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- ItemThe influence of geomagnetic activity on mesospheric summer echoes in middle and polar latitudes(München : European Geopyhsical Union, 2009) Zeller, O.; Bremer, J.The dependence of mesospheric VHF radar echoes during summer months on geomagnetic activity has been investigated with observation data of the OSWIN radar in Kühlungsborn (54° N) and of the ALWIN radar in Andenes (69° N). Using daily mean values of VHF radar echoes and of geomagnetic activity indices in superimposed epoch analyses, the comparison of both data sets shows in general stronger radar echoes on the day of the maximum geomagnetic activity, the maximum value one day after the geomagnetic disturbance, and enhanced radar echoes also on the following 2–3 days. This phenomenon is observed at middle and polar latitudes and can be explained by precipitating particle fluxes during the ionospheric post storm effect. At polar latitudes, the radar echoes decrease however during and one day after very strong geomagnetic disturbances. The possible reason of this surprising effect is discussed.
- ItemPolar middle atmosphere temperature climatology from Rayleigh lidar measurements at ALOMAR (69° N)(München : European Geopyhsical Union, 2008) Schöch, A.; Baumgarten, G.; Fiedler, J.Rayleigh lidar temperature profiles have been derived in the polar middle atmosphere from 834 measurements with the ALOMAR Rayleigh/Mie/Raman lidar (69.3° N, 16.0° E) in the years 1997–2005. Since our instrument is able to operate under full daylight conditions, the unique data set presented here extends over the entire year and covers the altitude region 30 km–85 km in winter and 30 km–65 km in summer. Comparisons of our lidar data set to reference atmospheres and ECMWF analyses show agreement within a few Kelvin in summer but in winter higher temperatures below 55 km and lower temperatures above by as much as 25 K, due likely to superior resolution of stratospheric warming and associated mesospheric cooling events. We also present a temperature climatology for the entire lower and middle atmosphere at 69° N obtained from a combination of lidar measurements, falling sphere measurements and ECMWF analyses. Day to day temperature variability in the lidar data is found to be largest in winter and smallest in summer.
- ItemEARLINET instrument intercomparison campaigns: Overview on strategy and results(München : European Geopyhsical Union, 2016) Wandinger, Ulla; Freudenthaler, Volker; Baars, Holger; Amodeo, Aldo; Engelmann, Ronny; Mattis, Ina; Groß, Silke; Pappalardo, Gelsomina; Giunta, Aldo; D'Amico, Giuseppe; Chaikovsky, Anatoli; Osipenko, Fiodor; Slesar, Alexander; Nicolae, Doina; Belegante, Livio; Talianu, Camelia; Serikov, Ilya; Linné, Holger; Jansen, Friedhelm; Apituley, Arnoud; Wilson, Keith M.; de Graaf, Martin; Trickl, Thomas; Giehl, Helmut; Adam, Mariana; Comerón, Adolfo; Muñoz-Porcar, Constantino; Rocadenbosch, Francesc; Sicard, Michaël; Tomás, Sergio; Lange, Diego; Kumar, Dhiraj; Pujadas, Manuel; Molero, Francisco; Fernández, Alfonso J.; Alados-Arboledas, Lucas; Bravo-Aranda, Juan Antonio; Navas-Guzmán, Francisco; Guerrero-Rascado, Juan Luis; Granados-Muñoz, María José; Preißler, Jana; Wagner, Frank; Gausa, Michael; Grigorov, Ivan; Stoyanov, Dimitar; Iarlori, Marco; Rizi, Vincenco; Spinelli, Nicola; Boselli, Antonella; Wang, Xuan; Feudo, Teresa Lo; Perrone, Maria Rita; De Tomas, Ferdinando; Burlizzi, PasqualeThis 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 607 nm. 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 × 10−4 km−1 sr−1 and ± 0.01 km−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.
