Description: Two years of continuous in situ measurements of Arctic low‐level clouds have been made at the Mount Zeppelin Observatory (78°56′N, 11°53′E), in Ny‐Ålesund, Spitsbergen. The monthly median value of the cloud particle number concentration (Nc) showed a clear seasonal variation: Its maximum appeared in May–July (65 ± 8 cm−3), and it remained low between October and March (8 ± 7 cm−3). At temperatures warmer than 0 °C, a clear correlation was found between the hourly Nc values and the number concentrations of aerosols with dry diameters larger than 70 nm (N70), which are proxies for cloud condensation nuclei (CCN). When clouds were detected at temperatures colder than 0 °C, some of the data followed the summertime Nc to N70 relationship, while other data showed systematically lower Nc values. The lidar‐derived depolarization ratios suggested that the former (CCN‐controlled) and latter (CCN‐uncontrolled) data generally corresponded to clouds consisting of supercooled water droplets and those containing ice particles, respectively. The CCN‐controlled data persistently appeared throughout the year at Zeppelin. The aerosol‐cloud interaction index (ACI = dlnNc/(3dlnN70)) for the CCN‐controlled data showed high sensitivities to aerosols both in the summer (clean air) and winter–spring (Arctic haze) seasons (0.22 ± 0.03 and 0.25 ± 0.02, respectively). The air parcel model calculations generally reproduced these values. The threshold diameters of aerosol activation (Dact), which account for the Nc of the CCN‐controlled data, were as low as 30–50 nm when N70 was less than 30 cm−3, suggesting that new particle formation can affect Arctic cloud microphysics.

Description: A closure experiment was conducted over Svalbard by comparing Lidar measurements and optical aerosol properties calculated from aerosol vertical profiles measured using a tethered balloon. Arctic Haze was present together with Icelandic dust. Chemical analysis of filter samples, aerosol size distribution and a full set of meteorological parameters were determined at ground. Moreover, scanning electron microscopy coupled with energy-dispersive X-ray (SEM-EDS) data were at disposal showing the presence of several mineralogical phases (i.e., sheet silicates, gypsum, quartz, rutile, hematite). The closure experiment was set up by calculating the backscattering coefficients from tethered balloon data and comparing them with the corresponding lidar profiles. This was preformed in three subsequent steps aimed at determining the importance of a complete aerosol speciation: (i) a simple, columnar refractive index was obtained by the closest Aerosol Robotic Network (AERONET) station, (ii) the role of water-soluble components, elemental carbon and organic matter (EC/OM) was addressed, (iii) the dust composition was included. When considering the AERONET data, or only the ionic water-soluble components and the EC/OM fraction, results showed an underestimation of the backscattering lidar signal up to 76, 53 and 45% (355, 532 and 1064 nm). Instead, when the dust contribution was included, the underestimation disappeared and the vertically-averaged, backscattering coefficients (1.45±0.30, 0.69±0.15 and 0.34±0.08 Mm-1 sr-1, at 355, 532 and 1064 nm) were found in keeping with the lidar ones (1.60±0.22, 0.75±0.16 and 0.31±0.08 Mm-1 sr-1). Final results were characterized by low RMSE (0.36, 0.08 and 0.04 Mm-1 sr-1) and a high linear correlation (R2 of 0.992, 0.992 and 0.994) with slopes close to one (1.368, 0.931 and 0.977, respectively). This work highlighted the importance of all the aerosol components and of the synergy between single particle and bulk chemical analysis for the optical property characterization in the Arctic .

Description: Abstract New particle formation in the Arctic atmosphere is an important source of aerosol particles. Understanding the processes of Arctic secondary aerosol formation is crucial due to their significant impact on cloud properties and therefore Arctic amplification. We observed the molecular formation of new particles from low-volatility vapors at two Arctic sites with differing surroundings. In Svalbard, sulfuric acid (SA) and methane sulfonic acid (MSA) contribute to the formation of secondary aerosol and to some extent to cloud condensation nuclei (CCN). This occurs via ion-induced nucleation of SA and NH3 and subsequent growth by mainly SA and MSA condensation during springtime and highly oxygenated organic molecules during summertime. By contrast, in an ice-covered region around Villum, we observed new particle formation driven by iodic acid but its concentration was insufficient to grow nucleated particles to CCN sizes. Our results provide new insight about sources and precursors of Arctic secondary aerosol particles.

Description: Multitudes of measurements are needed to understand the environment and its evolution. The Arctic region is a fundamental observation area for climate change evaluation: climate change comes first and comes faster in the Arctic. The higher accuracy required to quickly capture trends; the extreme range and conditions of sensors exposure; a robust comparability asked by the different measurement networks; the need of dedicated calibration procedures, together with the logistical problems associated with such remote location, motivate the proposal for a joint effort to address metrology experience and activities for Arctic research applications. The Ny-Ålesund international research base and community offers a unique infrastructure to directly link metrological traceability to on site polar measurements. The contribution reports a study on the implementation of specific calibration procedures, metrological validation of measurements and instrument tests, uncertainties evaluations including quantities of influence, and the feasibility of a metrology laboratory in Ny-Ålesund.

