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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 maximum in winter and 50% larger than those measured in summer due to the increased emissions from domestic heating, burning of residual agricultural waste in the agricultural area surrounding the site, as well as to the lower aerosol dilution effects during winter. The analysis of the seasonal diurnal variability of the aerosol number concentration revealed the significant impact of traffic emissions on aerosol population over Granada urban area in all seasons. It also shows the impact of domestic heating and agricultural waste burning emissions in winter as well as the influence of new particle formation processes in summer and spring seasons. Closer analysis by wind sector demonstrated that both aerosol concentrations and fluxes from urban sector (where high density of anthropogenic sources is located) were lower than those from rural sector (which includes agricultural area but also the main highway of the city). This evidences the strong impact of aerosol emissions from traffic circulating on the highway on aerosol population over our measurement site., Spanish Government PID2020-120015RB-100 CGL201681092-R CGL2017-90884-REDT, Andalusia Regional Government P18-RT-3820 P20-00136, European Commission 654109, MCIN/AEI/FEDER "Una manera de hacer Europa" RTI2018.101154.A.I00, FSE "El FSE invierte en tu futuro", Universidad de Granada/CBUA MCIN/AEI BES-2017-080015

This work focuses on the analysis of the seasonal cycle of temperature and relative humidity (RH) profiles and integrated water vapor (IWV) obtained from microwave radiometer (MWR) measurements over the mid-latitude city of Granada, southern Spain. For completeness the study, the maximum atmospheric boundary layer height (ABLHmax) is also included. To this end, we have firstly characterized the HATPRO-RPG MWR errors using 55 co-located radiosondes (RS) by means of the mean-bias (biasbar) profile and the standard deviation (SDbias) profile classified under all-weather conditions and cloud-free conditions. This characterization pointed out that temperature from HATPRO-MWR presents a very low biasbar respects RS mostly below 2.0 km agl, ranging from positive to negative values under all-weather conditions (from 1.7 to -0.4 K with SDbias up to 3.0 K). Under cloud-free conditions, the bias was very similar to that found under all-weather conditions (1.8 to -0.4 K) but with smaller SDbias (up to 1.1 K). The same behavior is also seen in this lower part (ground to 2.0 km agl) for RH. Under all-weather conditions, the mean RH bias ranged from 3.0 to -4.0% with SDbias between 10 and 16.3% while under cloud-free conditions the bias ranged from 2.0 to -0.4% with SDbias from 0.5 to 13.3%. Above 2.0 km agl, the SDbias error increases considerably up to 4 km agl (up to -20%), and then decreases slightly above 7.0 km agl (up to -5%). In addition, IWV values from MWR were also compared with the values obtained from the integration of RS profiles, showing a better linear fit under cloud-free conditions (R2 = 0.96) than under all-weather conditions (R2 = 0.82). The mean bias under cloud-free conditions was -0.80 kg/m2 while for all-weather conditions it was -1.25 kg/m2. Thus, the SDbiasfor all the statistics (temperature, RH and IWV) of the comparison between MWR and RS presented higher values for all-weather conditions than for cloud-free conditions ones. It points out that the presence of clouds is a key factor to take into account when MWR products are used. The second part of this work is devoted to a seasonal variability analysis over five years, leading us to characterize thermodynamically the troposphere over our site. This city atmosphere presents a clear seasonal cycle where temperature, ABLHmax and IWV increase from winter to summer and decrease in autumn, meanwhile RH decreases along the warmer seasons. This city presents cold winters (mean daily maximum temperature: 10.6 ± 1.1 °C) and dry/hot summers (mean daily maximum temperature of 28.8 ± 0.9 °C and mean daily maximum of surface RH up to 55.0 ± 6.0%) at surface (680 m asl). Moreover, considering temporal trends, our study pointed out that only temperature and RH showed a linear increase in winters with a mean-rate of (0.5 ± 0.1) °C/year and (3.4 ± 1.7) %/year, respectively, from ground to 2.0 km agl, meanwhile IWV presented a linear increase of 1.0 kg·m-2/year in winters, 0.78 kg·m-2/year in summers and a linear decrease in autumns of -0.75 kg·m-2/year., Andalusia Regional Government through project P12-RNM-2409, Spanish Ministry of Economy and Competitiveness through projects CGL2013-45410-R, CGL2015-73250-JIN and CGL2016-81092-R, Juan de la Cierva grant IJCI-2016-30007