- ItemMALTE - Model to predict new aerosol formation in the lower troposphere(München : European Geopyhsical Union, 2006) Boy, M.; Hellmuth, O.; Korhonen, H.; Nilsson, E.D.; ReVelle, D.; Turnipseed, A.; Arnold, F.; Kulmala, M.The manuscript presents a detailed description of the meteorological and chemical code of Malte – a model to predict new aerosol formation in the lower troposphere. The aerosol dynamics are achieved by the new developed UHMA (University of Helsinki Multicomponent Aerosol Model) code with kinetic limited nucleation as responsible mechanism to form new clusters. First results indicate that the model is able to predict the on- and offset of new particle formation as well as the total aerosol number concentrations that were in good agreement with the observations. Further, comparison of predicted and measured H2SO4 concentrations showed a satisfactory agreement. The simulation results indicated that at a certain transitional particle diameter (2–7 nm), organic molecules can begin to contribute significantly to the growth rate compared to sulphuric acid. At even larger particle sizes, organic molecules can dominate the growth rate on days with significant monoterpene concentrations. The intraday vertical evolution of newly formed clusters and particles in two different size ranges resulted in two maxima at the ground. These particles grow around noon to the detectable size range and agree well with measured vertical profiles.
- ItemThe influence of vegetation, fire spread and fire behaviour on biomass burning and trace gas emissions: Results from a process-based model(München : European Geopyhsical Union, 2010) Thonicke, K.; Spessa, A.; Prentice, I.C.; Harrison, S.P.; Dong, L.; Carmona-Moreno, C.A process-based fire regime model (SPITFIRE) has been developed, coupled with ecosystem dynamics in the LPJ Dynamic Global Vegetation Model, and used to explore fire regimes and the current impact of fire on the terrestrial carbon cycle and associated emissions of trace atmospheric constituents. The model estimates an average release of 2.24 Pg C yr−1 as CO2 from biomass burning during the 1980s and 1990s. Comparison with observed active fire counts shows that the model reproduces where fire occurs and can mimic broad geographic patterns in the peak fire season, although the predicted peak is 1–2 months late in some regions. Modelled fire season length is generally overestimated by about one month, but shows a realistic pattern of differences among biomes. Comparisons with remotely sensed burnt-area products indicate that the model reproduces broad geographic patterns of annual fractional burnt area over most regions, including the boreal forest, although interannual variability in the boreal zone is underestimated.
- ItemACTRIS ACSM intercomparison - Part 1: Reproducibility of concentration and fragment results from 13 individual Quadrupole Aerosol Chemical Speciation Monitors (Q-ACSM) and consistency with co-located instruments(München : European Geopyhsical Union, 2015) Crenn, V.; Sciare, J.; Croteau, P.L.; Verlhac, S.; Fröhlich, R.; Belis, C.A.; Aas, W.; Äijälä, M.; Alastuey, A.; Artiñano, B.; Baisnée, D.; Bonnaire, N.; Bressi, M.; Canagaratna, M.; Canonaco, F.; Carbone, C.; Cavalli, F.; Coz, E.; Cubison, M.J.; Esser-Gietl, J.K.; Green, D.C.; Gros, V.; Heikkinen, L.; Herrmann, H.; Lunder, C.; Minguillón, M.C.; Močnik, G.; O'Dowd, C.D.; Ovadnevaite, J.; Petit, J.-E.; Petralia, E.; Poulain, L.; Priestman, M.; Riffault, V.; Ripoll, A.; Sarda-Estève, R.; Slowik, J.G.; Setyan, A.; Wiedensohler, A.; Baltensperger, U.; Prévôt, A.S.H.; Jayne, J.T.; Favez, O.As part of the European ACTRIS project, the first large Quadrupole Aerosol Chemical Speciation Monitor (Q-ACSM) intercomparison study was conducted in the region of Paris for 3 weeks during the late-fall – early-winter period (November–December 2013). The first week was dedicated to the tuning and calibration of each instrument, whereas the second and third were dedicated to side-by-side comparison in ambient conditions with co-located instruments providing independent information on submicron aerosol optical, physical, and chemical properties. Near real-time measurements of the major chemical species (organic matter, sulfate, nitrate, ammonium, and chloride) in the non-refractory submicron aerosols (NR-PM1) were obtained here from 13 Q-ACSM. The results show that these instruments can produce highly comparable and robust measurements of the NR-PM1 total mass and its major components. Taking the median of the 13 Q-ACSM as a reference for this study, strong correlations (r2 > 0.9) were observed systematically for each individual Q-ACSM across all chemical families except for chloride for which three Q-ACSMs showing weak correlations partly due to the very low concentrations during the study. Reproducibility expanded uncertainties of Q-ACSM concentration measurements were determined using appropriate methodologies defined by the International Standard Organization (ISO 17025, 1999) and were found to be 9, 15, 19, 28, and 36 % for NR-PM1, nitrate, organic matter, sulfate, and ammonium, respectively. However, discrepancies were observed in the relative concentrations of the constituent mass fragments for each chemical component. In particular, significant differences were observed for the organic fragment at mass-to-charge ratio 44, which is a key parameter describing the oxidation state of organic aerosol. Following this first major intercomparison exercise of a large number of Q-ACSMs, detailed intercomparison results are presented, along with a discussion of some recommendations about best calibration practices, standardized data processing, and data treatment.
