Marine Aerosol Concentrations Research Articles

Mass and number concentration distribution of marine aerosol in the Western Pacific and the influence of continental transport

We quantify for the first time marine aerosol properties and their differences in the offshore and remote ocean in the mid-latitude South Asian waters, low-latitude South Asian waters, and equatorial waters of the Western Pacific Ocean, based on shipboard cruise observations conducted by the Western Pacific Ocean Scientific Observation Network in winter 2018, and further investigate the effects of long-range transport of continental aerosols on the marine environment. During the overall observation period, the average number concentration of particle matter which aerodynamic diameters<2.5 μm (PM2.5N) was 35.1 ± 87.4 cm−3 and the mass concentration (PM2.5M) was 12.3 ± 9.1 μg/m3. The PM2.5N and PM2.5M during the continental air mass transport period were 7.2 and 1.3 times higher than those during the non-transport period (109.2 ± 169.3 cm−3, 15.9 ± 14.9 μg/m3), respectively. Excluding transport period, the average PM2.5N and PM2.5M are reduced by 120% and 7%. Coarse mode particle number concentration (PM2.5–10N) and mass concentration (PM2.5–10M) are not significantly influenced by continental air masses (only a reduction of 7% and 2%). The variation of marine aerosol concentrations in different latitudes zones is greatly influenced by continental aerosol transport. The offshore PM2.5M/PM10M was 30%, 21%, and 22% in the mid-latitude sea of South Asia, a low-latitude sea of South Asia, and the equatorial sea, respectively. In comparison, in the remote ocean, the distribution ratio of PM2.5M/PM10M tended to be steady (22%–23%), and the background characteristics of marine aerosols were clearly represented. The aerosol concentration decreases with the increase of wind speed during the transport period, and the wind speed reflects the scavenging effect on aerosol. In the non-transport period, the wind speed at the sea surface promotes the generation of marine aerosols, and the impact in wind speed is strongest in the PM2.5–PM5 particle size range.

Aerosol characterization in an oceanic context around Reunion Island (AEROMARINE field campaign)

This article presents the results of the AEROMARINE field campaign which took place between February and April 2019 off the coast of Reunion Island in the South West Indian Ocean basin. The Southern Indian Ocean is of major interest for the study of marine aerosols, their distribution and variability. Six instrumented light plane flights and a ground-based microwave radiometer were used during the field campaign. These measurements were compared with the long-term measurements of the AERONET sun-photometer (based in St Denis, Reunion Island) and various instruments of the high altitude Maïdo Observatory (2.2 km above sea level, Reunion Island). These results were also analyzed using different model outputs: (i) the AROME mesoscale weather forecast model to work on the thermodynamics of the boundary layer, (ii) the FLEXPART-AROME Lagrangian particle dispersion model to assess the geographical and vertical origin of air masses, and (iii) the chemical transport model CAMS (Copernicus Atmosphere Monitoring Service) to work on the aerosol chemical composition of air masses. This allowed to highlight two points: (1) the atmospheric layer above 1.5 km is mainly composed of aerosols from the regional background; (2) the local environment (ocean or island) has little impact on the measured concentrations. Marine aerosols emitted locally are mostly measured below 0.5 km. The daytime marine aerosol distributions in the free troposphere measured by the aircraft were compared to the night-time aerosol distributions measured at the high altitude Maïdo Observatory when the Observatory is located in the free troposphere. The results indicate that this high altitude site of measurements is representative of the marine aerosol concentrations in the free troposphere. We also found that the CAMS reanalyses overestimated the aerosol optical depth in this region. Finally, our study strongly suggests that the AERONET station in St Denis (Reunion Island) can be considered as a representative marine station under the Tropics.

