Suchergebnisse

A sensitivity study of aerosol retrievals to the geometrical configuration of the ground-based sky radiometer observations is carried out through inversion tests. Specifically, this study is focused on principal plane and almucantar observations, since these geometries are employed in AERONET (AErosol RObotic NETwork). The following effects have been analyzed with simulated data for both geometries: sensitivity of the retrieval to variability of the observed scattering angle range, uncertainties in the assumptions of the aerosol vertical distribution, surface reflectance, possible instrument pointing errors, and the effects of the finite field of view. ; Financial support was provided by the Spanish CICYT (CGL2009-09740 and CGL2011-23413, CGL2011-13085-E). The research leading to these results was supported by funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 262254 [ACTRIS]. We also thank the Environmental Council of the CyL Regional Government (Consejería de Medio Ambiente, Junta de Castilla y León) for supporting this research.

A sensitivity study of aerosol retrievals to the geometrical configuration of the ground-based sky radiometer observations is carried out through inversion tests. Specifically, this study is focused on principal plane and almucantar observations, since these geometries are employed in AERONET (AErosol RObotic NETwork). The following effects have been analyzed with simulated data for both geometries: sensitivity of the retrieval to variability of the observed scattering angle range, uncertainties in the assumptions of the aerosol vertical distribution, surface reflectance, possible instrument pointing errors, and the effects of the finite field of view. ; Financial support was provided by the Spanish CICYT (CGL2009-09740 and CGL2011-23413, CGL2011-13085-E). The research leading to these results was supported by funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 262254 [ACTRIS]. We also thank the Environmental Council of the CyL Regional Government (Consejería de Medio Ambiente, Junta de Castilla y León) for supporting this research.

Comunicación presentada en: 2012 European Aerosol Conference (EAC-2012), B-WG01S2P30, celebrada del 2 al 7 de septiembre de 2012 en Granada. ; Financial supports from the Spanish MICIIN (projects of ref. CGL2008-05939-CO3-01/CLI, CGL 2009-09740, and "Acción Complementaria" CGL2010-09480-E and CGL2011-13085-E), and from the Environmental Council of the CyL Regional Government (Consejería de Medio Ambiente, Junta de Castilla y León) are gratefully acknowledged.

Producción Científica ; The relationship between columnar and surface aerosol properties is not a straightforward problem. The Aerosol Optical Depth (AOD), Ångström exponent (AE), and ground-level Particulate Matter (PMX, x=10 or 2.5 µm) data have been studied from a climatological point of view. Despite the different meanings of AOD and PMx both are key and complementary quantities that quantify aerosol load in the atmosphere and many studies intend to find specific relationships between them. Related parameters such as AE and PM ratio (PR=PM2.5/ PM10), giving information about the predominant particle size, are included in this study on the relationships between columnar and surface aerosol parameters. This study is based on long measurement records (2003–2014) obtained at two nearby background sites from the AERONET and EMEP networks in the north-central area of Spain. The climatological annual cycle of PMx shows two maxima along the year (one in late-winter/early-spring and another in summer), but this cycle is not followed by the AOD which shows only a summer maximum and a nearly bell shape. However, the annual means of both data sets show strong correlation (R=0.89) and similar decreasing trends of 40% (PM10) and 38% (AOD) for the 12-year record. PM10 and AOD daily data are moderately correlated (R=0.58), whereas correlation increases for monthly (R=0.74) and yearly (R=0.89) means. Scatter plots of AE vs. AOD and PR vs. PM10 have been used to characterize aerosols over the region. The PR vs. AE scatterplot of daily data shows no correlation due to the prevalence of intermediate-sized particles. As day-to-day correlation is low (especially for high turbidity events), a binned analysis was also carried out to establish consistent relationships between columnar and surface quantities, which is considered to be an appropriate approach for environmental and climate studies. In this way the link between surface concentrations and columnar remote sensing data is shown to provide useful information for aerosol characterization from a climatological context, despite some limitations. ; Thanks to MINECO for the financial support of the FPI grant BES-2012-051868; "Juan de la Cierva - Incorporación" grant IJCI-2014-19477 and project CMT2015-66742-R. We also thaks to the Environmental Council of the CyL Regional Government ("Consejería de Medio Ambiente, Junta de Castilla y León") for supporting this research about atmospheric aerosols as well as Consejería de Educación for supporting the project VA100U14.

This study evaluates the potential of using aerosol optical depth (τa) measurements to characterize the microphysical and optical properties of atmospheric aerosols. With this aim, we used the recently developed GRASP (Generalized Retrieval of Aerosol and Surface Properties) code for numerical testing of six different aerosol models with three different aerosol loads. We found that bimodal log-normal size distributions serve as useful input assumptions, especially when the measurements have inadequate spectral coverage and/or limited accuracy, such as lunar photometry. The direct numerical simulations indicate that the GRASP-AOD retrieval provides modal aerosol optical depths (fine and coarse) to within 0.01 of the input values. The retrieval of the fine mode radius, width, and volume concentration is stable and precise if the real part of the refractive index is known (.) ; The research has been supported by the Labex CaPPA: the CaPPA project (Chemical and Physical Properties of the Atmosphere) is funded by the French National Research Agency (ANR) through the PIA (Programme d'Investissement d'Avenir) under contract "ANR-11-LABX-0005-01" and by the Regional Council "Nord Pas de Calais - Picardie" and the European Funds for Regional Economic Development (FEDER). This research has also received funding from the French National Research Agency (ANR) project ADRIMED (contract ANR-11-BS56- 0006). The authors acknowledge the funding provided by the European Union (H2020-INFRAIA-2014-2015) under Grant Agreement No. 654109 (ACTRIS-2). Financial support was also provided by MINECO (CTM2015-66742-R).

