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Valenzuela A.,University of Évora | Valenzuela A.,University of Granada | Valenzuela A.,Andalusian Institute for Earth System Research IISTA CEAMA | Arola A.,Finnish Meteorological Institute | And 4 more authors.
Atmospheric Research | Year: 2017

This paper provides an account of observed variations in Black carbon (BC) aerosol concentrations and their induced radiative forcing for the first time over Granada a measurement site in Southeastern Iberian Peninsula. Column-integrated BC concentrations were retrieved for the period 2005–2012. Monthly averages of BC concentrations (± one standard deviation) ranged from higher values in January and December with 4.0 ± 2.5 and 4 ± 3 mg/m2, respectively, to lower values in July and August with 1.6 ± 1.2 and 2.0 ± 0.5 mg/m2, respectively. This reduction is not only observed in the average values, but also in the median, third and first quartiles. The average BC concentration in winter (3.8 ± 0.6 mg/m2) was substantially higher than in summer (1.9 ± 0.3 mg/m2), being the eight-year average of 2.9 ± 0.9 mg/m2. The reduction in the use of fossil fuels during the economic crisis contributed significantly to reduced atmospheric loadings of BC. According to our analysis this situation persisted until 2010. BC concentration values were analyzed in terms of air mass influence using cluster analysis. BC concentrations for cluster 1 (local and regional areas) showed high correlations with air masses frequency in winter and autumn. In these seasons BC sources were related to the intense road traffic and increased BC emissions from domestic heating. High BC concentrations were found in autumn just when air mass frequencies for cluster 3 (Mediterranean region) were more elevated, suggesting that air masses coming from that area transport biomass burning particles towards Granada. BC aerosol optical properties were retrieved from BC fraction using aerosol AERONET size volume distribution and Mie theory. A radiative transfer model (SBDART) was used to estimate the aerosol radiative forcing separately for composite aerosol (total aerosols) and exclusively for BC aerosols. The mean radiative forcing for composite aerosol was + 23 ± 6 W/m2(heating rate of + 0.21 ± 0.06 K/day) and + 15 ± 6 W/m2for BC aerosol (heating rate of + 0.15 ± 0.06 K/day). These values of radiative forcing and heating rate for BC aerosol represent about 70% of their values for composite aerosol, which highlights the crucial role that BC aerosols play in modifying the radiation budget and climate. © 2017


Bravo-Aranda J.A.,Andalusian Institute for Earth System Research IISTA CEAMA | Bravo-Aranda J.A.,University of Granada | Titos G.,Andalusian Institute for Earth System Research IISTA CEAMA | Titos G.,University of Granada | And 17 more authors.
Tellus, Series B: Chemical and Physical Meteorology | Year: 2015

Measurements on 27 June 2011 were performed over the Southern Iberian Peninsula at Granada EARLINET station, using active and passive remote sensing and airborne and surface in-situ data in order to study the entrainment processes between aerosols in the free troposphere and those in the planetary boundary layer (PBL). To this aim the temporal evolution of the lidar depolarisation, backscatter-related Angström exponent and potential temperature profiles were used in combination with the PBL contribution to the aerosol optical depth (AOD). Our results show that the mineral dust entrainment in the PBL was caused by the convective processes which 'trapped' the lofted mineral dust layer, distributing the mineral dust particles within the PBL. The temporal evolution of ground-based in-situ data evidenced the impact of this process at surface level. Finally, the amount of mineral dust in the atmospheric column available to be dispersed into the PBL was estimated by means of POLIPHON (Polarizing Lidar Photometer Networking). The dust mass concentration derived from POLIPHON was compared with the coarse-mode mass concentration retrieved with airborne in-situ measurements. Comparison shows differences below 50 μg/m3 (30% relative difference) indicating a relative good agreement between both techniques. © 2015 J. A. Bravo-Aranda et al.


