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Investigation results of a coarse and accumulation mode of aerosol properties above the Baltic Sea are reported. A most important role in the direct aerosol effect on climate have aerosols from the group of coarse and accumulation mode particles. Overseas in the atmosphere, there is a lot of aerosols from the fine fraction but their impact is not so important as coarse and accumulation mode particles. Sea spray emission from the sea surface takes place over a wide range of aerosol particle size distribution, it is also large in size range which are studying in this work ( Lewis and Schwartz, 2004 ). The discussed range is most important in view of atmospheric optical properties, smaller particles do not have such an influence on scattering as particles from range 0.5–2 µm. The research was performed with a multiwavelength lidar. Due to the application of special software, the aerosol particle size distributions were retrieved from the lidar returns. That provided an opportunity to determine the profiles of the aerosol effective radius. We showed that the aerosol properties depend mainly on the direction of the air mass advection and the wind speed. The impact of the Baltic Sea on the aerosol size distribution is huge in the case of the advection from the open sea. Moreover, the aerosol effective radiuses in the whole boundary layer are much larger in the case of strong than for light wind. Our results suggest that the aerosol flux and the aerosol particle size distribution should be related to the wind speed in the emission function.

Summary This study presents the preliminary results of combining underwater acoustic ambient noise measurements with those of in-situ sea spray fluxes (SSF). Hydroacoustic measurements (in the frequency range 80 Hz –12.5 kHz) were made using an underwater noise recording system developed at the Institute of Oceanology of the Polish Academy of Sciences which was then deployed in the southern Baltic Sea. The simultaneous measurements of coarse sea spray fluxes (with particle diameters ranging from 0.5 to 47 µm) were made on board the r/v Oceania using the gradient method. Observations were conducted for the duration of the passage of an atmospheric front that lasted 2.5 days (60 hours of measurements). There were significant differences in the sound pressure level (SPL) and aerosol fluxes observed between the first part of measurements (developing wave state) and the second part (developed waves). Wave parameters, such as peak period, significant wave height, wave age, and mean wave slope acquired from the WAM (WAve Model), were used to investigate the impact of wave field properties on noise and aerosol flux measurements. We observed different behaviours in the power spectrum density (PSD) levels of noise for these parameters depending on the wave state development.

The Poland-AOD aerosol research network was established in 2011 to improve aerosol–climate interaction knowledge and provide a real-time and historical, comprehensive, and quantitative database for the aerosol optical properties distribution over Poland. The network consists of research institutions and private owners operating 10 measurement stations and an organization responsible for aerosol model transport simulations. Poland-AOD collaboration provides observations of spectral aerosol optical depth (AOD), Ångstrom Exponent (AE), incoming shortwave (SW) and longwave (LW) radiation fluxes, vertical profiles of aerosol optical properties and surface aerosol scattering and absorption coefficient, as well as microphysical particle properties. Based on the radiative transfer model (RTM), the aerosol radiative forcing (ARF) and the heating rate are simulated. In addition, results from GEM-AQ and WRF-Chem models (e.g., aerosol mass mixing ratio and optical properties for several particle chemical components), and HYSPLIT back-trajectories are used to interpret the results of observation and to describe the 3D aerosol optical properties distribution. Results of Poland-AOD research indicate progressive improvement of air quality and at mospheric turbidity during the last decade. The AOD was reduced by about 0.02/10 yr (at 550 nm), which corresponds to positive trends in ARF. The estimated clear-sky ARF trend is 0.34 W/m2/10 yr and 0.68 W/m2/10 yr, respectively, at TOA and at Earth’s surface. Therefore, reduction in aerosol load observed in Poland can significantly contribute to climate warming.

