ALBERT

Description: During the BALTIC'15 campaign, conducted in August 2015 over the Southern Baltic Sea, trace gasses (CO2/O3/NOy/SO2) and aerosol particles (number concentration of total/non-volatile/Aitken mode/ Accumulation mode/Coarse mode/refractory black carbon, aerosol extinction coefficient, mass concentration of refractory black carbon were measured). Observations were performed on board of the Alfred Wegener Institute research aircraft Polar 5 during 4 flights: - Scientific flight 1 (SF1) 26 August 2015 - Scientific flight 2 (SF2) 28 August 2015 - Scientific flight 3 (SF3) 28 August 2015 - Scientific flight 4 (SF4) 30 August 2015

Description: During the BALTIC'15 campaign, conducted in August 2015 over the Southern Baltic Sea, trace gasses (CO2/O3/NOy/SO2) and aerosol particles (number concentration of total/non-volatile/Aitken mode/ Accumulation mode/Coarse mode/refractory black carbon, aerosol extinction coefficient, mass concentration of refractory black carbon were measured). Observations were performed on board of the Alfred Wegener Institute research aircraft Polar 5 during flight: - Scientific flight 2 (SF2) 28 August 2015 (BalticSea_2015_1508280401).

Description: During the BALTIC'15 campaign, conducted in August 2015 over the Southern Baltic Sea, trace gasses (CO2/O3/NOy/SO2) and aerosol particles (number concentration of total/non-volatile/Aitken mode/ Accumulation mode/Coarse mode/refractory black carbon, aerosol extinction coefficient, mass concentration of refractory black carbon were measured). Observations were performed on board of the Alfred Wegener Institute research aircraft Polar 5 during flight: - Scientific flight 4 (SF4) 30 August 2015 (BalticSea_2015_1508300601).

Description: During the BALTIC'15 campaign, conducted in August 2015 over the Southern Baltic Sea, trace gasses (CO2/O3/NOy/SO2) and aerosol particles (number concentration of total/non-volatile/Aitken mode/ Accumulation mode/Coarse mode/refractory black carbon, aerosol extinction coefficient, mass concentration of refractory black carbon were measured). Observations were performed on board of the Alfred Wegener Institute research aircraft Polar 5 during flight: - Scientific flight 1 (SF1) 26 August 2015 (BalticSea_2015_1508260301).

Description: During the BALTIC'15 campaign, conducted in August 2015 over the Southern Baltic Sea, trace gasses (CO2/O3/NOy/SO2) and aerosol particles (number concentration of total/non-volatile/Aitken mode/ Accumulation mode/Coarse mode/refractory black carbon, aerosol extinction coefficient, mass concentration of refractory black carbon were measured). Observations were performed on board of the Alfred Wegener Institute research aircraft Polar 5 during flight: - Scientific flight 3 (SF3) 28 August 2015 (BalticSea_2015_1508280502).

Description: The vertical distribution of black carbon (BC) par- ticles in the Arctic atmosphere is one of the key parameters controlling their radiative forcing and thus role in Arctic cli- mate change. This work investigates the presence and prop- erties of these light-absorbing aerosols over the High Cana- dian Arctic ( 〉 70 degree N). Airborne campaigns were performed as part of the NETCARE project (Network on Climate and Aerosols: Addressing Key Uncertainties in Remote Canadian Environments) and provided insights into the variability of the vertical distributions of BC particles in summer 2014 and spring 2015. The observation periods covered evolutions of cyclonic disturbances at the polar front, which favoured the transport of air pollution into the High Canadian Arctic, as otherwise this boundary between the air masses largely im- pedes entrainment of pollution from lower latitudes. A total of 48 vertical profiles of refractory BC (rBC) mass concen- tration and particle size, extending from 0.1 to 5.5 km altitude were obtained with a Single-Particle Soot Photometer (SP2). Generally, the rBC mass concentration decreased from spring to summer by a factor of 10. Such depletion was as- sociated with a decrease in the mean rBC particle diameter, from approximately 200 to 130 nm at low altitude. Due to the very low number fraction, rBC particles did not substantially contribute to the total aerosol population in summer. The analysis of profiles with potential temperature as ver- tical coordinate revealed characteristic variability patterns within specific levels of the cold and stably stratified, dome- like, atmosphere over the polar region. The associated his- tory of transport trajectories into each of these levels showed that the variability was induced by changing rates and effi- ciencies of rBC import. Generally, the source areas affecting the polar dome extended southward with increasing potential temperature (i.e. altitude) level in the dome. While the lower dome was mostly only influenced by low-level transport from sources within the cold central and marginal Arctic, for the mid-dome and upper dome during spring it was found that a cold air outbreak over eastern Europe caused intensified northward transport of air from a corridor over western Rus- sia to central Asia. This sector was affected by emissions from gas flaring, industrial activity and wildfires. The devel- opment of transport caused rBC concentrations in the second lowest level to gradually increase from 32 to 49 ng m