Linking marine phytoplankton emissions, meteorological processes, and downwind particle properties with FLEXPART

Abstract. Marine biogenic particle contributions to atmospheric aerosol concentrations are not well understood though they are important for determining cloud optical and cloud-nucleating properties. Here we examine the relationship between marine aerosol measurements (with satellites and model fields of ocean biology) and meteorological variables during the North Atlantic Aerosols and Marine Ecosystems Study (NAAMES). NAAMES consisted of four field campaigns between November 2015 and April 2018 that aligned with the four major phases of the annual phytoplankton bloom cycle. The FLEXible PARTicle (FLEXPART) Lagrangian particle dispersion model is used to spatiotemporally connect these variables to ship-based aerosol and dimethyl sulfide (DMS) observations. We find that correlations between some aerosol measurements with satellite-measured and modeled variables increase with increasing trajectory length, indicating that biological and meteorological processes over the air mass history are influential for measured particle properties and that using only spatially coincident data would miss correlative connections that are lagged in time. In particular, the marine non-refractory organic aerosol mass correlates with modeled marine net primary production when weighted by 5 d air mass trajectory residence time (r=0.62). This result indicates that non-refractory organic aerosol mass is influenced by biogenic volatile organic compound (VOC) emissions that are typically produced through bacterial degradation of dissolved organic matter, zooplankton grazing on marine phytoplankton, and as a by-product of photosynthesis by phytoplankton stocks during advection into the region. This is further supported by the correlation of non-refractory organic mass with 2 d residence-time-weighted chlorophyll a (r=0.39), a proxy for phytoplankton abundance, and 5 d residence-time-weighted downward shortwave forcing (r=0.58), a requirement for photosynthesis. In contrast, DMS (formed through biological processes in the seawater) and primary marine aerosol (PMA) concentrations showed better correlations with explanatory biological and meteorological variables weighted with shorter air mass residence times, which reflects their localized origin as primary emissions. Aerosol submicron number and mass negatively correlate with sea surface wind speed. The negative correlation is attributed to enhanced PMA concentrations under higher wind speed conditions. We hypothesized that the elevated total particle surface area associated with high PMA concentrations leads to enhanced rates of condensation of VOC oxidation products onto PMA. Given the high deposition velocity of PMA relative to submicron aerosol, PMA can limit the accumulation of secondary aerosol mass. This study provides observational evidence for connections between marine aerosols and underlying ocean biology through complex secondary formation processes, emphasizing the need to consider air mass history in future analyses.

ГИДРОХИМИЧЕСКИЙ СОСТАВ И РЕДКОЗЕМЕЛЬНЫЕ ЭЛЕМЕНТЫ В ПОЛИГОНАЛЬНО-ЖИЛЬНЫХ ЛЬДАХ КЛЮЧЕВЫХ РАЙОНОВ КРИОЛИТОЗОНЫ КАРСКОГО РЕГИОНА

Актуальность исследования. Информация о составе, льдистости и геохимических особенностях мерзлых пород необходима при освоении нефтегазоконденсатных месторождений Ямала, Гыдана и Таймыра. Среди факторов, определяющих экологию тундровых ландшафтов криолитозоны, большое значение имеют подземные льды, в том числе полигонально-жильные, и последствия их вытаивания. Гидрохимический состав и содержание редкоземельных элементов в сингенетических жилах фиксируют информацию об источниках влаги и условиях, при которых происходило их формирование. Соотношение основных ионов и распределение редкоземельных элементов в растворе может быть использовано для оценки влияния на состав льда атмосферных осадков, морских и вулканических аэрозолей, антропогенного загрязнения. Цель: выявить источники поступления химических элементов и оценить влияние типа льдовыделения на гидрохимический состав и распределение редкоземельных элементов в различных генетических типах льда – полигонально-жильном, морском, озерном и фирновом льдах. Объекты: полигонально-жильный лед, вмещающие его отложения, сезонные льды, поверхностные воды, отобранные в экспедициях ИКЗ ТюмНЦ СО РАН в 2009–2014 гг. Методы исследования химического состава: масс-спектрометрия с индуктивно связанной плазмой, атомно-абсорбционная спектрометрия, эмиссионная фотометрия, хроматография. Результаты. Установлено, что на химический состав полигонально-жильных льдов, изученных в прибрежной зоне ключевых участков о. Белый, о. Сибирякова, Западного Ямала и Западного Таймыра, имели влияние морские и континентальные аэрозоли. Сингенетические полигонально-жильные льды, пресные и ультрапресные по минерализации, сформированы при промерзании талых вод, которые содержат сорбированные снегом морские аэрозоли – взвешенные в атмосфере твердые и жидкие частицы. Полигонально-жильные льды в удаленном от моря районе оз. Сохонто не имеют признаков морского влияния по соотношению основных ионов. Полигонально-жильные льды с минеральными включениями формировались не только за счет талых снеговых вод с аэрозолями континентального происхождения, но и за счет надмерзлотных вод. В полигонально-жильных льдах выявлено увеличение содержаний лантаноидов в водорастворимой форме по сравнению с кларковыми значениями и современными поверхностными льдами. По цериевой аномалии в большинстве изученных сингенетических ледяных жил подтверждается участие морских аэрозолей. По распределениям редкоземельных элементов выявлено характерное для полигонально-жильных льдов соотношение легких и тяжелых редкоземельных элементов равное 0,9, и соотношение лантана к остальным лантаноидам, равное 0,2. Морской лед наследует минерализацию и состав морской воды. Озерный лед различается по глубине и отражает сезонное изменение гидрохимического состава при ледоставе и повышение концентрации морских аэрозолей в снеге, перекрывающем озерный лед. Фирновый лед полярного Урала имеет очень низкую минерализацию, в нем отсутствуют примеси морского аэрозоля. В полигонально-жильных льдах голоценового и неоплейстоценового возраста реализован природный механизм накопления редкоземельных элементов в водорастворимой форме в комплексе с железом, торием и иттрием. Вытаивание ледяных жил может приводить к поступлению редкоземельных элементов в поверхностные воды.