Black carbon (BC) and Brown Carbon (BrC) absorbs sunlight and heat the atmosphere. The heating rate (HR) can be determined from the divergence of the net radiative flux with altitude (vertical profiles) or from the modelling activity; however, it determination is, up to now, too sparse, does not account for light-absorbing-aerosol (LAA) speciation and for the influence of different cloudy sky conditions on the BC induced heating rate (HR) in the atmospheric layer below clouds. This work applies a new method (Ferrero et al., 2018) to experimentally determine (at high time resolution) the HR induced by the LAA from mid-latidudes to the Arctic along two years (2018-2019, June-August) of oceanographic cruises moving from 54°N to 81°N and from 2°W to 25°E.The HR was experimentally determined at high time resolution and apportioned in the context of LAA species (BC, BrC), and sources (fossil fuel, FF; biomass burning, BB) as reported in Ferrero et al. (2018) equipping the Oceania vessel of the Polish Academy of Science with the following instrumentation:1) Aethalometer (AE-33, Magee Scientific, 7-λ), 2) Multiplexer-Radiometer-Irradiometer ROX (diffuse, direct and reflected radiance: 350-1000 nm, 1 nm resolution), 3) a SPN1 radiometer (global and diffuse radiation), 4) High volume sampler (TSP ECHO-PUF Tecora). Samples were analysed for ions (Dionex IC) and by EC/OC by using DRI Model 2015 Multi-Wavelength Thermal/Optical Carbon Analyzer. Radiometers were compensated for the ship pitch and roll by an automatic gimbal. AE33 absorption coefficient accuracy was determined through comparison with a MAAP (Thermo-Fischer).The HR showed a clear latitudinal behavior with higher values in the harbor of Gdansk (0.29±0.01 K/day) followed by the Baltic Sea (0.04±0.01 K/day), the Norvegian Sea (0.01±0.01 K/day) and finally with the lowest values in the pure Arctic Ocean (0.003±0.001 K/day).They followed the decrease of both BC concentrations and global radiation from 1189±21 ng/m3 and 230±6 W/m2 (Gdansk) to 27±1 ng/m3 and 111±3 W/m2 (Arctic Ocean). The latitunal gradient of the HR clearly demonstrate that the warming of the Arctic could be influenced by a heat transport. In this respect, the LAA added about 300 J/m3 at mid-latitudes and only 3 J/m3 close to the North Pole. Moreover, above the Arctic circle, 70% of the HR was due to the diffuse radiation induced by cloud presence, a condition that climate models in clear-sky assumption cannot capture. In addition, in the Arctic the BrC experienced an increase of 60% in determining the HR compared to mid-latitudes.Acknowledgements: GEMMA Center - Project MIUR – Dipartimenti di Eccellenza 2018–2022.Reference: Ferrero, L., et al (2018) Environ. Sci Tech., 52, 3546−3555

Summary This paper presents the results of a comparison of basic meteorological parameters in two Arctic fjords situated on the west coast of Spitsbergen, the main island of the Svalbard archipelago. Air temperature, wind speed and direction, humidity and cloud cover from the period 2005 to 2016 are described and compared with previous (from 1975) analyses of meteorological conditions in the investigated region. Such a choice of dates coincides with the time the GAME project measurements were carried out. The main goal of this study was to compare meteorological conditions in two fjords: Hornsund and Kongsfjorden, during the time of rapid climate changes. The results are collated with research results available in literature from previous years. We discovered that in the investigated period the climate of the Hornsund region is more oceanic than in Kongsfjorden. The stable level of the difference in climate elements is manifested and is evident mainly through greater amplitudes in air temperatures in Kongsfjorden, and in stronger winds in Hornsund.

Summary This paper presents the results of Aerosol Optical Depth (AOD) studies which took place in Ny-Alesund in the spring of 2014 during the iAREA campaign. The measurements were taken using Microtops II hand-held sunphotometers along the Kongsfjorden, on a path leading from the research village to the fjord opening. Local breeze circulation was observed during the measurement campaign which resulted in an evident increase of AOD along the measurement profile towards the open sea. Using the observed AOD, changes over the open sea have been calculated and the location of the breeze front has been determined.

Sea spray aerosol flux is an important element of sub-regional climate modeling. The majority of works related to this topic concentrate on open ocean research rather than on smaller, inland seas, e.g., the Baltic Sea. The Baltic Sea is one of the largest brackish inland seas by area, where major inflows of oceanic waters are rare. Furthermore, surface waves in the Baltic Sea have a relatively shorter lifespan in comparison with oceanic waves. Therefore, emission of sea spray aerosol may differ greatly from what is known from oceanic research and should be investigated. This article presents a comparison of sea spray aerosol measurements carried out on-board the s/y Oceania research ship with data calculated in accordance to the WAM model. The measurements were conducted in the southern region of the Baltic Sea during four scientific cruises. The gradient method was used to determinate aerosol fluxes. The fluxes were calculated for particles of diameter in range of 0.5–47 μm. The correlation between wind speed measured and simulated has a good agreement (correlation in range of 0.8). The comparison encompasses three different sea spray generation models. First, function proposed by Massel (2006) which is based only on wave parameters, such as significant wave height and peak frequency. Second, Callaghan (2013) which is based on Gong (2003) model (wind speed relation), and a thorough experimental analysis of whitecaps. Third, Petelski et al. (2014) which is based on in-situ gradient measurements with the function dependent on wind speed. The two first models which based on whitecaps analysis are insufficient. Moreover, the research shows strong relation between aerosol emission and wind speed history.