Description: Size-resolved and vertical profile measurements of single particle chemical composition (sampling altitude range 50–3000 m) were conducted in July 2014 in the Cana- dian high Arctic during an aircraft-based measurement cam- paign (NETCARE 2014). We deployed the single parti- cle laser ablation aerosol mass spectrometer ALABAMA (vacuum aerodynamic diameter range approximately 200– 1000 nm) to identify different particle types and their mix- ing states. On the basis of the single particle analysis, we found that a significant fraction (23 %) of all analyzed parti- cles (in total: 7412) contained trimethylamine (TMA). Two main pieces of evidence suggest that these TMA-containing particles originated from emissions within the Arctic bound- ary layer. First, the maximum fraction of particulate TMA occurred in the Arctic boundary layer. Second, compared to particles observed aloft, TMA particles were smaller and less oxidized. Further, air mass history analysis, associated wind data and comparison with measurements of methane- sulfonic acid give evidence of a marine-biogenic influence on particulate TMA. Moreover, the external mixture of TMA- containing particles and sodium and chloride (“Na/Cl-”) containing particles, together with low wind speeds, sug- gests particulate TMA results from secondary conversion of precursor gases released by the ocean. In contrast to TMA- containing particles originating from inner-Arctic sources, particles with biomass burning markers (such as levoglucosan and potassium) showed a higher fraction at higher al- titudes, indicating long-range transport as their source. Our measurements highlight the importance of natural, marine inner-Arctic sources for composition and growth of summer- time Arctic aerosol.

Description: The impact of aerosol spatio-temporal variability on the Arctic radiative budget is not fully constrained. This case study focuses on the intra-Arctic modification of long-range transported aerosol and its direct aerosol radiative effect (ARE). Different types of air-borne and ground-based remote sensing observations (from Lidar and sun-photometer) revealed a high tropospheric aerosol transport episode over two parts of the European Arctic in April 2018. By incorporating the derived aerosol optical and microphysical properties into a radiative transfer model, we assessed the ARE over the two locations. Our study displayed that even in neighboring Arctic upper tropospheric levels, aged aerosol was transformed due to the interplay of removal processes (nucleation scavenging and dry deposition) and alteration of the aerosol source regions (northeast Asia and north Europe). Along the intra-Arctic transport, the coarse aerosol mode was depleted and the visible wavelength Lidar ratio (LR) increased significantly (from 15 to 64–82 sr). However, the aerosol modifications were not reflected on the ARE. More specifically, the short-wave (SW) atmospheric column ARE amounted to +4.4 - +4.9 W m−2 over the ice-covered Fram Strait and +4.5 W m−2 over the snow-covered Ny-Ålesund. Over both locations, top-of-atmosphere (TOA) warming was accompanied by surface cooling. These similarities can be attributed to the predominant accumulation mode, which drives the SW radiative budget, as well as to the similar layer altitude, solar geometry, and surface albedo conditions over both locations. However, in the context of retreating sea ice, the ARE may change even along individual transport episodes due to the ice albedo feedback.