Molecular marker study of aerosols in the northern South China Sea: Impact of atmospheric outflow from the Indo-China Peninsula and South China

Continental outflow influences concentration and chemical composition of marine aerosols, which has an important impact on regional biogeochemistry and climate. Aerosols sampling for molecular marker study was conducted from June 2015 to May 2016 at Xieyang Island in the northern South China Sea (SCS), to learn the impact of outflow from Indo-China Peninsular (ICP) and South China (SC). Xieyang Island was under the influence of air masses from ICP and SC nearly 70% of the year. Levels of anhydrosugars were higher during October to early March. They were lower in April and May, although biomass burning events in ICP were most intensive and half of air masses back trajectories passed through ICP in this period. Significant correlations between levels of anhydrosugars, polycyclic aromatic hydrocarbons, n-alkanes, high molecular weight n-fatty acids and terephthalic acid were observed, suggesting co-emissions of these compounds. Source types of aerosol primary organic matter (POM) tracked by these markers, namely open burning of municipal wastes, fossil fuel combustion, higher plant emissions and biomass burning, largely contributed in fall and winter with SC to be an important source region. However, levels of sugar alcohols (a group of biogenic aerosol tracers) were higher in warm seasons with ICP and SCS to be the main source regions, and were poorly correlated with levels of other molecular markers. Carbon preference index of n-alkanes also increased in warm seasons, indicating enhanced higher plant wax emissions. It suggested that there was a close link between biogenic emissions of sugar alcohols (or n-alkanes) and the growing activities of related organisms. Besides continental outflow, there were marine sources of steranes, hopanes (fossil sources tracers) and mannitol (a sugar alcohol), since their levels were higher for aerosol samples basically influenced by air masses originated from SCS.

A 125-year record of climate and chemistry variability at the Pine Island Glacier ice divide, Antarctica

Abstract. The Mount Johns (MJ) ice core (79°55′ S; 94°23′ W) was drilled near the Pine Island Glacier ice divide on the West Antarctic Ice Sheet during the 2008–2009 austral summer, to a depth of 92.26 m. The upper 45 m of the record covers approximately 125 years (1883–2008), showing marked seasonal variability. Trace element concentrations in 2137 samples were determined using inductively coupled plasma mass spectrometry. In this study, we reconstruct mineral dust and sea salt aerosol transport and investigate the influence of climate variables on the elemental concentrations at the MJ site. The ice core record reflects changes in emissions as well as atmospheric circulation and transport processes. Our trajectory analysis shows distinct seasonality, with strong westerly transport in the winter months and secondary northeasterly transport in the summer. During summer months, the trajectories present slow-moving (short) transport and are more locally influenced than in other seasons. Finally, our reanalysis correlations with trace element suggest that marine-derived trace element concentrations are strongly influenced by sea ice concentration and sea surface temperature anomalies. The results show that seasonal elemental concentration maxima in sea salt elements correlate well with the sea ice concentration winter maxima in the west Amundsen and Ross seas. Lastly, we observed an increased concentration of marine aerosols when sea surface temperature decreased.

