Physical and optical properties of aerosols over an urban location in Spain: seasonal and diurnal variability

Measurements of aerosol optical properties and aerosol number size distribution obtained during the period from December 2005 to November 2007 at Granada, an urban site in south-eastern Spain, are analyzed. Large variations of the measured variables have been found, and related to variations in emissions sources and meteorological conditions. High values of aerosol absorption and scattering coefficients are obtained during winter and low values are measured during summer. This seasonal pattern in the surface aerosol optical properties is opposite to the seasonal cycle showed by columnar aerosol optical depth. The differences in the seasonal features of the surface and column-integrated data are related to seasonal variations in the aerosol vertical distribution, aerosol sources and boundary layer height. In winter the number density of "fine" particles (0.5<particle diameter<1 μm) is significantly larger than in summer while the number density of "coarse" particles (1<particle diameter<20 μm) is slightly larger during summer and spring than during winter and autumn. The scattering Angström exponent, αs, presents an evident seasonal cycle with values of 1.8±0.2, 1.6±0.3, 1.3±0.3 and 1.4±0.3 in winter, spring, summer and autumn, respectively. This suggests the presence of a large fraction of submicron particles at the site, especially during winter. The aerosols measured in this study contain a large fraction of absorbing material as indicated by the average single-scattering albedo that has values of 0.65±0.07, 0.66±0.06, 0.70±0.06 and 0.73±0.06 in autumn, winter, spring and summer, respectively. The aerosol scattering albedo obtained in the surface boundary layer of Granada is below the critical value of 0.86 that determines the shift from cooling to warming. These results put in evidence the need of efforts to reduce absorbing particles (black carbon) emissions to avoid the possible warming that would result from the reductions of the cooling aerosols only. The aerosol absorption and scattering coefficients present a clear diurnal pattern, in all seasons, with two local maxima, one early in the morning and the second one in the evening. This diurnal cycle is mainly attributed to the diurnal evolution of atmospheric boundary layer and local anthropogenic activities.This work was supported by the Spanish Ministry of Science and Technology through projects No: CGL2007-66477-C02-01 and CSD2007-00067 and by the Andalusian Regional Government through projects No: P06-RNM-01503 and P08-RNM-3568

Direct-sun total ozone data from a spectroradiometer: methodology and comparison with satellite observations

A methodology to obtain the total ozone column (TOC) from the direct-sun spectral measurements of a Bentham spectroradiometer located at Granada (Spain) is presented in this paper. The method relies on the differential absorption technique using two pairs of direct irradiance at adjacent wavelengths between 305 and 340 nm. The extraterrestrial constant was determined from the extrapolation to zero air mass of each wavelength pair (Langley plot method). We checked the strong influence of the cloud cover on the Bentham TOC measurements using simultaneous sky images taken with an all-sky camera. Thus, reliable TOC data are exclusively obtained during cloud-free conditions or partly cloudy conditions without the solar disk obstructed. In this work, the hourly TOC averages retrieved by the Bentham instrument with a standard deviation smaller than 3% (~ 10 Dobson Unit) are selected as high-quality TOC data. The analysis of the diurnal TOC variations during cloud-free days in late spring and summer showed different TOC values between the morning and afternoon periods. Thus, while the mornings exhibit an almost stable pattern, the afternoons display a monotonic TOC increase which could be partially related to photochemical processes in the lower troposphere associated with the formation of surface ozone. Finally, the Bentham TOC measurements were compared against the satellite data derived from three satellite instruments: OMI, GOME and SCIAMACHY. The mean absolute values of the relative differences between satellite and ground-based data were smaller than 3%, highlighting the high reliability of the retrieval method proposed in this paper to derive TOC data.This work was partially supported by the Andalusian Regional Government through projects P08-RNM-3568 and P10-RNM-6299, the Ministerio de Ciencia e Innovación through projects CGL2008-05939-C03-02/CLI, CGL2008-05939-C03-03/CLI, CGL2010-18782, CGL-2011-2992-1-C02-01 and CSD2007-00067, and by the European Union through the ACTRIS project (EU INFRA-2010-1.1.16–262254)

Electrodynamic single-particle trap integrated into double-cavity ring-down spectroscopy for light extinction