Anton M.,University of Extremadura | Valenzuela A.,University of Granada | Valenzuela A.,Andalusian Institute for Earth System Research IISTA CEAMA | Mateos D.,University of Valladolid | And 7 more authors.
Atmospheric Research | Year: 2014

This paper analyzes the influence of a strong Saharan dust event on longwave (LW) irradiance recorded at Granada (Southeastern Spain) on 6 September 2007. A detailed comparison with shortwave (SW) radiative effects for the same dust event is also shown. For these goals, simultaneous measurements of LW and SW irradiance were used together with the aerosol optical depth at 675nm (AOD675) derived from a Cimel CE-318 sun-photometer. LW irradiance on 6 September (AOD675 ranged between 0.8 and 1.5) increased 8.4% on average compared to a no-dust day (4 September, AOD675 below 0.15), while the SW irradiance was notably reduced about 28.2%. The study also showed that an increase of one unit in the AOD675 led to an increase (decrease) of LW (SW) irradiance of 20 (187) W/m2. Hence, the LW contribution to offset partially the large SW decrease at surface strongly depends on the aerosol load, changing from 40% for AOD675~0.8 to 20% for AOD675~1.5. On daily average, LW radiative effect was about 39% of the SW one and, therefore, the intense decrease of SW irradiance due to dust particles was substantially offset by the increase of the LW irradiance. © 2014 Elsevier B.V.


Sicard M.,Polytechnic University of Catalonia | Barragan R.,Polytechnic University of Catalonia | Dulac F.,French Climate and Environment Sciences Laboratory | Alados-Arboledas L.,University of Granada | And 2 more authors.
Atmospheric Chemistry and Physics | Year: 2016

In the framework of the ChArMEx (the Chemistry-Aerosol Mediterranean Experiment; http://charmex.lsce.ipsl.fr/) program, the seasonal variability of the aerosol optical, microphysical and radiative properties derived from AERONET (Aerosol Robotic Network; http://aeronet.gsfc.nasa.gov/) is examined in two regional background insular sites in the western Mediterranean Basin: Ersa (Corsica Island, France) and Palma de Mallorca (Mallorca Island, Spain). A third site, Alborán (Alborán Island, Spain), with only a few months of data is considered for examining possible northeast-southwest (NE-SW) gradients of the aforementioned aerosol properties. The AERONET dataset is exclusively composed of level 2.0 inversion products available during the 5-year period 2011-2015. AERONET solar radiative fluxes are compared with groundand satellite-based flux measurements. To the best of our knowledge this is the first time that AERONET fluxes are compared with measurements at the top of the atmosphere. Strong events (with an aerosol optical depth at 440 nm greater than 0.4) of long-range transport aerosols, one of the main drivers of the observed annual cycles and NE-SW gradients, are (1) mineral dust outbreaks predominant in spring and summer in the north and in summer in the south and (2) European pollution episodes predominant in autumn. A NE-SW gradient exists in the western Mediterranean Basin for the aerosol optical depth and especially its coarse-mode fraction, which all together produces a similar gradient for the aerosol direct radiative forcing. The aerosol fine mode is rather homogeneously distributed. Absorption properties are quite variable because of the many and different sources of anthropogenic particles in and around the western Mediterranean Basin: North African and European urban areas, the Iberian and Italian peninsulas, most forest fires and ship emissions. As a result, the aerosol direct forcing efficiency, more dependent to absorption than the absolute forcing, has no marked gradient. © Author(s) 2016.


Mandija F.,University of Shkodra | Mandija F.,Andalusian Institute for Earth System Research IISTA CEAMA | Guerrero-Rascado J.L.,Andalusian Institute for Earth System Research IISTA CEAMA | Guerrero-Rascado J.L.,University of Granada | And 6 more authors.
Atmospheric Environment | Year: 2016

In this paper, we present a study of the columnar and vertically resolved aerosol optical properties over Granada (Spain) during dust events detected during July-August in the period 2012–2013. For this purpose, we classified the events according to their origins and pathways. The analyzed aerosol properties include; columnar aerosol optical properties like aerosol optical depth (AOD) and Angstrom exponent (AE), as well as the lidar products, like backscatter-related Angstrom exponent and linear particle depolarization ratio (LDPR). The lidar profiles are used for determination of the geometrical structure of dust layers and the aerosol optical parameters inside dust layers. There are identified 58 dusty days over Granada during the periods July-August, 2012–2013. In 71% of the dust, event analyzed the dust plume over Granada is located between 3000 and 4000 m a.g.l. Mean values of AOD500 according to the Atlantic and Mediterranean pathway were 0.28 ± 0.10 and 0.93 ± 0.17. Meanwhile, the mean values of AE440-870 were 0.57 ± 0.25 and 0.43 ± 0.20. Three region are identified as the main dust sources affecting the dust intrusions over Granada. Two principal pathways of air masses during dust intrusion over Granada were observed: through Atlantic (52.7%) and through Mediterranean (47.3%). Air masses which come through the Mediterranean present larger AOD and lower Angstrom exponent values than those air masses coming through Atlantic. Lidar measurements show different vertical distributions on particle backscatter coefficient, during different scenarios of dust intrusions. The lidar profiles indicate that average base and top heights of all dust during the investigation period were 2.1 ± 0.7 and 4.8 ± 0.9 km, and their center of mass and thickness were 3.3 ± 0.7 and 2.8 ± 1.0 km a.g.l. The AE355/532 profiles for the dust intrusions present some differences depending on the source regions and path followed by the dust. On the other hand, the profiles of LPDRat 532 nm were more similar for all scenarios. © 2016 Elsevier Ltd


