Abstract.A global vertically resolved aerosol data set covering more than 10 years of observations at more than 20 measurement sites distributed from 63 • N to 52 • S and 72 • W to 124 • E has been achieved within the Raman and polarization lidar network Polly NET . This network consists of portable, remote-controlled multiwavelength-polarization-Raman lidars (Polly) for automated and continuous 24/7 observations of clouds and aerosols. Polly NET is an independent, voluntary, and scientific network. All Polly lidars feature a standardized instrument design with different capabilities ranging from single wavelength to multiwavelength systems, and now apply unified calibration, quality control, and data analysis. The observations are processed in near-real time without manual intervention, and are presented online at polly.tropos.de. The paper gives an overview of the observations on four continents and two research vessels obtained with eight Polly systems. The specific aerosol types at these locations (mineral dust, smoke, dust-smoke and other dusty mixtures, urban haze, and volcanic ash) are identified by their Ångström exponent, lidar ratio, and depolarization ratio. The vertical aerosol distribution at the Polly NET locations is discussed on the basis of more than 55 000 automatically retrieved 30 min particle backscatter coefficient profiles at 532 nm as this operating wavelength is available for all Polly lidar systems. A seasonal analysis of measurements at selected sites revealed typical and extraordinary aerosol conditions as well as seasonal differences. These studies show the potential of Polly NET to support the establishment of a global aerosol climatology that covers the entire troposphere.

Published by Copernicus Publications on behalf of the European Geosciences Union. I. Binietoglou et al.: Dust model comparison methodologyAbstract. Systematic measurements of dust concentration profiles at a continental scale were recently made possible by the development of synergistic retrieval algorithms using combined lidar and sun photometer data and the establishment of robust remote-sensing networks in the framework of Aerosols, Clouds, and Trace gases Research InfraStructure Network (ACTRIS)/European Aerosol Research Lidar Network (EARLINET). We present a methodology for using these capabilities as a tool for examining the performance of dust transport models. The methodology includes considerations for the selection of a suitable data set and appropriate metrics for the exploration of the results. The approach is demonstrated for four regional dust transport models (BSC-DREAM8b v2, NMMB/BSC-DUST, DREAM-ABOL, DREAM8-NMME-MACC) using dust observations performed at 10 ACTRIS/EARLINET stations. The observations, which include coincident multi-wavelength lidar and sun photometer measurements, were processed with the Lidar-Radiometer Inversion Code (LIRIC) to retrieve aerosol concentration profiles. The methodology proposed here shows advantages when compared to traditional evaluation techniques that utilize separately the available measurements such as separating the contribution of dust from other aerosol types on the lidar profiles and avoiding model assumptions related to the conversion of concentration fields to aerosol extinction values. When compared to LIRIC retrievals, the simulated dust vertical structures were found to be in good agreement for all models with correlation values between 0.5 and 0.7 in the 1-6 km range, where most dust is typically observed. The absolute dust concentration was typically underestimated with mean bias values of −40 to −20 µg m −3 at 2 km, the altitude of maximum mean concentration. The reported differences among the models found in this comparison indicate the benefit of the systematic use of the proposed approach in future dust model evaluation studies.