This work has been funded by the excellence research program of the Andalusian Regional Government, grant number P18RT-1854, the National Plan of Scientific and Technical Research and Innovation of the Spanish Ministry of Science and Innovation, grant number RTI2018-095330-B-100 (LEONIDAS), and the "Center of Excellence Severo Ochoa" award to the Instituto de Astrofisica de Andalucia (SEV-2017-0709) by the Spanish State Agency for Research. J.C.G.M acknowledges financial support from the Ramon y Cajal Program of the Spanish Ministry of Science and Innovation (RYC-2016-19570). JoseLuis de la Rosa, JoseAntonio Ruiz and Shi Zongbo are acknowledged for collecting the Sahara-OSN and GobiBeijing desert dust samples., Atmospheric aerosols play key roles in climate and have important impacts on human activities and health. Hence, much effort is directed towards developing methods of improved detection and discrimina- tion of different types of aerosols. Among these, light scattering-based detection of aerosol offers several advantages including applications in both in situ and remote sensing devices. In this work, new scat- tering matrix measurements for two samples of airborne desert dust collected in Spain and China are reported. The average extrapolated scattering matrices of airborne desert dust and of volcanic ash at two wavelengths have been calculated and compared with the aim of finding criteria to distinguish these two types of aerosol. Additionally, the scattering matrix of cypress pollen has been measured and extrapo- lated to explore differences with mineral dust that can be exploited in atmospheric detection. Field mea- surements of the backscattering linear depolarization ratio δL (180 °) are used to obtain information about non-sphericity and discrimination between fine and coarse aerosol. However, the average δL (180 °) for the three types of aerosols considered in this work in the visible spectral range is δL (180 °) = 0.40 ±0.05. This shows that δL (180 °) is not informative about the composition or morphology of irregular particles. By contrast, measurements of scattering matrix elements or depolarization ratios at different scattering angles may provide information about the structural differences of particles, and in particular may en- able to differentiate airborne volcanic ash from desert dust, which are otherwise similar in terms of size and optical constants. Cypress pollen shows a characteristic degree of linear polarization curve that is very different from that of polydisperse irregular mineral dust. Light scattering field instruments and re- mote sensing methods could extract more information about the characteristics of aerosol particles if modifications were introduced to measure the phase curves of several scattering matrix elements or de- polarization ratios., excellence research program of the Andalusian Regional Government P18RT-1854, National Plan of Scientific and Technical Research and Innovation of the Spanish Ministry of Science and Innovation RTI2018-095330-B-100, Spanish State Agency for Research SEV-2017-0709, Spanish Government RYC-2016-19570

The Sierra Nevada Lidar aerOsol Profiling Experiment I and II (SLOPE I and II) campaigns were intended to determine the vertical structure of the aerosol by remote sensing instruments and test the various retrieval schemes for obtaining aerosol microphysical and optical properties with in-situ measurements. These campaigns deployed a set of in-situ and remote sensing instruments at the stations include in AGORA observatory (Andalusian Global ObseRvatory of the Atmosphere) in the Granada area (Spain) along summer in 2016 and 2017. In this work, using the in-situ measurements performed at a high-altitude station, Sierra Nevada station, and airborne flights, we evaluate the retrievals of aerosol properties by GRASP code (Generalized Retrieval of Atmosphere and Surface Properties) combining lidar and sun-sky photometer measurements. Besides, we show an overview of aerosol properties retrieved by GRASP during SLOPE I and II campaigns. 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 absorption coefficient. The statistical analysis of the 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 the North African intrusions. The vertically-resolved analysis denotes a decay of the atmospheric aerosols with altitude up to 5 km a.s.l. Finally, two events of desert dust and biomass burning were used to show the high potential of GRASP to retrieve and study the aerosol properties profiles such as absorption coefficient and single scattering albedo for different aerosol types. The aerosol properties retrieved by GRASP show good agreement with simultaneous in situ measurements performed at Sierra Nevada Station (SNS) in Granada. In general, GRASP overestimates the in situ data at SNS with a mean difference lower than 6 µm3/cm3 for volume concentration, 11 Mm−1 and 2 Mm−1 for scattering and absorption coefficient. On the other hand, the comparison of GRASP with airborne measurements also shows an overestimation with mean absolute differences of 14 ± 10 Mm−1 and 1.2 ± 1.2 Mm−1 for scattering and absorption coefficients, showing a better agreement for absorption (scattering) coefficient with higher (lower) aerosol optical depth. The potentiality of GRASP showed in this study will contribute to enhancing the representativeness of the aerosol vertical distribution and provide information for satellite and global model evaluation.