Influence of the Surf Zone on the Marine Aerosol Concentration in a Coastal Area

Svensson [Found. Phys. 45, 1645 (2015)] argued that the concept of the weak value of an observable of a pre- and post-selected quantum system cannot be applied when the expectation value of the observable in the initial state vanishes. Svensson's argument is analyzed and shown to be inconsistent using several examples.

A Model for the Transport of Sea-Spray Aerosols in the Coastal Zone

We study the dynamics of sea-spray particles in the coastal region of La Reunion Island on the basis of numerical simulations using the transport aerosol model MACMod (Marine Aerosol Concentration Model) and a survey of the aerosol size distributions measured at four locations at two different heights in the north-west part of the island. This allows evaluation of the performance of our model in case of pure marine air masses with implementation of accurate boundary conditions. First of all, an estimate of the aerosol concentration at 10-m height at the upwind boundary of the calculation domain is obtained using a revisited version of the MEDEX (Mediterranean Extinction) model. Estimates of the vertical profile of aerosol concentrations are then provided using aerosol data obtained at two different heights at the upwind boundary of the calculation domain. A parametrization of the vertical profiles of aerosol concentrations for maritime environment is proposed. The results are then compared to the vertical profiles of 0.532 $$\upmu $$ m aerosol particle extinction coefficient obtained from lidar data provided by the Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP) and also to the data provided by the Aerosol Robotic Network (AERONET). This allows validation of the complete vertical profiles in the mixed layer and shows the validity of satellite data for determination of the vertical profiles. Two kinds of simulation were made: one without a particle advection flux at the upwind boundary of the numerical domain, whereas the second simulation was made with a particle advection flux. In the first case, the influence of the distance to the shoreline on the local sea-spray dynamics is investigated. In the second set of simulation, the particles issued from the local production in the surf zone near the shoreline are mixed with aerosols advected from the remote ocean. A good agreement between the model calculations using our boundary conditions and the data was found. The present results then attest the ability of this kind of model, as a first approach to predicting the local transport of sea-spray particles in a pure marine environment.

Influence of atmospheric parameters on vertical profiles and horizontal transport of aerosols generated in the surf zone

The vertical and horizontal transport of aerosols generated over the surf zone is discussed. Experimental data were collected during the second campaign of the Surf Zone Aerosol Experiment that took place in Duck NC (USA) in November 2007. The Empirical Orthogonal Function (EOF) method was used to analyze the vertical concentration gradients, and allowed separating the surf aerosols from aerosols advected from elsewhere. The numerical Marine Aerosol Concentration Model (MACMod) supported the analysis by confirming that the concentration gradients are more pronounced under stable conditions and that aerosol plumes are then more confined to the surface. The model also confirmed the experimental observations made during two boat runs along the offshore wind vector that surf-generated aerosols are efficiently advected out to sea over several tens of kilometers.

Geological controls on palaeo-environmental change in a tectonic rain shadow, southern New Zealand

This study is a multidisciplinary synthesis that quantifies the geological processes that control surface palaeo-environmental change, and the associated biota, in an evolving Pliocene–Quaternary orographic rain shadow, South Island of New Zealand. The processes are relevant to evolution of older and more complex rain shadows of the Andes, western North America, and the Himalaya. Local rain shadow aridification can be distinguished from global climate change using asymmetry of stable isotope signatures across a steep orographic mountain rainfall gradient, with δ18O and δD values as low as −13‰ and −95‰, respectively. Salination in the rain shadow results from evaporative concentration of marine aerosols on impermeable rocks, with only minor water–rock interaction, and a distinct flora has developed on these sites. Natural coal fires, burning in excess of 1000°C, contributed to maintenance of savannah environments. Uplift of fold mountains, especially in the Quaternary, has maintained salination sites and their flora as well as lignites for coal fires, with these environments progressively migrating laterally at 1–10m/thousand years. Numerous river capture events accompanied Quaternary mountain uplift in the driest part of the rain shadow because of low erosion rates, and these have facilitated radiation of freshwater galaxiid fish into nine sister species, whereas an adjacent region with less complex tectonics and topography has only one species from that lineage. The combination of tectonic uplift and rain shadow aridification has two main effects on the surface environment: (a) topographic evolution and biological evolution are occurring at similar rates, and growth of mountains has facilitated fish speciation; (b) mountain uplift causes local environmental rejuvenation, so that salination and local coal fires, and the biological effects of these phenomena, are maintained over long time scales by lateral migration.