Studies of aerosol particle number concentration (PNC) level over open sea in the southern and south-eastern Baltic Sea regions were performed during five cruises (2005–2006, 2008–2010) by RV Oceania and at the coastal Preila station (Lithuania). A comparative analysis was performed of aerosol PNC variation at open sea versus measurements taken at the coastal site under various conditions (breaking waves, fog events, NPF), considering transport of forest fire products and advection of different air mass types to the investigation sites. It was found that the average PNC over the open sea (3000–4000 cm− 3) was generally higher than at the coastal site (2000–3000 cm− 3). Breaking waves caused by the latitudinal or longitudinal long-lasting (3–4 days) constant-direction wind under stormy conditions had the strongest effect on the aerosol PNC over the Baltic Sea. The aerosol PNC in the marine boundary layer (MBL) of the south-eastern Baltic Sea during fog did not depend on the air mass type over open sea, in contrast to the coastal site, that is, the average PNC level (3000–4000 cm− 3) in the MBL, which could be constantly affected by specific environmental factors as a source of condensation nuclei for the fog formation. Short-term increases of aerosol PNC in the MBL (5000–10,000 cm− 3) were higher than in the same periods of the time scale at the coastal site (3000–6000 cm− 3) during NPF events, and therefore the open sea environment may facilitate a more favourable condition for the NPF, that is, exhaust and biogenic emissions from ships and the marine environment.

We analysed δ13C of total carbon (TC) and δ15N of total nitrogen (TN) in submicron (PM1) and size segregated aerosol particles (PM0.056–2.5) collected during a cruise in the Baltic Sea from 9 to 17 November 2012. PM1 were characterized by the highest δ13C (–26.4‰) and lowest δ15N (–0.2 and 0.8‰) values when air masses arrived from the southwest direction (Poland). The obtained δ13C values indicated that combined emissions of coal and diesel/gasoline combustion were the most likely sources of TC. The depleted δ15N values indicated that TN originated mainly from liquid fuel combustion (road traffic, shipping) during this period. The lowest δ13C and highest δ15N values were determined in PM1 samples during the western airflow when the air masses had no recent contact with land. The highest δ15N values were probably associated with chemical aging of nitrogenous species during long-range transport, the lowest δ13C values could be related to emissions from diesel/gasoline combustion, potentially from ship traffic. The δ13C analysis of size-segregated aerosol particles PM0.056–2.5 revealed that the lowest δ13C values were observed in the size range from 0.056 to 0.18 µm and gradual 13C enrichment occurred in the size range from 0.18 to 2.5 µm due to different sources or formation mechanisms of the aerosols.

This paper is focused on Saharan dust transport to Central Europe/Poland; we compare properties of atmospheric Saharan dust using data from NAAPS, MACC, AERONET as well as observations obtained during HyMountEcos campaign in June 2012. Ten years of dust climatology shows that long-range transport of Saharan dust to Central Europe is mostly during spring and summer. HYSPLIT back-trajectories indicate airmass transport mainly in November, but it does not agree with modeled maxima of dust optical depth. NAAPS model shows maximum of dust optical depth (~0.04–0.05, 550 nm) in April–May, but the MACC modeled peak is broader (~0.04). During occurrence of mineral dust over Central-Europe for 14% (NAAPS) / 12% (MACC) of days dust optical depths are above 0.05 and during 4% (NAAPS) / 2.5% (MACC) of days dust optical depths exceed 0.1. The HyMountEcos campaign took place in June–July 2012 in the mountainous region of Karkonosze. The analysis includes remote sensing data from lidars, sunphotometers, and numerical simulations from NAAPS, MACC, DREAM8b models. Comparison of simulations with observations demonstrates the ability of models to reasonably reproduce aerosol vertical distributions and their temporal variability. However, significant differences between simulated and measured AODs were found. The best agreement was achieved for MACC model.