Rigorous knowledge of the optical fingerprint of droplets is imperative for the understanding of complex aerosol processes. Here, a Paul trap is operated to store single semi-volatile organic droplets in air. The droplets are illuminated with a green laser and the elastic scattering is collected on a CMOS camera. The setup provides excellent performance in terms of confinement and stability, allowing us to detect size changes of the order of few nanometres. The stability also allows us to measure vapour pressures with remarkable reproducibility. This approach supplies a robust method for the optical interrogation in the sub-micron range., Horizon 2020 Framework Programme 654109 871115 754446, IISTA Research Centre, Universidad de Granada C-FQM-410-UGR18, Andalusia Regional Government P18-RT-3820, Spanish Government CGL2016-81092-R CGL2017-90884-REDT PGC2018-098770-B-I00 RTI2018-097864-BI00, Universidad de Granada (Athenea3i)

The simultaneous aerosol sampling at two heights in southern Spain may provide valuable information on the vertical structure of the dust transport from North Africa to the Iberian Peninsula. It also allows the characterization of the ambient air at two sites with distinct anthropogenic impact. This work presents the results obtained from the first field campaign of the FRESA project (Impact of dust-laden African air masses and of stratospheric air masses in the Iberian Peninsula. Role of the Atlas Mountains), performed in the period July-November 2017 at El Albergue Universitario in Sierra Nevada (2550 m a.s.l.) and the city of Granada (650 m a.s.l.). The two sites were instrumented with a low-volume sampler with PM10 inlet for daily sampling and mass and chemical composition characterization, a high-volume sampler for total suspended particles (TSP) for weekly sampling and radionuclide activity determination, and with a GRIMM 365 optical particle counter that provides continuously the aerosol size distribution. In Sierra Nevada, daily PM10 concentrations range from 0 to 100 μg m-3 depending mainly on the origin and features of the air masses that reach this high-elevation site. Levels overpassed 50 μg m-3 on 5 days and were lower than 20 μg m-3 on 90 days. The impact of dust-laden African airflows is particularly intense as dust is transported in most of the cases within well-defined low mid-tropospheric layers. The associated episodic concentrations largely exceed 40 μg m-3. In turn, clean subsiding airflows associated to the polar jet strongly reduce concentrations. In Granada, daily PM10 concentrations are moderately high with values generally between 20 and 40 μg m-3 before the first snows fall over Sierra Nevada. Levels were over 50 μg m-3 on 2 days while they were lower than 20 μg m-3 on 32 days. The highest concentrations do not reach the peaks found at Sierra Nevada. The impact of anthropogenic aerosols of local origin, which are accumulated on high-stability conditions, and also of regional origin (both from the Mediterranean and from the SW Iberian Peninsula) is significant. The contribution of African dust outbreaks superimposes to concentrations in the ambient air and in some events the increase is observed one day after African dust impacts Sierra Nevada. After the first snows over Sierra Nevada, PM10 levels drop and only accumulation periods or African dust events increase concentrations to those before the first snows. Back-trajectories (96-hour, calculated with HYSPLIT using ERA-Interim data of 0.5 degree resolution) show that air flows are quite often decoupled at the two altitudes. Dust-laden African flows reached Sierra Nevada on 33 days; of these, dust was advected poleward over the Atlas near the Algerian-Moroccan border on 19 days and on the remaining 14 it followed a pathway over the Atlantic close to the Moroccan coast. However, only on 3 days air masses of African origin reached Granada. In turn, airflows reaching Granada passed previously over the western Mediterranean Sea on 32 days while only on 3 days Mediterranean flows reached Sierra Nevada. Moreover, the residence time over northern Africa of the air parcels reaching Sierra Nevada while at the same time parcels reaching Granada resided over the Mediterranean is 11,338 hours during the study period. In contrast, the residence time when those reaching Granada resided over Africa is only of 56 hours. This implies that during African dust outbreaks the air masses reaching the study area at the lowest levels do not have African origin but have resided over the Mediterranean. Chemical analysis of the PM10 samples (in progress) while provide the first direct experimental evidence of this fact. The diurnal pattern of both PM10 and particle number concentrations at Granada presents the two typical peaks. Particle concentrations are smaller in winter than in summer, even though in winter the atmospheric boundary layer is shallower and domestic heating is used. Much higher concentrations of coarse (supermicronic) particles are found in summertime during the course of the day. Finer (submicronic) particles present a stronger morning peak (centered about 10 LT) in winter and also concentrations are slightly higher at about 20-21 LT, being quite similar the rest of the day in winter and summer. A number of distinct episodes can be identified: strong African dust impact at Sierra Nevada while Granada is heavily polluted by anthropogenic aerosols (1 August 2017); strong African dust impact at Sierra Nevada which is observed the following day in Granada (15-16 August 2017); African dust outbreaks impacting simultaneously both sites (25 November 2017); episode of accumulation of pollutants at Granada whilst very low concentrations are registered at Sierra Nevada (19-24 November 2017); and fair air quality at both sites (16 September 2017).

