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

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. Source

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

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. Source

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

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. Source

Granados-Munoz M.J.,Andalusian Institute for Earth System Research IISTA CEAMA | Granados-Munoz M.J.,University of Granada | Granados-Munoz M.J.,Jet Propulsion Laboratory | Bravo-Aranda J.A.,Andalusian Institute for Earth System Research IISTA CEAMA | And 23 more authors.
Atmospheric Measurement Techniques

In this work we present an analysis of aerosol microphysical properties during a mineral dust event taking advantage of the combination of different state-of-the-art retrieval techniques applied to active and passive remote sensing measurements and the evaluation of some of those techniques using independent data acquired from in situ aircraft measurements. Data were collected in a field campaign performed during a mineral dust outbreak at the Granada, Spain, experimental site (37.16° N, 3.61° W, 680 m a.s.l.) on 27 June 2011. Column-integrated properties are provided by sun- and star-photometry, which allows for a continuous evaluation of the mineral dust optical properties during both day and nighttime. Both the linear estimation and AERONET (Aerosol Robotic Network) inversion algorithms are applied for the retrieval of the column-integrated microphysical particle properties. In addition, vertically resolved microphysical properties are obtained from a multi-wavelength Raman lidar system included in EARLINET (European Aerosol Research Lidar Network), by using both LIRIC (Lidar Radiometer Inversion Code) algorithm during daytime and an algorithm applied to the Raman measurements based on the regularization technique during nighttime. LIRIC retrievals reveal the presence of dust layers between 3 and 5 km a.s.l. with volume concentrations of the coarse spheroid mode up to 60 μm3 cm-3. The combined use of the regularization and LIRIC methods reveals the night-to-day evolution of the vertical structure of the mineral dust microphysical properties and offers complementary information to that from column-integrated variables retrieved from passive remote sensing. Additionally, lidar depolarization profiles and LIRIC retrieved volume concentration are compared with aircraft in situ measurements. This study presents for the first time a comparison of the total volume concentration retrieved with LIRIC with independent in situ measurements, obtaining agreement within the estimated uncertainties for both methods and quite good agreement for the vertical distribution of the aerosol layers. Regarding the depolarization, the first published data set of the CAS-POL for polarization ratios is presented here and qualitatively compared with the lidar technique. © Author(s) 2016. Source

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

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. Source

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