The subject of this study is to use in-situ measurements, passive and active remote sensing observations, as well as numerical simulations to describe the temporal variability of aerosol single-scattering properties such as aerosol optical depth (AOD), single scattering albedo (SSA), and aerosol direct shortwave forcing at the Earth׳s surface during the transport of biomass burning (BB) aerosols from Canada to Europe between 2nd and 7th of July 2013. According to the MODIS observations made in the IR spectrum, an area of over 200,000 km 2 was affected by the BB during the episode. Regarding the AERONET data in Canada, results show a significant variability of AOD within the whole period with a special enhancement between 6th and 9th July, when AOD anomaly led to an increase up to 1.5 (500 nm). Low-values of SSA reported at Yellowknife Aurora and Waskesiu are likely to be due to flaming combustion from closely located source areas. MODIS and CALIPSO observations, as well as numerical simulations of the NAAPS model, show transport of smoke particles over the Northern Atlantic Ocean and further eastward. Indeed, the event was observed at a different times and locations over Europe between 2nd and 14th July. During that period a number of AERONET stations, mainly located close to the Baltic Sea reported AOD at 500 nm of above 1. Compared to Canada the SSA in Europe was higher, indicating particle transformation over the Atlantic Ocean. Lidar observations in the northern Poland showed aerosol layers occurring between PBL height and tropopause with a significant (up to 55%) contribution to the total AOD. However, lidar measurements in Central Poland (Warsaw and Belsk) indicate that aerosols were confined mainly in the middle and lower troposphere. A diurnal mean aerosol direct radiative forcing estimated at the ground level during the event was below −30 W/m 2 with radiative forcing efficiency between −60 and −100 W/m 2 /τ 500. The strongest efficiency was found at the Strzyzow station, which was caused by further air mass transformation during its transport over Poland.

This paper presents the results of measurements of aerosol physical and chemical properties during iAREA2014 campaign that took place on Svalbard between 15th of Mar and 4th of May 2014. With respect to field area, the experiment consisted of two sites: NyeAlesund (78�550N, 11�560E) and Longyearbyen (78�130N, 15�330E) with further integration of Aerosol Robotic Network (AERONET) station in Hornsund (77�000N, 15�330E). The subject of this study is to investigate the inesitu, passive and active remote sensing observations as well as numerical simulations to describe the temporal variability of aerosol singleescattering properties during spring season on Spitsbergen. The retrieval of the data indicates several event days with enhanced singleescattering properties due to the existence of sulphate and additional seaesalt load in the atmosphere which is possibly caused by relatively high wind speed. Optical results were confirmed by numerical simulations made by the GEMeAQ model and by chemical observations that indicated up to 45% contribution of the seaesalt to a PM10 total aerosol mass concentration. An agreement between the in-situ optical and microphysical properties was found, namely: the positive correlation between aerosol scattering coefficient measured by the nephelometer and effective radius obtained from laser aerosol spectrometer as well as negative correlation between aerosol scattering coefficient and the Angstrom exponent indicated that slightly larger particles dominated during special events. The inesitu surface observations do not show any significant enhancement of the absorption coefficient as well as the black carbon concentration which might occur during spring. All of extensive singleescattering properties indicate a diurnal cycle in Longyearbyen, where 21:00e5:00 data stays at the background level, however increasing during the day by the factor of 3e4. It is considered to be highly connected with local emissions originating in combustion, traffic and harbour activities. On the other hand, no daily fluctuations in NyeAlesund are observed. Mean values in NyeAlesund are equal to 8.2, 0.8 Mm�1 and 103 ng/m3 for scattering, absorption coefficients and black carbon concentration; however in Longyearbyen (only data from 21:00e05:00 UTC) they reach 7.9, 0.6 Mm�1 as well as 83 ng/ m3 respectively. Overall, the spring 2014 was considerably clean and seaesalt was the major aerosol component

In this paper we describe the results of a research campaign dedicated to the studies of aerosol optical properties in different regions of both the open Baltic Sea and its coastal areas. During the campaign we carried out simultaneous measurements of aerosol optical depth at 4 stations with the use of the hand-held Microtops II sun photometers. The studies were complemented with aerosol data provided by the MODIS. In order to obtain the full picture of aerosol situation over the study area, we added to our analyses the air mass back-trajectories at various altitudes as well as wind fields. Such complex information facilitated proper conclusions regarding aerosol optical depth and Angstrom exponent for the four locations and discussion of the changes of aerosol properties with distance and with changes of meteorological factors. We also show that the Microtops II sun photometers are reliable instruments for field campaigns. They are easy to operate and provide good quality results.

