Wandinger U.,Leibniz Institute for Tropospheric Research |
Freudenthaler V.,Ludwig Maximilians University of Munich |
Baars H.,Leibniz Institute for Tropospheric Research |
Amodeo A.,CNR Institute of Methodologies for Environmental analysis |
And 69 more authors.
Atmospheric Measurement Techniques | Year: 2016
This paper introduces the recent European Aerosol Research Lidar Network (EARLINET) quality-assurance efforts at instrument level. Within two dedicated campaigns and five single-site intercomparison activities, 21 EARLINET systems from 18 EARLINET stations were intercompared between 2009 and 2013. A comprehensive strategy for campaign setup and data evaluation has been established. Eleven systems from nine EARLINET stations participated in the EARLINET Lidar Intercomparison 2009 (EARLI09). In this campaign, three reference systems were qualified which served as traveling standards thereafter. EARLINET systems from nine other stations have been compared against these reference systems since 2009. We present and discuss comparisons at signal and at product level from all campaigns for more than 100 individual measurement channels at the wavelengths of 355, 387, 532, and 607nm. It is shown that in most cases, a very good agreement of the compared systems with the respective reference is obtained. Mean signal deviations in predefined height ranges are typically below ±2%. Particle backscatter and extinction coefficients agree within ±2 × 10-4km-1 and ±0.01km-1, respectively, in most cases. For systems or channels that showed larger discrepancies, an in-depth analysis of deficiencies was performed and technical solutions and upgrades were proposed and realized. The intercomparisons have reinforced confidence in the EARLINET data quality and allowed us to draw conclusions on necessary system improvements for some instruments and to identify major challenges that need to be tackled in the future. © Author(s) 2016.
Petkov B.H.,CNR Institute of atmospheric Sciences and Climate |
Petkov B.H.,Abdus Salam International Center For Theoretical Physics |
Vitale V.,CNR Institute of atmospheric Sciences and Climate |
Tomasi C.,CNR Institute of atmospheric Sciences and Climate |
And 25 more authors.
Atmospheric Environment | Year: 2014
The strong ozone depletion event that occurred in Arctic during spring 2011 was found to cause appreciable reduction in the ozone column (OC) in Europe, even at lower latitudes. The features of this episode have been analysed using the data recorded at 34 ground-based stations located in the European area and compared with the similar events in 2000 and 2005. The results provided evidence that OC as far south as 40°N latitude was considerably influenced by the Arctic ozone loss in spring 2011. The reduction of OC at the northernmost sites was about 40% with respect to the mean value calculated over the previous six-year period, while a similar decrease at the southern extreme ranged between 15 and 18%, and were delayed by nearly two weeks compared to the Arctic region. The ozone distributions reconstructed for the West Europe sector show that the decline of OC lasted from late March to late April 2011. The echo of the Arctic ozone depletion on mid-latitude UV irradiance has been analysed trough model computations that show an increase of the midday erythemal dose by 3-4 SED (1 SED=100Jm-2) that was slightly higher than at polar regions. On the other hand it was assessed that the biosystems in the northernmost regions were a subject of about 4 times higher UV stress than those at mid-latitudes. Despite indications of an OC recovery, the event examined here shows that the issue of ozone depletion episodes cannot be belittled. © 2013 Elsevier Ltd.
Paasonen P.,University of Helsinki |
Nieminen T.,University of Helsinki |
Asmi E.,Finnish Meteorology Institute |
Manninen H.E.,University of Helsinki |
And 15 more authors.
Atmospheric Chemistry and Physics | Year: 2010
Sulphuric acid and organic vapours have been identified as the key components in the ubiquitous secondary new particle formation in the atmosphere. In order to assess their relative contribution and spatial variability, we analysed altogether 36 new particle formation events observed at four European measurement sites during EUCAARI campaigns in 2007-2009. We tested models of several different nucleation mechanisms coupling the formation rate of neutral particles (J) with the concentration of sulphuric acid ([H2SO 4]) or low-volatility organic vapours ([org]) condensing on sub-4 nm particles, or with a combination of both concentrations. Furthermore, we determined the related nucleation coefficients connecting the neutral nucleation rate J with the vapour concentrations in each mechanism. The main goal of the study was to identify the mechanism of new particle formation and subsequent growth that minimizes the difference between the modelled and measured nucleation rates. At three out of four measurement sites - Hyytiälä (Finland), Melpitz (Germany) and San Pietro Capofiume (Italy)-the nucleation rate was closely connected to squared sulphuric acid concentration, whereas in Hohenpeissenberg (Germany) the low-volatility organic vapours were observed to be dominant. However, the nucleation rate at the sulphuric acid dominant sites could not be described with sulphuric acid concentration and a single value of the nucleation coefficient, as K in J Combining double low line K [H 2SO4]2, but the median coefficients for different sites varied over an order of magnitude. This inter-site variation was substantially smaller when the heteromolecular homogenous nucleation between H2SO4 and organic vapours was assumed to take place in addition to homogenous nucleation of H2SO4 alone, i.e., J Combining double low line KSA1[H2SO4] 2+KSA2[H2SO4][org]. By adding in this equation a term describing homomolecular organic vapour nucleation, K s3[org]2, equally good results were achieved. In general, our results suggest that organic vapours do play a role, not only in the condensational growth of the particles, but also in the nucleation process, with a site-specific degree. © 2010 Author(s).
Logan J.A.,Harvard University |
Staehelin J.,ETH Zurich |
Megretskaia I.A.,Harvard University |
Cammas J.-P.,CNRS Laboratory for Aerology |
And 10 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2012
We use ozone observations from sondes, regular aircraft, and alpine surface sites in a self-consistent analysis to determine robust changes in the time evolution of ozone over Europe. The data are most coherent since 1998, with similar interannual variability and trends. Ozone has decreased slowly since 1998, with an annual mean trend of-0.15ppbyr-1 at ∼3km and the largest decrease in summer. There are some substantial differences between the sondes and other data, particularly in the early 1990s. The alpine and aircraft data show that ozone increased from late 1994 until 1998, but the sonde data do not. Time series of differences in ozone between pairs of locations reveal inconsistencies in various data sets. Differences as small as few ppb for 2-3years lead to different trends for 1995-2008, when all data sets overlap. Sonde data from Hohenpeissenberg and in situ data from nearby Zugspitze show ozone increased by ∼1ppbyr-1 during 1978-1989. We construct a mean alpine time series using data for Jungfraujoch, Zugspitze, and Sonnblick. Using Zugspitze data for 1978-1989, and the mean time series since 1990, we find that the ozone increased by 6.5-10ppb in 1978-1989 and 2.5-4.5ppb in the 1990s and decreased by 4ppb in the 2000s in summer with no significant changes in other seasons. It is hard to reconcile all these changes with trends in emissions of ozone precursors, and in ozone in the lowermost stratosphere. We recommend data sets that are suitable for evaluation of model hindcasts. Copyright 2012 by the American Geophysical Union.