The study of the interaction of light with matter upon changing environmental conditions requires new platforms that provide accurate and reliable measurements. One suitable technique for studying such interaction uses electrodynamic traps to levitate micro or nanoparticles in combination with an optical interrogation technique, but improvements and new developments that complement spectroscopic information are necessary. Here, we use a Paul Electrodynamic Trap (PET) coupled to a Double-Cavity Ring Down Spectroscopy (D-CRDS) to measure the extinction cross section of single levitated particles at two different wavelengths (405 and 532 nm). The level of control achieved over the motion and stability is such that the particle can be consecutively placed at the central maximum of two independent TEM00 Gaussian modes of the ring-down cavities. Therefore, we can directly measure the dynamic change of the extinction cross section of a single particle at two different wavelengths. The combination of simulations using Mie theory and experiments demonstrates the potential of this robust and versatile setup applied to 1,2,6-hexanetriol particles. Unlike standard methods, our system provides crucial information of drastic and reversible change in the extinction cross-section of a sodium chloride particle in efflorescence and deliquescence points, indicating changes in solute mass, charge, refractive index, sphericity and size during the dehydration and hydration processes.Spanish Ministry of Science and Innovation through projects ELPIS (PID2020-12001-5RB-I00)Junta de Andalucía Excellence projects ADAPNE (P20-00136)AEROPRE (P-18-RT-3820)NANOHYBRID (AFQM-644-UGR20) FEDER Una manera de hacer EuropaEQC2019-006423-Pthe European Union's Horizon 2020 research and innovation program through project ACTRIS.IMP (grant agreement No 871115)ATMO-ACCESS (grant agreement No 22 101008004)ACTRIS-España (RED2022-134824-E)University of Granada Plan Propio through Excellence Research Unit Earth Science and Singular Laboratory AGORA (LS2022-1) programs

Correction of a lunar-irradiance model for aerosol optical depth retrieval and comparison with a star photometer

Spanish Ministry of Science, Innovation and Universities RTI2018-097864-b-I00Spanish Ministry of Economy and Competitiveness CGL2016-81092-R CGL2017-90884-REDTEuropean Union's Horizon 2020 research and innovation programme ACTRIS IMP 871115Andalusia Regional Government P18-RT-382

Colorimetric analysis of outdoor illumination across varieties of atmospheric conditions

© 2016 [year] Optical Society of America.]. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited.Solar illumination at ground level is subject to a good deal of change in spectral and colorimetric properties. With an aim of understanding the influence of atmospheric components and phases of daylight on colorimetric specifications of downward radiation, more than 5,600,000 spectral irradiance functions of daylight, sunlight, and skylight were simulated by the radiative transfer code, SBDART [Bull. Am. Meteorol. Soc. 79, 2101 (1998).], under the atmospheric conditions of clear sky without aerosol particles, clear sky with aerosol particles, and overcast sky. The interquartile range of the correlated color temperatures (CCT) for daylight indicated values from 5712 to 7757 K among the three atmospheric conditions. A minimum CCT of ∼3600 K was found for daylight when aerosol particles are present in the atmosphere. Our analysis indicated that hemispheric day-light with CCT less than 3600 K may be observed in rare conditions in which the level of aerosol is high in the atmosphere. In an atmosphere with aerosol particles, we also found that the chromaticity of daylight may shift along the green–purple direction of the Planckian locus, with a magnitude depending on the spectral extinction by aerosol particles and the amount of water vapor in the atmosphere. The data analysis showed that an extremely high value of CCT, in an atmosphere without aerosol particles, for daylight and skylight at low sun, is mainly due to the effect of Chappuis absorption band of ozone at ∼600 nm. In this paper, we compare our data with well-known observations from previous research, including the ones used by the CIE to define natural daylight illuminants.Andalusian Regional Government (P12-RNM-2409); Spanish Ministry of Science and Technology (CGL2013-45410-R); EU via the ACTRIS project (EU INFRA-2010-1.1.16-262254); Spanish Ministry of Economy and Competitiveness (DPI2011-23202)

Columnar aerosol properties from sun-and-star photometry: statistical comparisons and day-to-night dynamic