The Planetary Boundary Layer (PBL) is the lowermost region of troposphere and endowed with turbulent characteristics, which can have mechanical or thermodynamic origins. Such behavior gives to this layer great importance, mainly in studies about pollutant dispersion and weather forecasting. However, the instruments usually applied in studies about turbulence in the PBL have limitations in spatial resolution (anemometer towers) or temporal resolution (aircrafts). In this study we propose the synergetic use of remote sensing systems (microwave radiometer [MWR], Doppler lidar [DL] and elastic lidar [EL]) to analyze the PBL behavior. Furthermore, we show how some meteorological variables such as air temperature, aerosol number density, vertical wind, relative humidity and net radiation might influence the PBL dynamic. The statistical moments of the high frequency distributions of the vertical velocity, derived from DL and of the backscattered coefficient derived from EL, are corrected by two methodologies, namely first lag and −2/3 correction. The corrected profiles present small differences when compare against the uncorrected profiles, showing low influence of noise and the viability of the proposed methodology. Two case studies were analyzed in detail, one corresponding to a well-defined PBL and another one corresponding to a situation with presence of a Saharan dust lofted aerosol layer and clouds. In both cases the results provided by the different instruments are complementary, thus the synergistic use of the different systems allow us performing a detailed monitoring of the PBL.

In the framework of the project ChArMEx (the Chemistry-Aerosol Mediterranean Experiment, http://charmex.lsce.ipsl.fr/), the variability of aerosol optical, microphysical and radiative properties is examined in three regional background sites on a southwest – northeast (SW–NE) straight line in the middle of the western Mediterranean Basin (WMB). The three sites are on the northward transport pathway of African dust: • Ersa, Corsica Island, France (43.00ºN, 9.36ºW, 80 m a.s.l), • Palma de Mallorca, Mallorca Island, Spain (39.55ºN, 2.62ºE, 10 m a.s.l) and • Alborán, Alboran Island, Spain (35.94ºN, 3.04ºW, 15 m a.s.l). AERONET (AErosol RObotic NETwork) sun-photometer products are mainly used. A preliminary analysis shows that at Ersa and Palma sites the annual aerosol optical depth (AOD) has a similar trend with a peak around 0.2 in July. The winter/spring AOD is lower in Palma than in Ersa, while it is reverse in summer/autumn. The aerosol particle size distribution (and the coarse mode fraction) shows clearly the SW–NE gradient with a decreasing coarse mode peak (and a decreasing coarse mode fraction from 0.5 - 0.35 - 0.2 in July) along the axis Alborán - Palma de Mallorca - Ersa. In addition to the seasonal and annual variability analysis, the analysis of AERONET products is completed with a large variety of ground-based and sounding balloons remote sensing and in situ instruments during the Special Observation Period (SOP) of the ADRIMED campaign in June 2013. The second part of the presentation will focus on the comparison of the observations at Palma de Mallorca and Ersa of the same long-range transported airmasses. The observations include lidar vertical profiles, balloon borne OPC (Optical Particle Counter) and MSG/SEVIRI AOD, among others.