Wintertime Arctic Ocean sea water properties and primary marine aerosol concentrations

Abstract. Sea spray aerosols are an important part of the climate system through their direct and indirect effects. Due to the diminishing sea ice, the Arctic Ocean is one of the most rapidly changing sea spray aerosol source areas. However, the influence of these changes on primary particle production is not known. In laboratory experiments we examined the influence of Arctic Ocean water temperature, salinity, and oxygen saturation on primary particle concentration characteristics. Sea water temperature was identified as the most important of these parameters. A strong decrease in sea spray aerosol production with increasing water temperature was observed for water temperatures between −1°C and 9°C. Aerosol number concentrations decreased from at least 1400 cm−3 to 350 cm−3. In general, the aerosol number size distribution exhibited a robust shape with one mode close to dry diameter Dp 0.2 μm with approximately 45% of particles at smaller sizes. Changes in sea water temperature did not result in pronounced change of the shape of the aerosol size distribution, only in the magnitude of the concentrations. Our experiments indicate that changes in aerosol emissions are most likely linked to changes of the physical properties of sea water at low temperatures. The observed strong dependence of sea spray aerosol concentrations on sea water temperature, with a large fraction of the emitted particles in the typical cloud condensation nuclei size range, provide strong arguments for a more careful consideration of this effect in climate models.

Development of a 2D marine aerosol transport model: Application to the influence of thermal stability in the marine atmospheric boundary layer

The present paper deals with the implementation of the Marine Aerosol Concentration Model (MACMod) in a Mediterranean coastal area. MACMod is a 2D unsteady model dedicated to the atmospheric transport of marine aerosols in the Marine Atmospheric Boundary Layer (MABL). The model predictions were compared to aerosol size distributions measured during experimental campaigns conducted in the French coastal Mediterranean area, for various experimental conditions. The results show a good agreement between the model calculations and the experimental data. In addition, the influence of the main parameters governing the transport of sea-salts in the MABL in case of offshore winds is investigated using model calculations. In particular, our work allows quantification of decrease or increase in concentrations dependent on the thermal stability conditions (compared to neutral case). It is also found that the thermal stability has an increased effect for low wind speeds. The concentration at 10 m height of submicron and supermicron aerosols show an opposite behavior with regard to the stability conditions, i.e., concentration of the former is increased for stable conditions, whereas it is decreased for the latter. When the wind speed exceeds 15 ms − 1 , the thermal stability effect is lowered.

Characterization of Florida red tide aerosol and the temporal profile of aerosol concentration

Red tide aerosols containing aerosolized brevetoxins are produced during the red tide bloom and transported by wind to coastal areas of Florida. This study reports the characterization of Florida red tide aerosols in human volunteer studies, in which an asthma cohort spent 1 h on Siesta Beach (Sarasota, Florida) during aerosolized red tide events and non-exposure periods. Aerosol concentrations, brevetoxin levels, and particle size distribution were measured. Hourly filter samples were taken and analyzed for brevetoxin and NaCl concentrations. In addition, the aerosol mass concentration was monitored in real time. The results indicated that during a non-exposure period in October 2004, no brevetoxin was detected in the water, resulting in non-detectable levels of brevetoxin in the aerosol. In March 2005, the time-averaged concentrations of brevetoxins in water samples were moderate, in the range of 5–10 μg/L, and the corresponding brevetoxin level of Florida red tide aerosol ranged between 21 and 39 ng/m 3. The temporal profiles of red tide aerosol concentration in terms of mass, NaCl, and brevetoxin were in good agreement, indicating that NaCl and brevetoxins are components of the red tide aerosol. By continuously monitoring the marine aerosol and wind direction at Siesta Beach, we observed that the marine aerosol concentration varied as the wind direction changed. The temporal profile of the Florida red tide aerosol during a sampling period could be explained generally with the variation of wind direction.