- ItemIntercomparison of air ion spectrometers: An evaluation of results in varying conditions(München : European Geopyhsical Union, 2011) Gagné, S.; Lehtipalo, K.; Manninen, H.E.; Nieminen, T.; Schobesberger, S.; Franchin, A.; Yli-Juuti, T.; Boulon, J.; Sonntag, A.; Mirme, S.; Mirme, A.; Hõrrak, U.; Petäjä, T.; Asmi, E.; Kulmala, M.We evaluated 11 air ion spectrometers from Airel Ltd. after they had spent one year in field measurements as a part of the EUCAARI project: 5 Air Ion Spectrometers (AIS), 5 Neutral cluster and Air Ion Spectrometers (NAIS) and one Airborne NAIS (ANAIS). This is the first time that an ANAIS is evaluated and compared so extensively. The ion spectrometers' mobility and concentration accuracy was evaluated. Their measurements of ambient air were compared between themselves and to reference instruments: a Differential Mobility Particle Sizer (DMPS), a Balanced Scanning Mobility Analyzer (BSMA), and an Ion-DMPS. We report on the simultaneous measurement of a new particle formation (NPF) event by all 11 instruments and the 3 reference instruments. To our knowledge, it is the first time that the size distribution of ions and particles is measured by so many ion spectrometers during a NPF event. The new particle formation rates (~0.2 cm−3 s−1 for ions and ~2 cm−3 s−1 for particles) and growth rates (~25 nm h−1 in the 3–7 nm size range) were calculated for all the instruments. The NAISs and the ANAIS gave higher concentrations and formation rates than the AISs. For example, the AISs agreed with the BSMA within 11 % and 28 % for negative and positive ion concentration respectively, whereas the NAISs agreed within 23 % and 29 %. Finally, based on the results presented here, we give guidelines for data evaluation, when data from different individual ion spectrometers are compared.
- ItemMaritime aerosol network as a component of AERONET - First results and comparison with global aerosol models and satellite retrievals(München : European Geopyhsical Union, 2011) Smirnov, A.; Holben, B.N.; Giles, D.M.; Slutsker, I.; O'Neill, N.T.; Eck, T.F.; Macke, A.; Croot, P.; Courcoux, Y.; Sakerin, S.M.; Smyth, T.J.; Zielinski, T.; Zibordi, G.; Goes, J.I.; Harvey, M.J.; Quinn, P.K.; Nelson, N.B.; Radionov, V.F.; Duarte, C.M.; Losno, R.; Sciare, J.; Voss, K.J.; Kinne, S.; Nalli, N.R.; Joseph, E.; Krishna Moorthy, K.; Covert, D.S.; Gulev, S.K.; Milinevsky, G.; Larouche, P.; Belanger, S.; Horne, E.; Chin, M.; Remer, L.A.; Kahn, R.A.; Reid, J.S.; Schulz, M.; Heald, C.L.; Zhang, J.; Lapina, K.; Kleidman, R.G.; Griesfeller, J.; Gaitley, B.J.; Tan, Q.; Diehl, T.L.The Maritime Aerosol Network (MAN) has been collecting data over the oceans since November 2006. Over 80 cruises were completed through early 2010 with deployments continuing. Measurement areas included various parts of the Atlantic Ocean, the Northern and Southern Pacific Ocean, the South Indian Ocean, the Southern Ocean, the Arctic Ocean and inland seas. MAN deploys Microtops hand-held sunphotometers and utilizes a calibration procedure and data processing traceable to AERONET. Data collection included areas that previously had no aerosol optical depth (AOD) coverage at all, particularly vast areas of the Southern Ocean. The MAN data archive provides a valuable resource for aerosol studies in maritime environments. In the current paper we present results of AOD measurements over the oceans, and make a comparison with satellite AOD retrievals and model simulations.