Antonio Bravo-Aranda J.,Andalusian Institute for Earth System Research IISTA CEAMA | Antonio Bravo-Aranda J.,University of Granada | Antonio Bravo-Aranda J.,Ecole Polytechnique - Palaiseau | Belegante L.,Romanian National Institute for Optoelectronics | And 23 more authors.
Atmospheric Measurement Techniques | Year: 2016

Lidar depolarization measurements distinguish between spherical and non-spherical aerosol particles based on the change of the polarization state between the emitted and received signal. The particle shape information in combination with other aerosol optical properties allows the characterization of different aerosol types and the retrieval of aerosol particle microphysical properties. Regarding the microphysical inversions, the lidar depolarization technique is becoming a key method since particle shape information can be used by algorithms based on spheres and spheroids, optimizing the retrieval procedure. Thus, the identification of the depolarization error sources and the quantification of their effects are crucial. This work presents a new tool to assess the systematic error of the volume linear depolarization ratio (δ), combining the Stokes-Müller formalism and the complete sampling of the error space using the lidar model presented in Freudenthaler (2016a). This tool is applied to a synthetic lidar system and to several EARLINET lidars with depolarization capabilities at 355 or 532 nm. The lidar systems show relative errors of δ larger than 100% for δ values around molecular linear depolarization ratios (∼ 0.004 and up to ∼ 10 % for δ = 0.45). However, one system shows only relative errors of 25 and 0.22% for δ = 0.004 and δ = 0.45, respectively, and gives an example of how a proper identification and reduction of the main error sources can drastically reduce the systematic errors of δ. In this regard, we provide some indications of how to reduce the systematic errors. © 2016 The Author(s).


Lyamani H.,Andalusian Institute for Earth System Research IISTA CEAMA | Lyamani H.,University of Granada | Valenzuela A.,Andalusian Institute for Earth System Research IISTA CEAMA | Valenzuela A.,University of Granada | And 9 more authors.
Atmospheric Chemistry and Physics | Year: 2015

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. © Author(s) 2015.


Granados-Munoz M.J.,University of Granada | Granados-Munoz M.J.,Andalusian Institute for Earth System Research IISTA CEAMA | Navas-Guzman F.,University of Granada | Navas-Guzman F.,Andalusian Institute for Earth System Research IISTA CEAMA | And 15 more authors.
Atmospheric Measurement Techniques | Year: 2015

A new methodology based on combining active and passive remote sensing and simultaneous and collocated radiosounding data to study the aerosol hygroscopic growth effects on the particle optical and microphysical properties is presented. The identification of hygroscopic growth situations combines the analysis of multispectral aerosol particle backscatter coefficient and particle linear depolarization ratio with thermodynamic profiling of the atmospheric column. We analyzed the hygroscopic growth effects on aerosol properties, namely the aerosol particle backscatter coefficient and the volume concentration profiles, using data gathered at Granada EARLINET station. Two study cases, corresponding to different aerosol loads and different aerosol types, are used for illustrating the potential of this methodology. Values of the aerosol particle backscatter coefficient enhancement factors range from 2.1 ± 0.8 to 3.9 ± 1.5, in the ranges of relative humidity 60-90 and 40-83%, being similar to those previously reported in the literature. Differences in the enhancement factor are directly linked to the composition of the atmospheric aerosol. The largest value of the aerosol particle backscatter coefficient enhancement factor corresponds to the presence of sulphate and marine particles that are more affected by hygroscopic growth. On the contrary, the lowest value of the enhancement factor corresponds to an aerosol mixture containing sulphates and slight traces of mineral dust. The Hänel parameterization is applied to these case studies, obtaining results within the range of values reported in previous studies, with values of the γ exponent of 0.56 ± 0.01 (for anthropogenic particles slightly influenced by mineral dust) and 1.07 ± 0.01 (for the situation dominated by anthropogenic particles), showing the convenience of this remote sensing approach for the study of hygroscopic effects of the atmospheric aerosol under ambient unperturbed conditions. For the first time, the retrieval of the volume concentration profiles for these cases using the Lidar Radiometer Inversion Code (LIRIC) allows us to analyze the aerosol hygroscopic growth effects on aerosol volume concentration, observing a stronger increase of the fine mode volume concentration with increasing relative humidity. © Author(s) 2015.