This work provides information on selected optical parameters related to volcanic ash produced during the eruption of the Eyjafjoll volcano in Iceland in 2010. The observations were made between 16 and 18 April 2010 at four stations representative for northern (Sopot), central (Warsaw, Belsk) and south-eastern (Strzyzow) regions of Poland. The largest ash plume (in terms of aerosol optical thickness) over Poland was observed at night of 16/17 April 2010 in the layer between 4 and 5.5 km a.s.l. The highest values of the aerosol extinction coefficient reached 0.06e0.08 km � 1 at 532 nm (based on lidar observations in Warsaw) and 0.02e0.04 km � 1 at 1064 nm (based on ceilometer observations in Warsaw). The corresponding optical thickness due to volcanic ash reached values of about 0.05 at 532 nm and about 0.03 at 1064 nm. These values are similar to those reported for the Belsk station based on lidar observations. The ash mass concentration estimated based on the maximum aerosol extinction coefficient reached 0.22 � 0.11 mg m � 3 . This value is significantly lower than the limit (2 mg m � 3 ) for the aircraft operation.

This paper presents the results of the studies of aerosol optical properties measured using lidars and sun photometers. We describe two case studies of the combined measurements made in two coastal zones in Crete in 2006 and in Rozewie on the Baltic Sea in 2009. The combination of lidar and sun photometer measurements provides comprehensive information on both the total aerosol optical thickness in the entire atmosphere as well as the vertical structure of aerosol optical properties. Combination of such information with air mass back-trajectories and data collected at stations located on the route of air masses provides complete picture of the aerosol variations in the study area both vertically and horizontally. We show that such combined studies are especially important in the coastal areas where depending on air mass advection directions and altitudes the influence of fine or coarse mode (in this case possibly sea-salt) particles on the vertical structure of aerosol optical properties is an important issue to consider.

This paper presents the measurements of a vertical structure of aerosol optical properties performed during the MACRON (Maritime Aerosol, Clouds and Radiation Observation in Norway) campaign, which took place in July and August 2007 at ALOMAR observatory on Andoya island (69.279°N, 16.009°E, elevation 380 m a.s.l.). The mean value of the aerosol optical thickness (AOT) at 500 nm during campaign was 0.12. Significant increase of the AOT above longtime mean value was observed on 7 and 8 August 2007 when the AOT exceeded 0.4 at 500 nm. Analyses of back trajectories show the aerosol transported from over Africa and Central Europe. The aerosol extinction coefficient obtained from the synergy of ceilometer and sun photometer observations reached 0.05-0.08 km –1 (at 1064 nm) in the dust layer. The single scattering

New particle formation and growth were observed at a coastal site (Preila station, Lithuania) during 1997 and 2000-2002. The total amountof data analysed covers 291 one-day periods, 45 (15%) of which were long-term, new particle formation days. Short-term nucleationevents (from a few minutes to one hour) and long-term events (from one to eight hours) were identified. The mean particlegrowth rate, condensation sink and condensable vapour source rate during nucleation events were 3.9 nm h-1, 1.45 × 10-3 cm-3 s-1 and 7.5 × 104 cm-3 s-1 respectively.The average formation rate J10 was 0.4 cm-3 s-1. The nucleation events were accompaniedmainly by air masses transported from the north (43%) and north-west (19%). Meteorological parameters and trace gas (O3, SO2,NO2) concentrations were also analysed. It was found that nucleation events are related to high levels of solar radiation.

In this paper, spectra of aerosol optical thickness from the AERONET (AErosol RObotic NETwork) station at Hornsund in the southern part of Spitsbergen were employed to study the impact of air mass history on aerosol optical thickness for wavelength λ=500 nm – AOT(500) – and the Ångström exponent. Backward trajectories computed, using the NOAA HYSPLIT model, were used to trace air history. It was found that in spring, the changes in AOT values over the Hornsund station were strongly influenced by air mass trajectories 8 days or longer in duration, arriving both in the free troposphere and at an altitude of 1 km above sea level. Nevertheless, free tropospheric advection was dominant. AOT variability in summer was best explained by the local direction and speed of advection (1-day trajectories) and was dominated by the effectiveness of cleansing processes. During the ASTAR 2007 campaign, the aerosols near Hornsund displayed low AOT values ranging from 0.06 to 0.09, which is lower than the mean AOT(500) for spring seasons from 2005 to 2007 (0.110±0.007; mean ± standard deviation of mean). 9 April 2007 with AOT(500)=0.147 was exceptional. The back-trajectories belonged to clusters with low and average cluster mean AOT. Apart from the maximum AOT of 9 April 2007, the observed AOT values were close to or lower than the means for the clusters to which they belonged.