Description: We present results from a systematic study of vertical profiles of aerosol number size distribution and black carbon (BC) concentrations conducted in the Arctic, over Ny-Ålesund (Svalbard). The campaign lasted 2 years (2011–2012) and resulted in 200 vertical profiles measured by means of a tethered balloon (up to 1200 m a.g.l.) during the spring and summer seasons. In addition, chemical analysis of filter samples, aerosol size distribution and a full set of meteorological parameters were determined at ground. The collected experimental data allowed a classification of the vertical profiles into different typologies, which allowed us to describe the seasonal phenomenology of vertical aerosol properties in the Arctic. During spring, four main types of profiles were found and their behavior was related to the main aerosol and atmospheric dynamics occurring at the measuring site. Background conditions generated homogenous profiles. Transport events caused an increase of aerosol concentration with altitude. High Arctic haze pollution trapped below thermal inversions promoted a decrease of aerosol concentration with altitude. Finally, ground-based plumes of locally formed secondary aerosol determined profiles with decreasing aerosol concentration located at different altitude as a function of size. During the summer season, the impact from shipping caused aerosol and BC pollution plumes to be constrained close to the ground, indicating that increasing shipping emissions in the Arctic could bring anthropogenic aerosol and BC in the Arctic summer, affecting the climate.

Description: In November 2008, Svalbard Science Forum organised a workshop with the aim to discuss future focal areas in atmosphere research in Ny-Ålesund. The result is this document that initiates an Atmosphere Research Flagship programme as part of the NySMAC science plan for Ny-Ålesund. In Ny-Ålesund, long term measurements of several key climate parameters from the surface level up to the ozone layer have been performed for decades already. Such comprehensive data sets are available from very few sites in the Arctic and the data are continuously fed into global networks. Ny-Ålesund offers excellent conditions for scientific research, due to its accessibility and international and multidisciplinary character. For atmospheric research, Ny-Ålesund offers the possibility to perform continuous measurements both close at sea level and at 475 m of altitude within a relatively pristine environment. Also, its location under the magnetospheric cusp makes it a unique place for observing the solar wind and magnetosphere interaction on the dayside. In order to optimally use these excellent conditions for atmospheric research and to improve cooperation within the Kongsfjorden science community, this document describes general flagship goals which include the optimal utilization of available instruments and data sets, the establishment and further development of common research infrastructures, and a programme to investigate the representativeness of measurements in Ny-Ålesund for climate change research and atmospheric process studies. The flagship programme states the following future research priorities: • Long term observations of key parameters concerning climate change • Planetary boundary layer (PBL) research • Studies and monitoring of long range transport of pollutants • Arctic ozone layer and UV research • Ionospheric / magnetospheric research • Validation and synergistic analyses of satellite data The flagship programme aims to establish a unique international long-term atmospheric monitoring and observation platform supported by all research institutions represented in Ny-Ålesund and thus to realize a supersite, allowing investigations of the complex Arctic System with a multidisciplinary approach. Interdisciplinary observations will be performed elucidating interaction processes on sea, snow and ice surfaces and the atmosphere. Special emphasis will be laid upon the impact of climate change on the Arctic environment. Furthermore, means of better integration of atmospheric research within NyÅlesund, Svalbard as well as on a circumpolar level are discussed, and possibilities for interdisciplinary cooperation with other flagships are pointed out. Finally, three appendices give an overview of atmospheric stations in Ny-Ålesund, atmospheric parameters measured in Ny-Ålesund, and the atmospheric monitoring satellites in operation in 2010–2020.

Description: The Arctic research village of Ny-Ålesund (79 ° N, 12 ° E) on the Spitsbergen island of Svalbard archipelago, with its logistics and infrastructure, provides a unique access to the Arctic environment. Among the several international environmental and climate monitoring programmes constantly running there, the Global Climate Observing System (GCOS) Reference Upper Air Network (GRUAN) has established one of its stations at the Alfred Wegener Institute observatory. Calibration of sensors and measurement traceability are fundamental aspects of climate observations, as requested by the GRUAN measurement procedures. In the framework of the MeteoMet project, a transportable climatic chamber for the calibrations of air temperature and pressure sensors was studied and manufactured. In June 2014, a calibration campaign involved the transport and use of one of those systems in the Ny-Ålesund GRUAN station. The result of the campaign has been the complete calibration of temperature and pressure sensors for radiosonde pre-launch ground checks. The resulting calibration curves were obtained with lower uncertainties and more robust characterization of the sensors, with respect to the usual procedures adopted. Given the opportunity of the calibration device operating already in place and the presence of the metrology staff, the calibration was extended to the sensors equipping the Amundsen-Nobile Climate Change Tower. The present study reports on the ‘Arctic metrology 2014’ campaign and the plans for the establishment of a permanent laboratory for metrology in Ny-Ålesund. The aim is to address the measurement traceability needs arising from the multidisciplinary measurements made by the scientific community operating there.

Description: The International workshop on Atmospheric Studies in the Arctic was held at the Institute of Oceanology, Polish Academy of Sciences in Sopot, Poland on 28. and 29. January 2016. The workshop is a joint effort of the iAREA team, the Alfred Wegener Institute and the University of Florence in cooperation with the Institute of Oceanology, Polish Academy of Sciences and the Center for Polar Studies. The workshop is a contribution to the Ny-Aalesund Atmosphere Flagship Programme. This book of abstract includes the contributions building on the iAREA campaigns in 2014 and 2015 held in Ny-Aalesund, Spitsbergen.