Description: The influence of shipping on air quality over the Southern Baltic Sea was investigated by characterizing the horizontal and vertical distribution of aerosols and trace gases using airborne measurements in the summer of 2015. Generally, continental and anthropogenic emissions affected the vertical distribution of atmospheric pollutants, leading to pronounced stratification in and above the marine boundary layer and controlling the aerosol extinction. Marine traffic along the shipping corridor “Kadet Fairway” in the Arkona Basin is shown to influence the presence and properties of both trace gases and aerosol particles in the lowest atmospheric layer. Total particle number concentration and NOy mixing ratio increased in the corridor plumes, relative to background, by a factor 1.55 and 3.45, respectively. Titration, triggered by the enhanced presence of nitrogen compounds, led to a median ozone depletion of 19% in the corridor plumes. The enforcement of the Sulphur Emission Control Area (SECA) might be responsible for the minor sulphur dioxide increase (20%) in the corridor plumes. Ship traffic caused a minor enhancement of black carbon mass concentration, estimated to be around 10%. The study of individual ship plumes indicated that ship emitted aerosol was substantially different from background aerosol: fresh ship exhaust was preferentially enriched in aerosol particles with diameters below 100nm and in black carbon particles with core diameters above 300-400nm. With the present work the impact of marine traffic on the concentration and properties of atmospheric components within the marine boundary layer over the open water of the Southern Baltic Sea is assessed with airborne observations for the first time. Due to the high uncertainty affecting the estimations of ship emissions, this dataset represents a valuable reference for the assessment of ship emission inventories and related environmental-climatic impacts on the Southern Baltic Sea.

Description: Aerosol particles impact the Arctic climate system both directly and indirectly by modifying cloud properties, yet our understanding of their vertical distribution, chemical composition, mixing state, and sources in the summertime Arctic is incomplete. In situ vertical observations of particle properties in the high Arctic combined with modelling analy- sis on source attribution are in short supply, particularly dur- ing summer. We thus use airborne measurements of aerosol particle composition to demonstrate the strong contrast be- tween particle sources and composition within and above the summertime Arctic boundary layer. In situ measure- ments from two complementary aerosol mass spectrometers, the Aircraft-based Laser Ablation Aerosol Mass Spectrom- eter (ALABAMA) and an Aerodyne high-resolution time- of-flight aerosol mass spectrometer (HR-ToF-AMS), are pre- sented alongside black carbon measurements from an single particle soot photometer (SP2). Particle composition anal- ysis was complemented by trace gas measurements, satel- lite data, and air mass history modelling to attribute parti- cle properties to particle origin and air mass source regions. Particle composition above the summertime Arctic bound- ary layer was dominated by chemically aged particles, con- taining elemental carbon, nitrate, ammonium, sulfate, and organic matter. From our analysis, we conclude that the pres- ence of these particles was driven by transport of aerosol and precursor gases from mid-latitudes to Arctic regions. Specifically, elevated concentrations of nitrate, ammonium, and organic matter coincided with time spent over vegeta- tion fires in northern Canada. In parallel, those particles were largely present in high CO environments (〉 90 ppbv ). Ad- ditionally, we observed that the organic-to-sulfate ratio was enhanced with increasing influence from these fires. Besides vegetation fires, particle sources in mid-latitudes further in- clude anthropogenic emissions in Europe, North America, and East Asia. The presence of particles in the Arctic lower free troposphere, particularly sulfate, correlated with time spent over populated and industrial areas in these regions. Further, the size distribution of free tropospheric particles containing elemental carbon and nitrate was shifted to larger diameters compared to particles present within the boundary layer. Moreover, our analysis suggests that organic matter, when present in the Arctic free troposphere, can partly be identified as low molecular weight dicarboxylic acids (ox- alic, malonic, and succinic acid). Particles containing dicar- boxylic acids were largely present when the residence time of air masses outside Arctic regions was high. In contrast particle composition within the marine boundary layer was largely driven by Arctic regional processes. Air mass history modelling demonstrated that alongside primary sea spray particles, marine biogenic sources contributed to secondary aerosol formation via trimethylamine, methanesulfonic acid, sulfate, and other organic species. Our findings improve our knowledge of mid-latitude and Arctic regional sources that influence the vertical distribution of particle chemical com- position and mixing state in the Arctic summer.