- ItemMultichannel analysis of correlation length of SEVIRI images around ground-based cloud observatories to determine their representativeness(München : European Geopyhsical Union, 2015) Slobodda, J.; Hünerbein, A.; Lindstrot, R.; Preusker, R.; Ebell, K.; Fischer, J.Images of measured radiance in different channels of the geostationary Meteosat-9 SEVIRI instrument are analysed with respect to the representativeness of the observations of eight cloud observatories in Europe (e.g. measurements from cloud radars or microwave radiometers). Cloudy situations are selected to get a time series for every pixel in a 300 km × 300 km area centred around each ground station. Then a cross correlation of each time series to the pixel nearest to the corresponding ground site is calculated. In the end a correlation length is calculated to define the representativeness. It is found that measurements in the visible and near infrared channels, which respond to cloud physical properties, are correlated in an area with a 1 to 4 km radius, while the thermal channels, that correspond to cloud top temperature, are correlated to a distance of about 20 km. This also points to a higher variability of the cloud microphysical properties inside a cloud than of the cloud top temperature. The correlation length even increases for the channels at 6.2, 7.3 and 9.7 μm. They respond to radiation from the upper atmospheric layers emitted by atmospheric gases and higher level clouds, which are more homogeneous than low-level clouds. Additionally, correlations at different distances, corresponding to the grid box sizes of forecast models, were compared. The results suggest the possibility of comparisons between instantaneous cloud observations from ground sites and regional forecast models and ground-based measurements. For larger distances typical for global models the correlations decrease, especially for short-wave measurements and corresponding cloud products. By comparing daily means, the correlation length of each station is increased to about 3 to 10 times the value of instantaneous measurements and also the comparability to models grows.
- ItemCeilometer lidar comparison: Backscatter coefficient retrieval and signal-to-noise ratio determination(München : European Geopyhsical Union, 2010) Heese, B.; Flentje, H.; Althausen, D.; Ansmann, A.; Frey, S.The potential of a new generation of ceilometer instruments for aerosol monitoring has been studied in the Ceilometer Lidar Comparison (CLIC) study. The used ceilometer was developed by Jenoptik, Germany, and is designed to find both thin cirrus clouds at tropopause level and aerosol layers at close ranges during day and night-time. The comparison study was performed to determine up to which altitude the ceilometers are capable to deliver particle backscatter coefficient profiles. For this, the derived ceilometer profiles are compared to simultaneously measured lidar profiles at the same wavelength. The lidar used for the comparison was the multi-wavelengths Raman lidar PollyXT. To demonstrate the capabilities and limits of ceilometers for the derivation of particle backscatter coefficient profiles from their measurements two examples of the comparison results are shown. Two cases, a daytime case with high background noise and a less noisy night-time case, are chosen. In both cases the ceilometer profiles compare well with the lidar profiles in atmospheric structures like aerosol layers or the boundary layer top height. However, the determination of the correct magnitude of the particle backscatter coefficient needs a calibration of the ceilometer data with an independent measurement of the aerosol optical depth by a sun photometer. To characterizes the ceilometers signal performance with increasing altitude a comprehensive signal-to-noise ratio study was performed. During daytime the signal-to-noise ratio is higher than 1 up to 4–5 km depending on the aerosol content. In our night-time case the SNR is higher than 1 even up to 8.5 km, so that also aerosol layers in the upper troposphere had been detected by the ceilometer.