In this work multi wavelength Raman lidar data from Ny-Ålesund, Spitsbergen have been analysed for the spring 2014 Arctic haze season, as part of the iAREA campaign. Typical values and probability distributions for aerosol backscatter, extinction and depolarisation, the lidar ratio and the color ratio for 4 different altitude intervals within the troposphere are given. These quantities and their dependencies are analysed and the frequency of altitude-dependent observed aerosol events are given. A comparison with ground-based size distribution and chemical composition is performed. Hence the aim of this paper is to provide typical and statistically meaningful properties of Arctic aerosol, which may be used in climate models or to constrain the radiative forcing. We have found that the 2014 season was only moderately polluted with Arctic haze and that sea salt and sulphate were the most dominant aerosol species. Moreover the drying of an aerosol layer after cloud disintegration has been observed. Hardly any clear temporal evolution over the 4 week data set on Arctic haze is obvious with the exception of the extinction coefficient and the lidar ratio, which significantly decreased below 2 km altitude by end April. In altitudes between 2 and 5 km the haze season lasted longer and the aerosol properties were generally more homogeneous than closer to the surface. Above 5 km only few particles were found. The variability of the lidar ratio is discussed. It was found that knowledge of the aerosol’s size and shape does not determine the lidar ratio. Contrary to shape and lidar ratio, there is a clear correlation between size and backscatter: larger particles show a higher backscatter coefficient.

This paper presents the data obtained during the polar research cruises of the r/v Oceania in 1995–2001. The aerosol size distributions were measured using the laser particle counter CSASP-100-HV-SP. The size spectral density between diameters 0.5–15 μ m was found to fit the following form: dN/dr = n(2 r) = exp (a2 r + b) , where: a = − 0.29 and b are functions of wind speed. Additionally, poor precision of the sea spray emission determination using only the aerosol concentration data measured at one altitude was confirmed.

Sea spray emission fluxes were calculated on the basis of vertical gradients of the aerosol concentration from experimental data collected with a laser particle counter during two polar scientific cruises carried out in July and August 2000 and 2001, and during cruises in the Baltic Sea in October 2000, and May and October 2001. Calculated fluxes range between 103 and 10 7 m −2 s −1 .

In this work we present the annual changes of two major, climate related aerosol optical parameters measured at three Spitsbergen locations, Ny-Alesund, Longyearbyen and Hornsund over a period between 2000 and 2012. We discuss the changes of aerosol optical depth (AOD) at 500 nm and the Angstrom exponent (AE) (440–870 nm) measured with use of different types of sun photometers. For the measurement data we adopted several data quality assurance techniques and the calibration of the instruments was taken into consideration. The results obtained show that marine source has been a dominating of aerosol sources over Spitsbergen. Some years (2005, 2006, 2008 and 2011) show very high values of AOD due to strong aerosol events such as the Arctic Haze. In general the mean AOD values increase over the period of 2000 and 2012 over Spitsbergen. This may indicate the presence of larger scale of atmospheric pollution in the region.