A technique has been developed to detect and map fire growth by using a multitemporal multispectral analysis of AVHRR images. The application of this technique allows fire growth monitoring. The technique is mainly based on comparison of brightness temperature differences and AVHRR Channels 3 and 4 for successive images. It provides a rapid evaluation of the area affected by the fire but suppresses the ambiguous thermal signal produced by nonvegetated terrain. It has been applied to a set of diurnal images acquired by the Granada University AVHRR reception system during a severe fire outbreak in Spain (July 1994). The Andalusian Regional Government Environmental Directorate provided the information and boundaries of the fires which are used as “ground truth” to validate the AVHRR-derived fires boundaries. Both the derived boundaries for the burned area and the fire evolution agree closely with the information collected by field observers, with differences ranging from 9% to 20% in the total burnt area. The availability of 24-h field reports for one of the fires provided an appropriate test for the continuous monitoring by means of remote sensing technique. The study area, located in southeastern Spain, is characterized by a dry mediterranean climate, and the fires affected different ecosystems, from coniferous forest to shrubland. This variety of land coverage makes difficult the application of other proposed techniques.

During the summer 2006 an extended observational campaign of atmospheric aerosol has been developed in the area of Granada, South-eastern Spain. From July to the end of September two Cimel CE-318 radiometers have been operated continuously, one at Andalusian Centre for Environmental Studies (CEAMA), located in the urban area of Granada, a non-industrialized medium size city (37.16oN, 3.61oW and 680 m a.m.s.l.), and the second one at the Astronomical Observatory of Sierra Nevada (37.06oN, 3.38oW and 2896 m a.m.s.l.), with a short horizontal separation between stations that allows us to consider both instrument located in approximately the same vertical column. The Cimel CE-318 measurements have been used to retrieve the aerosol columnar properties, including the columnar volume size distribution, volume scattering phase function, asymmetry factor and single scattering albedo, by means of appropriate inversion procedures. Additionally, at the CEAMA a Raman Lidar system based on a Nd:YAG laser source operating at 1064, 532 and 355 nm and including elastic, polarized and Raman shifted detection has been used to derive profiles of several atmospheric aerosol properties. In this paper we present analyses of the changes and temporal evolution detected in atmospheric aerosol vertical profile. Several long range transport episodes have been detected and back-trajectories analyses and synoptic information have been used in the discussion of results.

Volcanic eruptions are responsible for the injection of SO2 into the stratosphere, and the subsequent production of stratospheric aerosol layer. In June 1991, Mount Pinatubo injected approximately 20 millions metric tons of SO2 into the stratosphere. The volcanic aerosol circled the earth in 21 days, covering an area of about 42% of the earth's surface. A few weeks after the Mount Pinatubo eruption, an abrupt change was detected on the solar radiation flux measurements registered in our radiometric station, located at a sea shore location (36.83°N, 2.41°W, 10 m a.s.l). The Mann-Kendall rank statistic confirms this abrupt change with a high confidence level. We have evaluated the quantitative effect over different terms of solar radiation flux. There is a significant reduction in direct solar radiation of about 10%, while global solar irradiance shows a reduction of about 4%, due to the compensation effect of increasing diffuse irradiance. As in similar analyses carried out in mid-latitude locations, we found a decay of the aerosol effects during the 1992 summer and an enhancement in late 1992., This work was supported by Dirección General de Ciencia y Tecnología fro the Education and Research Ministry of Spain through the project n. PB91-0711.