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An overview of sun photometer measurements of aerosol properties in Scandinavia and Svalbard was provided by Toledano et al. (2012) thanks to the collaborative effort of various research groups from different countries that maintain a number of observation sites in the European Arctic and sub-Arctic regions. The spatial coverage of this kind of data has remarkably improved in the last years, thanks, among other things, to projects carried out within the framework of the International Polar Year 2007-08. The data from a set of operational sun photometer sites belonging either to national or international measurement networks (AERONET, GAW-PFR) were evaluated. The direct sun observations provided spectral aerosol optical depth (AOD) and Ångstro¨m exponent (AE), that are parameters with sufficient long-term records for a first characterization at all sites. At the AERONET sites, microphysical properties derived from inversion of sun-sky radiance data were also examined. AOD (500nm) ranged from 0.08 to 0.10 in Arctic and sub-Arctic sites whereas the aerosol load was higher in more populated areas in Southern Scandinavia (average AOD about 0.10-0.12 at 500 nm). On the Norwegian coast, aerosols showed larger mean size than in continental areas. Columnar particle size distributions and related parameters were used to evaluate aerosol volume efficiencies. The aerosol optical depth characterization revealed that the seasonal patterns in the high Arctic (with the typical hazy spring), in the sub-Arctic region and Southern Scandinavia are all different. The clean continental, polluted continental and maritime aerosols constitute the three main aerosol types, although persistent (Asian) dust was also detected in Svalbard. [ABSTRACT FROM AUTHOR]

Remote sensing of the atmospheric aerosol is a well-established technique that is currently used for routine monitoring of this atmospheric component, both from ground-based and satellite. The AERONET program, initiated in the 90's, is the most extended network and the data provided are currently used by a wide community of users for aerosol characterization, satellite and model validation and synergetic use with other instrumentation (lidar, in-situ, etc.). Aerosol properties are derived within the network from measurements made by ground-based Sun-sky scanning radiometers. Sky radiances are acquired in two geometries: almucantar and principal plane. Discrepancies in the products obtained following both geometries have been observed and the main aim of this work is to determine if they could be justified by measurement errors. Three systematic errors have been analyzed in order to quantify the effects on the inversion-derived aerosol properties: calibration, pointing accuracy and finite field of view. Simulations have shown that typical uncertainty in the analyzed quantities (5% in calibration, 0.2° in pointing and 1.2° field of view) yields to errors in the retrieved parameters that vary depending on the aerosol type and geometry. While calibration and pointing errors have relevant impact on the products, the finite field of view does not produce notable differences. [ABSTRACT FROM AUTHOR]

A field campaign of the Saharan Mineral Dust Experiment (SAMUM-2) took place in the Cape Verde islands in January-February 2008, to investigate the properties of long-range transported dust over the Atlantic. The Meteorological Institute of the University of Munich deployed a set of active and passive remote sensing instruments: one sun photometer, for the measurement of the direct sun irradiance and sky radiances; a broad-band UV radiometer; and 2 tropospheric lidar systems. The measurements were made in close cooperation with the other participating groups. During the measurement period the aerosol scenario over Cape Verde mostly consisted of a dust layer below 2 km and a smoke layer above 2 km height. The Saharan dust arrived in the site from the NE, whereas the smoke originated in the African equatorial region is transported from the SE. The aerosol load was also very variable over this area, with AOD (500 nm) ranging from 0.04 to 0.74. The optical properties of the layers are shown: extinction and particle depolarization ratio profiles at 3 wavelengths, as well as aerosol optical depth (in the range 340–1550 nm), Ångström exponent, size distribution and single scattering albedo. [ABSTRACT FROM AUTHOR]

The present work shows the main results of the analysis of AERONET inversion algorithm’s products of a sun-photometer installed at the Atmospheric Sounding Station “El Arenosillo.” This station belongs to INTA (Instituto Nacional de Técnica Aerosoespacial) and is located in the southwest of the Iberian Peninsula (37.1 N—6.7 W). The aim of this work is the study of the optical aerosol properties of a long data series (August 2002–December 2005) that are products of the AERONET inversion algorithm: volume size distribution (VSD) and complex refractive index (REF), and a wide set of derived parameters: volume concentration (VolCon), asymmetry parameter (g), single scattering albedo (SSA), etc. Version 2 of the AERONET algorithm inversion is used here. A general statistic is carried out which includes the interannual monthly behaviour of the aerosol microphysical parameters. Aerosol volume concentration shows a good correlation with the aerosol optical depth (AOD) and also the fine mode volume fraction (Vf/Vt) with the alpha Ångström exponent (AE). A characterization of the VSD and derived parameters is performed depending on aerosol type. Optical properties will be analyzed only for cases of high AOD, because of the quality assured criteria of these parameters. These cases include desert dust, showing a scattering behaviour, and biomass burning aerosol, with an absorbing character. [ABSTRACT FROM AUTHOR]

The Atmospheric Optics Group (GOA-UVA) at the University of Valladolid has carried out seven field campaigns to investigate Sub-Arctic aerosols. The measurements have been made between 2002 and 2007 at the Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR), Ando\ya Rocket Range, Norway (69 N, 16 E, elev. 380 m) in order to investigate the main characteristics of the columnar aerosol properties in this area. Different sun photometers and spectroradiometers have been used for this purpose. The main systems have been sun photometer from Cimel. From the measurements we can retrieve the aerosol optical depth (AOD) and the derived Ångström exponent (alpha) and provide information on pollution and Arctic haze events in the region. The optical properties are analyzed jointly with air mass back trajectories in order to investigate the prevailing aerosol types and determine the origin of the aerosols. Routine measurements carried out since 2006, in collaboration with NILU and ALOMAR, will provide better statistic and will lead to an improved characterization of Sub-Arctic aerosols in the near future. [ABSTRACT FROM AUTHOR]