Nabro volcano (13.37 • N, 41.70 • E) in Eritrea erupted on 13 June 2011 generating a layer of sulfate aerosols that persisted in the stratosphere for months. For the first time we report on ground-based lidar observations of the same event from every continent in the Northern Hemisphere, taking advantage of the synergy between global lidar networks such as EARLINET, MPLNET and NDACC with independent lidar groups and satellite CALIPSO to track the evolution of the stratospheric aerosol layer in various parts of the globe. The globally averaged aerosol optical depth (AOD) due to the stratospheric volcanic aerosol layers was of the order of 0.018±0.009 at 532 nm, ranging from 0.003 to 0.04. Compared to the total column AOD from the available collocated AERONET stations, the stratospheric contribution varied from 2% to 23% at 532 nm.

Six months of stratospheric aerosol observations with the European Aerosol Research Lidar Network (EAR-LINET)

Abstract. The synergetic use of meteorological information, remote sensing both ground-based active (lidar) and passive (sun-photometry) techniques together with backtrajectory analysis and in-situ measurements is devoted to the characterization of dust intrusions. A case study of air masses advected from the Saharan region to the Canary Islands and the Iberian Peninsula, located relatively close and far away from the dust sources, respectively, was considered for this purpose. The observations were performed over three Spanish geographically strategic stations within the dust-influenced area along a common dust plume pathway monitored from 11 to 19 of March 2008. A 4-day long dust event (13-16 March) over the Santa Cruz de Tenerife Observatory (SCO), and a linked short 1-day dust episode (14 March) in the Southern Iberian Peninsula over the Atmospheric Sounding Station "El Arenosillo" (ARN) and the Granada station (GRA) were detected. Meteorological conditions favoured the dust plume transport over the area under study. Backtrajectory analysis clearly revealed the Saharan region as the source of the dust intrusion. Under the Saharan air masses influence, AERONET Aerosol Optical Depth at 500 nm (AOD 500 ) ranged from 0.3 to 0.6 andÅngström Exponent at 440/675 nm wavelength pair (AE 440/675 ) was lower than 0.5, indicating a high loading and predominanceCorrespondence to: C. Córdoba-Jabonero (cordobajc@inta.es) of coarse particles during those dusty events. Lidar observations characterized their vertical layering structure, identifying different aerosol contributions depending on altitude. In particular, the 3-km height dust layer transported from the Saharan region and observed over SCO site was later on detected at ARN and GRA stations. No significant differences were found in the lidar (extinction-to-backscatter) ratio (LR) estimation for that dust plume over all stations when a suitable aerosol scenario for lidar data retrieval is selected. Lidar-retrieved LR values of 60-70 sr were obtained during the main dust episodes. These similar LR values found in all the stations suggest that dust properties were kept nearly unchanged in the course of its medium-range transport. In addition, the potential impact on surface of that Saharan dust intrusion over the Iberian Peninsula was evaluated by means of ground-level in-situ measurements for particle deposition assessment together with backtrajectory analysis. However, no connection between those dust plumes and the particle sedimentation registered at ground level is found. Differences on particle deposition processes observed in both Southern Iberian Peninsula sites are due to the particular dust transport pattern occurred over each station. Discrepancies between columnar-integrated and ground-level in-situ measurements show a clear dependence on height of the dust particle size distribution. Then, further vertical size-resolved observations are needed for evaluation of the impact on surface of the Saharan dust arrival to the Iberian Peninsula.

Several procedures are widely applied to estimate the atmospheric boundary layer (ABL) top height by using aerosols as tracers from lidar measurements. These methods represent different mathematical approaches, relying on either the abrupt step of the aerosol concentration between the ABL and the free troposphere (FT) or the statistical analysis of vertical variations of the aerosol concentration. An alternative method-the cluster analysis (CA)-has been applied to lidar measurements for the first time, emerging as a useful and robust approach for calculating the ABL height, taking the advantage of both previous variables: the vertical aerosol distribution as obtained from the lidar range-corrected signal (RCS) and the statistical analysis of the RCS profiles in terms of its variance to determine a region of high aerosol loading variability. CA limitations under real situations are also tested, and the effects in ABL height determination of both noise and cloud contamination in RCS are examined. In particular, CA results are weakly sensitive to the signal noise due to the basic features of this statistical method. In addition, differences in the ABL top height, as estimated under cloudy and clear skies, have been found to be lower than 1.8% for a high RCS signal, while no effect is observed for low RCS cloud conditions. Moreover, the CA performance on the ABL top height determination for real cases is also presented, showing the reliable CA skills in reproducing the ABL evolution.

Abstract. The application of the POLIPHON (POlarizationLIdar PHOtometer Networking) method is presented for the first time in synergy with continuous 24/7 polarized MicroPulse Lidar (P-MPL) measurements to derive the vertical separation of two or three particle components in different aerosol mixtures, and the retrieval of their particular optical properties. The procedure of extinction-to-mass conversion, together with an analysis of the mass extinction efficiency (MEE) parameter, is described, and the relative mass contribution of each aerosol component is also derived in a further step. The general POLIPHON algorithm is based on the specific particle linear depolarization ratio given for different types of aerosols and can be run in either 1-step (POL-1) or 2 steps (POL-2) versions with dependence on either the 2-or 3-component separation. In order to illustrate this procedure, aerosol mixing cases observed over Barcelona (NE Spain) are selected: a dust event on 5 July 2016, smoke plumes detected on 23 May 2016 and a pollination episode observed on 23 March 2016. In particular, the 3-component separation is just applied for the dust case: a combined POL-1 with POL-2 procedure (POL-1/2) is used, and additionally the fine-dust contribution to the total fine mode (fine dust plus non-dust aerosols) is estimated. The high dust impact before 12:00 UTC yields a mean mass loading of 0.6 ± 0.1 g m −2 due to the prevalence of Saharan coarse-dust particles. After that time, the mean mass loading is reduced by two-thirds, showing a rather weak dust incidence. In the smoke case, the arrival of fine biomass-burning particles is detected at altitudes as high as 7 km. The smoke particles, probably mixed with less depolarizing non-smoke aerosols, are observed in air masses, having their origin from either North American fires or the Arctic area, as reported by HYSPLIT backtrajectory analysis. The particle linear depolarization ratio for smoke shows values in the 0.10-0.15 range and even higher at given times, and the daily mean smoke mass loading is 0.017 ± 0.008 g m −2 , around 3 % of that found for the dust event. Pollen particles are detected up to 1.5 km in height from 10:00 UTC during an intense pollination event with a particle linear depolarization ratio ranging between 0.10 and 0.15. The maximal mass loading of Platanus pollen particles is 0.011 ± 0.003 g m −2 , representing around 2 % of the dust loading during the higher dust incidence. Regarding the MEE derived for each aerosol component, their values are in agreement with others referenced in the literature for the specific aerosol types examined in this work: 0.5 ± 0.1 and 1.7 ± 0.2 m 2 g −1 are found for coarse and fine dust particles, 4.5 ± 1.4 m 2 g −1 is derived for smoke and 2.4 ± 0.5 m 2 g −1 for non-smoke aerosols with Arctic origin, and a MEE of 2.4 ± 0.8 m 2 g −1 is obtained for pollen particles, though it can reach higher or lower values depending on predomiPublished by Copernicus Publications on behalf of the European Geosciences Union. 4776 C. Córdoba...