Multi-year sets of ground-based sun-photometer measurements conducted at 12 Arctic sites and 9 Antarctic sites were examined to determine daily mean values of aerosol optical thickness tau(lambda) at visible and near-infrared wavelengths, from which best-fit values of Angstrom's exponent alpha were calculated. Analyzing these data, the monthly mean values of tau(0.50 micrometers) and alpha and the relative frequency histograms of the daily mean values of both parameters were determined for winter-spring and summer-autumn in the Arctic and for austral summer in Antarctica. The Arctic and Antarctic covariance plots of the seasonal median values of alpha versus tau(0.50 micrometers) showed: (i) a considerable increase in tau(0.50 micrometers) for the Arctic aerosol from summer to winter-spring, without marked changes in alpha; and (ii) a marked increase in tau(0.50 micrometer) passing from the Antarctic Plateau to coastal sites, whereas alpha decreased considerably due to the larger fraction of sea-salt aerosol. Good agreement was found when comparing ground-based sun-photometer measurements of tau(lambda) and alpha at Arctic and Antarctic coastal sites with Microtops measurements conducted during numerous AERONET/MAN cruises from 2006 to 2013 in three Arctic Ocean sectors and in coastal and off-shore regions of the Southern Atlantic, Pacific, and Indian Oceans, and the Antarctic Peninsula. Lidar measurements were also examined to characterize vertical profiles of the aerosol backscattering coefficient measured throughout the year at Ny-Alesund. Satellite-based MODIS, MISR, and AATSR retrievals of tau(lambda) over large parts of the oceanic polar regions during spring and summer were in close agreement with ship-borne and coastal ground-based sun-photometer measurements. An overview of the chemical composition of mode particles is also presented, based on in-situ measurements at Arctic and Antarctic sites. Fourteen log-normal aerosol number size-distributions were defined to represent the average features of nuclei, accumulation and coarse mode particles for Arctic haze, summer background aerosol, Asian dust and boreal forest fire smoke, and for various background austral summer aerosol types at coastal and high-altitude Antarctic sites. The main columnar aerosol optical characteristics were determined for all 14 particle modes, based on in-situ measurements of the scattering and absorption coefficients. Diurnally averaged direct aerosol-induced radiative forcing and efficiency were calculated for a set of multimodal aerosol extinction models, using various Bidirectional Reflectance Distribution Function models over vegetation-covered, oceanic and snow-covered surfaces. These gave a reliable measure of the pronounced effects of aerosols on the radiation balance of the surface-atmosphere system over polar regions.

Properties of atmospheric aerosols and solar radiation reaching the Earth’s surface were measured during Summer 2011 in Sopot, Poland. Three cloudless days, characterized by different directions of incoming air-flows, which are typical transport pathways to Sopot, were used to estimate a radiative forcing due to aerosols present in each air mass.

Multiwavelength micropulse lidar (MML) designed for continuous optical sounding of the atmosphere is presented. A specific signal processing technique applying two directional Kalman filtering is introduced in order to enhance signal to noise ratio. Application of this technique is illustrated with profiles collected in course of COAST 2009 and WRNP 2010 research campaigns.

Material fluxes in the Arctic and Antarctic have been, in several respects, strongly affected recently. For example, atmospheric turbidity conditions are frequently subject to strong changes due to haze and dust transport episodes, which can cause considerable perturbations in the radiation balance of the atmosphere beyond regional scale. This, directly or indirectly, contributes to the increased mercury deposition and organic matter fluxes to sediments.The results show that local emissions are not always the most important factors influencing the composition of aerosol in the atmosphere of the west Spitsbergen region. The direct radiative impact of polar aerosols on the surface and at the top of the atmosphere (TOA) need to be studied more closely through both theoretical studies on the aerosol radiative properties and measurements of the surface reflectance characteristics.Mercury dissolved/solid partitioning, both in the unconsolidated, fluffy layer of suspended matter covering the sediments, and the uppermost sediment layer, indicate that the influence of the athmospheric mercury deposition event (AMDE) can prolong well into summer (July/August), and can provide a pathway to the food chain for mercury contained in sediments.Since terrigenous supplies of organic carbon to the Barents Sea are minor (∼5%) compared to the marine supply, modern sediment deposits in this region sequester on average 6.0 g/m2year organic carbon, or 5.8% of the annual integrated pelagic primary production. This burial fraction exceeds, by a factor of 3, the burial fraction derived for the Holocene.