Granados-Munoz M.J.,University of Granada | Granados-Munoz M.J.,Andalusian Institute for Earth System Research IISTA CEAMA | Guerrero-Rascado J.L.,University of Granada | Guerrero-Rascado J.L.,Andalusian Institute for Earth System Research IISTA CEAMA | And 16 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2014

LIRIC (Lidar-Radiometer Inversion Code) is applied to combined lidar and Sun photometer data from Granada station corresponding to different case studies. The main aim of this analysis is to evaluate the stability of LIRIC output volume concentration profiles for different aerosol types, loadings, and vertical distributions of the atmospheric aerosols. For this purpose, in a first part, three case studies corresponding to different atmospheric situations are analyzed to study the influence of the user-defined input parameters in LIRIC when varied in a reasonable range. Results evidence the capabilities of LIRIC to retrieve vertical profiles of microphysical properties during daytime by the combination of the lidar and the Sun photometer systems in an automatic and self-consistent way. However, spurious values may be obtained in the lidar incomplete overlap region depending on the structure of the aerosol layers. In a second part, the use of a second Sun photometer located in Cerro Poyos, in the same atmospheric column as Granada but at higher altitude, allowed us to obtain LIRIC retrievals from two different altitudes with independent Sun photometer measurements in order to check the self-consistency and robustness of the method. Retrievals at both levels are compared, providing a very good agreement (differences below 5-μm3/cm3) in those cases with the same aerosol type in the whole atmospheric column. However, some assumptions such as the height independency of parameters (sphericity, size distribution, or refractive index, among others) need to be carefully reviewed for those cases with the presence of aerosol layers corresponding to different types of atmospheric aerosols. Key Points Microphysical properties are retrieved with LIRIC from lidar and Sun photometer Uncertainties of LIRIC algorithm are evaluated for different conditions A unique set up with two Sun photometers at two altitude levels is used. © 2014. American Geophysical Union. All Rights Reserved.


Nepomuceno Pereira S.,Evora Geophysics Center | Nepomuceno Pereira S.,Andalusian Institute for Earth System Research IISTA CEAMA | Wagner F.,Evora Geophysics Center | Wagner F.,Hohenpeissenberg Meteorological Observatory | Silva A.M.,Evora Geophysics Center
Advances in Meteorology | Year: 2014

Measurements of the aerosol absorption coefficient, between 2007 and 2013, were made at the ground level in Évora, a Portuguese small town located in the southwestern Iberia Peninsula. Such a relatively long time series of absorbing aerosols is unique in Portugal and uncommon elsewhere. The average aerosol absorption coefficient was close to 9 Mm-1 and clear cycles at both daily and seasonal time scales were found. An average increase by a factor of two (from 6 to 12 Mm-1) was observed in winter if compared to summer season. The daily variations were similarly shaped for all seasons, with two morning and afternoon peaks, but with magnitudes modulated by the seasonal evolution. That was not the case if Sundays were considered. These variations can be explained in terms of the impact of local particle sources, related mainly to traffic and biomass burning and upward mixing of the aerosol due to variable mixing layer heights, either daily or seasonally. Also, a strong negative correlation between the aerosol absorption coefficient and the wind speed was verified, and an exponential decay function was found to fit very well to the data. The wind direction seems to be not correlated with the aerosol absorption coefficient. © 2014 Sérgio Nepomuceno Pereira et al.

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