Abstract. The CALIPSO Level 3 (CL3) product is the most recent data set produced by the observations of the CloudAerosol Lidar with Orthogonal Polarization (CALIOP) instrument onboard the Cloud-Aerosol Lidar and Pathfinder Satellite Observations (CALIPSO) space platform. The European Aerosol Research Lidar Network (EARLINET), based mainly on multi-wavelength Raman lidar systems, is the most appropriate ground-based reference for CALIPSO calibration/validation studies on a continental scale. In this work, CALIPSO data are compared against EARLINET monthly averaged profiles obtained by measurements performed during CALIPSO overpasses. In order to mitigate uncertainties due to spatial and temporal differences, we reproduce a modified version of CL3 data starting from CALIPSO Level 2 (CL2) data. The spatial resolution is finer and nearly 2 • × 2 • (latitude × longitude) and only simultaneous measurements are used for ease of comparison. The CALIPSO monthly mean profiles following this approach are called CALIPSO Level 3 * , CL3 * . We find good agreement on the aerosol extinction coefficient, yet in most of the cases a small CALIPSO underestimation is observed with an average bias of 0.02 km −1 up to 4 km and 0.003 km −1 higher above. In contrast to CL3 standard product, the CL3 * data set offers the possibility to assess the CALIPSO performance also in terms of the particle backscatter coefficient keeping the same quality assurance criteria applied to extinction profiles. The mean relative difference in the comparison improved from 25 % for extinction to 18 % for backscatter, showing better performances of CALIPSO backscatter retrievals. Additionally, the aerosol typing comparison yielded a robust identification of dust and polluted dust. Moreover, the CALIPSO aerosol-type-dependent lidar ratio selection is assessed by means of EARLINET observations, so as to investigate the performance of the extinction retrievals. The aerosol types of dust, polluted dust, and clean continental showed noticeable discrepancy. Finally, the potential improvements of the lidar ratio assignment have been examined by adjusting it according to EARLINET-derived values.

[1] Summer in É vora (38°34 0 N, 7°54 0 W), Portugal, is described in terms of aerosol properties of extinction of the solar radiation. We create a data set composed of (1) cloudscreened half-day averaged values of aerosol optical thickness (AOT) measured at 7 wavelengths by both a CIMEL Sun/sky-photometer and a YES shadowband radiometer and (2) half day averaged values of aerosol scattering coefficient (ASC) measured at the surface level at two wavelengths by a TSI nephelometer. Spectral dependence of both AOT and ASC gives the column and the surface Å ngström exponents, a C and a S , respectively. Measurements are acquired in both 2002 and 2003 summers. Back trajectories are computed. A statistical study of the data set provides thresholds in AOT and a C for a classification of the days. The classification is applied with success to the case study of the 2003 summer heat wave episode and is generalized to the whole data set. In 23% of the cases, the turbidity in É vora is very low, with AOT441 < 0.12 and AOT873 < 0.04. The air mass origin is the North Atlantic Ocean at 700 and 970 hPa. In 31% of the cases, the turbidity is high. Increase of AOT is due to forest fire emissions, originating in the Iberian Peninsula, with 0.30 < AOT441 < 1.10 and a C > 1.2, and to desert dust plumes transported from North Africa within 72 to 120 hours at 700 hPa, with 0.10 < AOT873 < 1.10 and 0.1 < a C < 1.0. The vertical profile is highly variable, and several cases of aerosol mixing in the column are identified. The duration of the aerosol episode during the 2003 summer heat wave is 16 days, which is exceptionally long.

Abstract. Aerosol scattering properties, near the surface (at about 10 m height), were measured during a period of seven years (2002)(2003)(2004)(2005)(2006)(2007)(2008) atÉvora, Portugal. The average (and median) scattering and backscattering coefficients, at the wavelength of 550 nm, were found to be 42.5 Mm −1 (29.9 Mm −1 ) and 5.9 Mm −1 (4.4 Mm −1 ), respectively. Also, the average and median scatteringÅngström exponent (1.4 and 1.5) indicate that scattering was, in general, dominated by submicrometer particles. Both seasonal and daily cycles are shown, which were related to local production and transport of particles from elsewhere. Summer and winter average values of the scattering coefficient, at the wavelength of 550 nm (47 and 54 Mm −1 , respectively), correspond to a significant increase in the aerosol particle concentration when compared with spring and fall (35 and 37 Mm −1 , respectively). Also, the average increase in theÅngström exponent for summer and winter seasons is consistent with the input of sub-micrometer particles from anthropogenic origin in winter and forest fires in summer.Back-trajectory analysis indicated that the site was regularly under the influence of air masses from the Atlantic area, with low particle loads (low scattering coefficients), but as the influence of transport from the continent (Iberia Peninsula) increased, the aerosol particle load was observed to increase as well as the relative importance of fine particles over coarse ones, approaching the features observed at the site during European air masses influence.