This work presents the first analysis of long-term correlative day-to-night columnar aerosol optical properties. The aim is to better understand columnar aerosol dynamic from ground-based observations, which are poorly studied until now. To this end we have used a combination of sun-and-star photometry measurements acquired in the city of Granada (37.16° N, 3.60° W, 680 m a.s.l.; South-East of Spain) from 2007 to 2010. For the whole study period, mean aerosol optical depth (AOD) around 440 nm (± standard deviation) is 0.18 ± 0.10 and 0.19 ± 0.11 for daytime and nighttime, respectively, while the mean Angström exponent (α) is 1.0 ± 0.4 and 0.9 ± 0.4 for daytime and nighttime. The ANOVA statistical tests reveal that there are no significant differences between AOD and α obtained at daytime and those at nighttime. Additionally, the mean daytime values of AOD and α obtained during this study period are coherent with the values obtained in the surrounding AERONET stations. On the other hand, AOD around 440 nm present evident seasonal patterns characterised by large values in summer (mean value of 0.20 ± 0.10 both at daytime and nighttime) and low values in winter (mean value of 0.15 ± 0.09 at daytime and 0.17 ± 0.10 at nighttime). The Angström exponents also present seasonal patterns, but with low values in summer (mean values of 0.8 ± 0.4 and 0.9 ± 0.4 at day- and night-time) and relatively large values in winter (mean values of 1.2 ± 0.4 and 1.0 ± 0.3 at daytime and nighttime). These seasonal patterns are explained by the differences in the meteorological conditions and by the differences in the strength of the aerosol sources. To take more insight about the changes in aerosol particles between day and night, the spectral differences of the Angström exponent as function of the Angström exponent are also studied. These analyses reveal increases of the fine mode radius and of the fine mode contribution to AOD during nighttime, being more remarkable in the summer seasons. These variations are explained by the changes of the local aerosol sources and by the meteorological conditions between daytime and nighttime, as well as aerosol aging processes. Case studies during summer and winter for different aerosol loads and types are also presented to clearly illustrate these findings.This work was supported by the Spanish Ministry of Science and Technology through projects CGL2008-01330-E/CLI (Spanish Lidar Network), CGL2010-18782, CSD2007-00067 and CGL2011-13580-E/CLI; by the Andalusian Regional Government through projects P10-RNM-6299 and P08-RNM-3568; by the EU ACTRIS project (EU INFRA-2010-1.1.16-262254), and by the Postdoctoral Programme of the University of Granada

Aerosol radiative forcing during African desert dust events (2005–2010) over Southeastern Spain

The daily (24 h) averages of the aerosol radiative forcing (ARF) at the surface and the top of the atmosphere (TOA) were calculated during desert dust events over Granada (southeastern Spain) from 2005 to 2010. A radiative transfer model (SBDART) was utilized to simulate the solar irradiance values (0.31–2.8 μm) at the surface and TOA, using as input aerosol properties retrieved from CIMEL sun photometer measurements via an inversion methodology that uses the sky radiance measurements in principal plane configuration and a spheroid particle shape approximation. This inversion methodology was checked by means of simulated data from aerosol models, and the derived aerosol properties were satisfactorily compared against well-known AERONET products. Good agreement was found over a common spectral interval (0.2–4.0 μm) between the simulated SBDART global irradiances at surface and those provided by AERONET. In addition, simulated SBDART solar global irradiances at the surface have been successfully validated against CM-11 pyranometer measurements. The comparison indicates that the radiative transfer model slightly overestimates (mean bias of 3%) the experimental solar global irradiance. These results show that the aerosol optical properties used to estimate ARF represent appropriately the aerosol properties observed during desert dust outbreak over the study area. The ARF mean monthly values computed during desert dust events ranged from −13 ± 8 W m−2 to −34 ± 15 W m−2 at surface, from −4 ± 3 W m−2 to −13 ± 7 W m−2 at TOA and from +6 ± 4 to +21 ± 12 W m−2 in the atmosphere. We have checked if the differences found in aerosol optical properties among desert dust sectors translate to differences in ARF. The mean ARF at surface (TOA) were −20 ± 12 (−5 ± 5) W m−2, −21 ± 9 (−7 ± 5) W m−2 and −18 ± 9 (−6 ± 5) W m−2 for sector A (northern Morocco; northwestern Algeria), sector B (western Sahara, northwestern Mauritania and southwestern Algeria), and sector C (eastern Algeria, Tunisia), respectively. The Kolmogorov-Smirnov statistical test revealed that daily {ARF} values at TOA for sector A were significantly different from the other two sectors, likely as a result of the lower values of single scattering albedo obtained for sector A. The mean values of aerosol radiative forcing efficiency at surface (TOA) were −74 ± 12 W m−2 (−17 ± 7 W m−2) for sector A, −70 ± 14 W m−2 (−20 ± 9 W m−2) for sector B, and −65 ± 16 W m−2 (−22 ± 10 W m−2) for sector C, and thus comparable between the three sectors in all seasons.This work was supported by the Andalusia Regional Government through projects P08-RNM-3568 and P10-RNM-6299, by the Spanish Ministry of Science and Technology through projects CGL2010-18782, CSD2007-00067 and CGL2011-13580-E/CLI; and by EU through ACTRIS project (EU INFRA-2010-1.1.16-262254). The authors thankfully acknowledge the computer resources, technical expertise and assistance provided by the Barcelona Supercomputing Center. ALFA database computation was partly supported by RES (Spanish Supercomputation Network) computing resources (projects AECT-2009-1-0012, AECT-2011-3-0016)