On the aerosol number concentration–wind speed relationship during a severe cyclonic storm over south Indian Ocean

Measurements of the number concentration and size distribution of aerosols in the range of 0.5–20 μm diameter were made during a severe cyclonic storm in the Southern Hemisphere at 53.3°S, 52.5°E on 19 February 2004. Data were analyzed to study the aerosol number concentration–wind speed relationship. It was found that in conformity with past observations, total aerosol number concentration increases with increase in wind speed from 4 to 11 m s−1, measured at 10 m above sea level. However, contrary to most of the earlier studies, total aerosol number concentration decreases with increase in the wind speed from 16 to 22 m s−1 and then maintains an almost constant value up to the maximum wind speed of 33.1 m s−1. The total aerosol number concentration varies a little with wind speed in the range of 11–16 m s−1. While increase in the total aerosol number concentration corresponding to the increase in wind speed from 4 to 11 m s−1 is spread over the whole range of particle sizes, decrease in the aerosol number concentration associated with increase in wind speed from 16 to 22 m s−1 is mainly due to decrease in the concentration of particles of &lt;1 μm. The increase in aerosol number concentration is well recognized as being due to the enhanced bubble‐breaking activity at the sea surface and increased entrainment of sea‐salt particles, once produced. We propose that decrease in the aerosol number concentration may possibly occur because of the scavenging of aerosols by larger seawater drops injected into the atmosphere at high wind speeds. This scavenging process may act as a built‐in sink, which becomes operative at high wind speeds and restricts the enhancement in concentration of marine aerosols.

An ultrafine sea‐salt flux from breaking waves: Implications for cloud condensation nuclei in the remote marine atmosphere

Sea‐salt aerosol (SSA) is an important constituent of natural marine aerosol to which anthropogenic aerosols must be compared when assessing their climatic influence. Size distributions of particles, produced by bubbles from coastal oceanic breaking waves, were found to have sizes as small as 0.01 μm, with 60% smaller than 0.1 μm diameter. The thermal stability of these particles and their growth factor measured under increasing humidity indicate that most are sea salt. These SSA size distributions were used in conjunction with the measured number flux for bubbles from coastal breaking waves to develop a new sea‐salt source function. This source function and the associated SSA flux compare favorably with previously published estimates available for sizes larger than 0.5 μm but extend the source function down to much smaller sizes. When this SSA flux is applied to oceanic whitecaps that have a highly nonlinear dependence on wind speed, it implies strong regional and temporal differences in the open ocean surface number flux. In marine regions with little continental impact we estimate that this SSA flux can contribute ∼5–90% of the marine cloud condensation nuclei (CCN), with the rest accounted for by the flux of aerosol entrained from the free troposphere. These two fluxes are large enough to account for commonly observed aerosol and CCN concentrations in the clean MBL without requiring a nucleation source in the MBL. These observations have significant implications for modeling marine aerosol concentrations and evolution.

Holistic model for atmospheric corrosion Part 4 – Geographic information system for predicting airborne salinity

This paper is the fourth in a series of five papers addressing the factors controlling and predicting marine aerosol concentrations on land. It outlines the procedures used to develop a geographic information system (GIS) model of airborne salinity across Australia. The basic mathematical formulae have been presented previously, and this paper outlines how these formulae are applied in a GIS system. While the basic formulae are based on models of the processes controlling the formation and distribution of marine aerosols, some constants have been determined empirically. These constants are established by regression analysis using data derived and presented previously from a long range study of atmospheric salinity levels in a transect across the Australian State of South Australia. The model was then tested with databases of airborne salinity measurements throughout Australia and was shown to possess a high level of accuracy. It was then used to predict the salinity across Australia, with a salinity map of Australia being produced. A number of features of the map are discussed. Lastly, the model is used to illustrate the role of coastal forms in controlling salinity in adjacent regions.

Holistic model for atmospheric corrosion: Part 2 - Experimental measurement of deposition of marine salts in a number of long range studies

This paper is the second in a series looking at understanding the factors controlling and predicting marine aerosol concentration on land. It looks at results from three transects across the Australian continent. In each transect, the airborne salinity was measured, using the wet candle method at distances from 10 m to 40-300 km from the coast. The positions of the transects were selected to give a significant variation in the factors controlling salt production and transport. For example, one transect in South Australia was established where both high whitecap activity is likely to promote salt production and flat terrain and prevailing winds are likely to favour transport. Another, in Queensland, was established where calm seas will limit salt production and very seasonal winds and high relative humidity and rainfall will limit transport. On the basis of this experimental study, the general validity of the fundamental concepts put forward in Part 1 is assessed. Further, the feasibility of building a mathematical model to predict salinity is determined and the main factors causing variations in salinity on land are outlined. The results are then used to assist in the interpretation of previous work in the literature.

