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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]

The aerosol optical depth (AOD) very often shows a distinct diurnal cycle pattern, which results to be an artifact arising from an incorrect calibration (or an equivalent effect, as filter degradation). The shape of this fictitious AOD diurnal cycle varies as the solar air mass (or the solar zenith angle, SZA) and the magnitude of the effect is largest at noon. The observation of this effect is not easy at many field stations and only those stations with good weather conditions permit an easier detection and the possibility of its correction. By taking advantage of this dependence on the SZA, we propose an “in situ” correction-calibration procedure for AOD data series. The method is named KCICLO because it is based on the determination of a constant K and the behavior of AOD as a cycle (ciclo, in Spanish). We estimate that the KCICLO method has an accuracy of 0.2–0.5% for the calibration ratio constant K, or 0.002–0.005 in AOD at field stations. The application of this calibration correction method to the five years AOD data series at El Arenosillo site (southwestern Spain)—belonging to the AERONET-PHOTONS network—has been carried out, and the results show that 9 of the 16 channels of the four analyzed sun photometers were outside the 0.02 uncertainty specified by AERONET. The largest departures reached values of 0.06 in AOD. The results show the effectiveness of the method and a significant improvement over other “in situ” methods, with no other information required except the AOD data themselves. Also an extensive comparison between the corrected data with the KCICLO method and the AERONET data base is carried out. These comparative results give a representative pattern of the uncertainties that we have found in establishing a local aerosol climatology. [ABSTRACT FROM AUTHOR]