Aerosol number fluxes and concentrations over a southern European urban area

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-REDTAndalusia Regional Government P18-RT-3820 P20-00136European Commission 654109MCIN/AEI/FEDER "Una manera de hacer Europa" RTI2018.101154.A.I00FSE "El FSE invierte en tu futuro"Universidad de Granada/CBUA MCIN/AEI BES-2017-08001

Sensitivity of UV Erythemal Radiation to Total Ozone Changes under Different Sky Conditions: Results for Granada, Spain

This is the peer reviewed version of the following article: Antón, M.; et al. Sensitivity of UV Erythemal Radiation to Total Ozone Changes under Different Sky Conditions: Results for Granada, Spain. Photochemistry and Photobiology, 92(1): 215-219 (2016), which has been published in final form at http://dx.doi.org/10.1111/php.12539 . This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-ArchivingThis paper focuses on the analysis of the sensitivity of UV erythemal radiation (UVER) to variations of the total ozone column (TOC) under different sky conditions at Granada (southeastern Spain). The sensitivity is studied both in relative terms by means of the Radiation Amplification Factor (RAF) and in absolute terms using the Ozone Efficiency (OE). These two variables are determined for diverse sky conditions characterized by the cloud cover information given by a sky camera (in oktas) and the cloud optical depth (COD) estimated from global solar radiation measurements. As expected, in absolute terms, the TOC variations cause substantially smaller UVER changes during completely overcast situations than during cloud-free cases. For instance, the OE (SZA=30º, TOC=290 DU) decreases from 0.68 mW/m2 per unit of TOC (0 oktas) to 0.50 mW/m2 per unit of TOC (8 oktas). However, the opposite is observed when the analysis is performed in relative terms. Thus, the RAF (determined for SZA cases below 80º) increases from 1.1 for cloud-free cases (0 oktas) to 1.4 for completely overcast situations (8 oktas). This opposite behavior is also found when both RAF and OE are analyzed as functions of COD. Thus, while the OE strongly decreases with increasing COD, the RAF increases as COD increases.European Commission Horizon 2020 Research and Innovation Framework Programme through ACTRIS 2 project (H2020-INFRAIA-2014-2015-654109).Spanish Ministry of Economy and Competitiveness through projects CGL2011-29921-C02-01, CGL2013-45410-R, CGL2014-56255-C2-1-R.Andalusia Regional Government through projects P10-RNM-6299 and P12-RNM-2409

Aerosol properties over the western Mediterranean basin: temporal and spatial variability

This study focuses on the analysis of Aerosol Robotic Network (AERONET) aerosol data obtained over Alborán Island (35.90° N, 3.03° W, 15 m a.s.l.) in the western Mediterranean from July 2011 to January 2012. Additional aerosol data from the three nearest AERONET stations (Málaga, Oujda and Palma de Mallorca) and the Maritime Aerosol Network (MAN) were also analyzed in order to investigate the temporal and spatial variations of aerosol over this scarcely explored region. High aerosol loads over Alborán were mainly associated with desert dust transport from North Africa and occasional advection of anthropogenic fine particles from central European urban-industrial areas. The fine particle load observed over Alborán was surprisingly similar to that obtained over the other three nearest AERONET stations, suggesting homogeneous spatial distribution of fine particle loads over the four studied sites in spite of the large differences in local sources. The results from MAN acquired over the Mediterranean Sea, Black Sea and Atlantic Ocean from July to November 2011 revealed a pronounced predominance of fine particles during the cruise period.This work was supported by the Andalusia Regional Government through projects P12-RNM-2409 and P10-RNM-6299, by the Spanish Ministry of Science and Technology through projects CGL2010-18782, and CGL2013-45410-R; and by the EU through ACTRIS project (EU INFRA-2010-1.1.16-262254). CIMEL Calibration was performed at the AERONET-EUROPE calibration center, supported by ACTRIS (European Union Seventh Framework Program (FP7/2007-2013) under grant agreement no. 262254