Accuracy requirements for aerosol optical depth (AOD) in polar regions are much more stringent tan those usually encountered in established sun photometer networks, while comparability of data from different archive centres is a further important issue. Therefore, two intercomparison campaigns were held during spring 2006 at Ny-Ålesund (Svalbard) and autumn 2008 at Izaña (Tenerife) within the framework of the IPY POLAR-AOD project, with the participation of various research institutions routinely employing different instrument models at Arctic and Antarctic stations. As reported here, a common algorithm was used for data analysis with the aim of minimizing a large part of the discrepancies affecting the previous studies. During the Ny-Ålesund campaign, spectral values of AOD derived from measurements taken with different instruments were found to agree, presenting at both 500 nm and 870 nm wavelengths average values of root mean square difference (RMSD) and standard deviation of the difference (SDD) equal to 0.003. Correspondingly, the mean bias difference (MBD) varied mainly between _0.003 and þ0.003 at 500 nm, and between _0.004 and þ0.003 at 870 nm. During the Izaña campaign, which was also intended as an intercalibration opportunity, RMSD and SDD values were estimated to be equal to 0.002 for both channels on average, with MBD ranging between _0.004 and þ0.004 at 500 nm and between _0.002 and þ0.003 at 870 nm. RMSD and SDD values for Ångström exponent a were estimated equal to 0.06 during the Ny-Ålesund campaign and 0.39 at Izaña. The results confirmed that sun photometry is a valid technique for aerosol monitoring in the pristine atmospheric turbidity conditions usually observed at high latitudes. The Italian research activity was supported by the Programma Nazionale di Ricerche in Antartide (PNRA) and developed as a part of Subproject 2006/6.01: “POLAR-AOD: a network to characterize the means, variability and trends of the climate-forcing properties of aerosols in polar regions”. The GOA-UVA group was funded by MICINN under projects CGL2008-05939-C01/CLI, CGL2009-09740 and CGL2009-09480-E. The Canadian research activity was supported by CANDAC (Canadian Network for the Detection of Atmospheric Change) and their funding organizations: CFCAS (Canadian Foundation for Climate and Atmospheric Sciences, CFI (Canadian Foundation for Innovation), NSERC (National Sciences and Engineering Research Council) and the IPY (NSERC administered) fund. Polish efforts were made within a framework of the POLAR-AOD National Grant.

Large sets of filtered actinometer, filtered pyrheliometer and Sun photometer measurements have been carried out over the past 30 years by various groups at different Arctic and Antarctic sites and for different time periods. They were examined to estimate ensemble average, long-term trends of the summer background aerosol optical depth AOD(500 nm) in the polar regions ( omitting the data influenced by Arctic haze and volcanic eruptions). The trend for the Arctic was estimated to be between -1.6% and -2.0% per year over 30 years, depending on location. No significant trend was observed for Antarctica. The time patterns of AOD( 500 nm) and angstrom ngstrom's parameters a and beta measured with Sun photometers during the last 20 years at various Arctic and Antarctic sites are also presented. They give a measure of the large variations of these parameters due to El Chichon, Pinatubo, and Cerro Hudson volcanic particles, Arctic haze episodes most frequent in winter and spring, and the transport of Asian dust and boreal smokes to the Arctic region. Evidence is also shown of marked differences between the aerosol optical parameters measured at coastal and high-altitude sites in Antarctica. In situ optical and chemical composition parameters of aerosol particles measured at Arctic and Antarctic sites are also examined to achieve more complete information on the multimodal size distribution shape parameters and their radiative properties. A characterization of aerosol radiative parameters is also defined by plotting the daily mean values of a as a function of AOD( 500 nm), separately for the two polar regions, allowing the identification of different clusters related to fifteen aerosol classes, for which the spectral values of complex refractive index and single scattering albedo were evaluated.

[1] Sea spray emission fluxes were calculated on the basis of vertical gradients of the aerosol concentration data collected with a laser particle counter during four polar scientific cruises carried out in the summers of 2000, 2001, 2002, and 2003. The calculated flux values are the first obtained with a gradient method from data measured on the open ocean; such a method has a much better physical basis than any involving calculating fluxes from concentrations measured at one level only. The sea spray generation function we obtained was compared with other functions from the literature. We show that most literature sea spray generation functions are underestimated for the 1–8 μm radius range, some of them by a factor of 6.

[1] Vertical aerosol flux values collected in the marine atmospheric boundary layer during Baltic cruises of the R/V Oceania have been analyzed. It has been determined that the aerosol emission from the sea surface in the open Baltic is proportional to the average energy dissipation rate raised to the 2/3 power. A similar relationship has been derived using dimensional analysis and a simple model of aerosol emission. It has been demonstrated that aerosol emission from the open Baltic may be parameterized using significant wave height and wind velocity.

[1] Digital photographs of the sea surface were analyzed for the fraction of aerial coverage by whitecaps (stage A and B) in the north polar region of the Atlantic. Photography was accompanied by measurements of wind velocity, air temperature and humidity, sea surface temperature, and observations of significant wave height. Whitecap coverage increased significantly with an increase in wind speed (or wind friction velocity). Our data exhibit lower values of the average whitecap coverage at low and moderate wind speeds than previous estimates from literature. In addition, our results indicate that the prediction of whitecap coverage can be improved if the state of the development of surface waves is taken into account. Changes in sea surface temperature (2 to 13°C) and near-water air stability showed no discernible effect on whitecap coverage at any given wind speed within our data set.