532 0.53 ± 0.02 and γ355 0.45 ± 0.02), with relative differences between measurements and simulations lower than 9% at 532nm and 11% at 355nm. © Author(s) 2018. ; Acknowledgements. This work was supported by the Andalusia Regional Government through project P12-RNM-2409; by the Spanish Ministry of Economy and Competitiveness through projects CGL2013-45410-R and CGL2016-81092-R, the excelence network CGL2017-90884-REDT, the FPI grant (BES-2014-068893), and the Juan de la Cierva grants FJCI-2014-22052 and FJCI-2014-20819; by the University of Granada trough the Plan Propio Program P9 Call-2013 contract. Andrés Bedoya has been supported by a grant for PhD studies in Colombia, COLCIEN-CIAS (Doctorado Nacional – 647), associated with the Physics Sciences program at the Universidad Nacional de Colombia, Sede Medellín and Asociación Universitaria Iberoamericana de Postgrado (AUIP). The study has also been supported by the Swiss National Science Foundation trough project PZ00P2_168114. Financial support for EARLINET was through the ACTRIS Research Infrastructure Project EU H2020 (Grant agreement no. 654109), particularly trough the TNA GRA-3 HYGROLIRA. We thank the AERO group from ESRL-GMD at NOAA for providing the CPD software used for routine measurements at the SNS, and for their technical support. The authors gratefully acknowledge the FEDER program for the instrumentation used in this work. ; Peer reviewed