We report the results of Sub-Arctic aerosol properties, obtained during three field campaigns conducted in 2005 and 2006. These have been carried out at the Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR), Andøya Rocket Range, Norway (69N, 16E, 380 m asl), and were supported by the eARI (enhanced Access to Research Infrastructure) program of the European Union. The instruments used for this study are the ALOMAR tropospheric Lidar and a Cimel sun photometer. Data in situ from cascade impactors are also included to know the levels of total suspended particles and major ionic components during the measurement period in 2005. Back trajectory analysis is presented. The evolution of the vertical distribution of the aerosols is analyzed, in order to study aerosol stratification and height patterns for the long-range transported aerosols to this coastal Sub-Arctic site. ; info:eu-repo/semantics/publishedVersion

Sensitivity studies indicate that among the diverse error sources of ground-based sky radiometer observations, the pointing error plays an important role in the correct retrieval of aerosol properties. The accurate pointing is specially critical for the characterization of desert dust aerosol. The present work relies on the analysis of two new measurement procedures (cross and matrix) specifically designed for the evaluation of the pointing error in the standard instrument of the Aerosol Robotic Network (AERONET), the Cimel CE-318 Sun photometer. The first part of the analysis contains a preliminary study whose results conclude on the need of a Sun movement correction for an accurate evaluation of the pointing error from both new measurements. ; We thank the AERONET, PHOTONS, RIMA and WRC staff for their scientifc and technical support. Financial support was provided by: the Spanish CICYT (CGL2009- 09740 and CGL2011-23413, CGL2011-13085-E). The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007–2013) under grant agreement Nr. 262254 [ACTRIS].

Sensitivity studies indicate that among the diverse error sources of ground-based sky radiometer observations, the pointing error plays an important role in the correct retrieval of aerosol properties. The accurate pointing is specially critical for the characterization of desert dust aerosol. The present work relies on the analysis of two new measurement procedures (cross and matrix) specifically designed for the evaluation of the pointing error in the standard instrument of the Aerosol Robotic Network (AERONET), the Cimel CE-318 Sun photometer. The first part of the analysis contains a preliminary study whose results conclude on the need of a Sun movement correction for an accurate evaluation of the pointing error from both new measurements. Once this correction is applied, both measurements show equivalent results with differences under 0.01° in the pointing error estimations. The second part of the analysis includes the incorporation of the cross procedure in the AERONET routine measurement protocol in order to monitor the pointing error in field instruments. The pointing error was evaluated using the data collected for more than a year, in 7 Sun photometers belonging to AERONET sites. ; We thank the AERONET, PHOTONS, RIMA and WRC staff for their scientific and technical support. Financial support was provided by the Spanish CICYT (CGL2009-09740 and CGL2011-23413, CGL2011-13085-E). The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 262254 [ACTRIS].

The use of sky cameras for nocturnal aerosol characterization is discussed in this study. Two sky cameras are configured to take High Dynamic Range (HDR) images at Granada and Valladolid (Spain). Some properties of the cameras, like effective wavelengths, sky coordinates of each pixel and pixel sensitivity, are characterized. After that, normalized camera radiances at lunar almucantar points (up to 20° in azimuth from the Moon) are obtained at three effective wavelengths from the HDR images. These normalized radiances are compared in different case studies to simulations fed with AERONET aerosol information, giving satisfactory results. The obtained uncertainty of normalized camera radiances is around 10% at 533 nm and 608 nm and 14% for 469 nm. Normalized camera radiances and six spectral aerosol optical depth values (obtained from lunar photometry) are used as input in GRASP code (Generalized Retrieval of Aerosol and Surface Properties) to retrieve aerosol properties for a dust episode over Valladolid. The retrieved aerosol properties (refractive indices, fraction of spherical particles and size distribution parameters) are in agreement with the nearest diurnal AERONET products. The calculated GRASP retrieval at night time shows an increase in coarse mode concentration along the night, while fine mode properties remained constant. ; This work was supported by the Andalusia Regional Government(project P12-RNM-2409) and by the"Consejería de Educación, Juntade Castilla y León"(project VA100U14); the Spanish Ministry of Econo-my and Competitiveness and FEDER funds under the projects CGL2013-45410-R, CMT2015-66742-R, CGL2016-81092-R and"Juan de la Cierva Formación"program (FJCI-2014-22052); and the European Union's Ho-rizon 2020 research and innovation programme through projectACTRIS-2 (grant agreement No 654109).