Is aerosol production within the remote marine boundary layer sufficient to maintain observed concentrations?

To evaluate the impact of aerosols on climate we must consider the aerosol dynamics of the remote marine atmosphere. Marine aerosols are subject to losses due to precipitation, dry deposition, and coagulation; yet, observed remote marine aerosol concentrations and size distributions are relatively constant. This maintenance of the aerosol distribution requires a particle source. This work focuses on the potential of H2SO4 nucleation within the marine boundary layer (MBL) to supply these particles. Spatial and temporal variability in meteorology and species concentrations are considered in a mathematical model to evaluate the effect of natural deviations from average MBL conditions on the highly nonlinear aerosol system. A dynamic, vertically dimensioned, size‐resolved aerosol model is used with parameterized heterogeneous chemical processes. The results suggest that MBL nucleation may be an important source of new particle number in the remote MBL. However, though our model shows that typical remote MBL aerosol distributions can on average be maintained by MBL nucleation and sea‐salt emissions, large oscillations in particle number concentration occur. Because such oscillations are only occasionally reported in measurements, MBL nucleation may not be the dominant source of new particles in the remote MBL. The nucleation events, which cause these oscillations, are predicted to occur at the top of the MBL after rain and/or entrainment of clean free tropospheric air. Predictions are particularly sensitive to the H2SO4 accommodation coefficient, nucleation tuner, and washout efficiency. Reduction of the accommodation coefficient is shown to increase the predicted accumulation mode concentration because the nucleation rate is enhanced. Entrainment of clean free tropospheric air is shown to increase the frequency of nucleation events within the MBL and may help to explain the observed correlation between subsidence and MBL small particles. A small constant addition of particles from the free troposphere, ocean, etc. suppresses H2SO4 nucleation and can lead to a reduction in total predicted aerosol number. This is because nucleation events require low total aerosol surface area and the constant addition of particles reduces the severity of aerosol surface area minimums. Larger external aerosol sources can maintain the observed remote MBL aerosol distribution. However, the temporal and spatial variability of such sources could have a large impact on aerosol concentrations and requires further investigation.

Verification of different techniques for the measurement of marine aerosols in coastal areas

processes as well as in the production and dynamics of marine aerosols. Marine aerosol concentrations are significantly higher in such areas. Aerosols, in the zone of direct interaction between the air and the ocean surface are characterized by rapid time-space changes of concentrations. The continual changes in aerosol concentrations are due both to external changes, such as variations in particle input, and internal changes like coalescence, coagulation and evaporation. These processes result in the variations of aerosol sizes, which also influences particle removal from the marine boundary layer. This means that changes in aerosol concentration in the marine boundary layer are connected to with the changes in the spectrum of marine aerosol size distribution functions. This spectrum is complex and depends strongly on weather conditions in the marine boundary layer. In order to determine aerosol size distribution and concentration six cascade impactors, a particle measurement system and a lidar were employed. The impactor is an inertial separator of particles whose separation effectiveness depends on the nozzle diameter and the Reynolds number. It was confirmed that the effectiveness of catching particles from the size range r E [ 1, 10 pm] and larger is loaded with an error of not greater than 24.5 %. A particle measurement system CSASP-100~HV(Sp) is a water droplet spectrometer which operates on the principle that the light scattered by a particle within a high intensity laser beam is directly a function of its size. Particles produce pulses of radiant energy during transit through the laser beam. These light pulses are sensed by detectors and are read by two peak readers. System CSASP- 1 00-HV provides means of resolving and sizing particles in an in-situ mode. The CSASP- 1 00-HV is capable of sizing particles into fifteen size classes (size ranges: 247 urn; 2-32 pm; 1-16 pm; 0.5-8 pm). In the lidar method, laser pulses are transmitted into the atmosphere and backscattered radiation is collected by an optical telescope and detected. Mie scattering from particles and Raleigh scattering from molecules provide strong signals observed in backscattering in lidar sounding of the free atmosphere. These scattering processes are elastic, i.e.. the scattered photons have the same frequency as the incoming light. Lidar method allows for remote measurements of vast areas which range is closely related to the platform arrangement for the

Marine aerosol concentrations at different locations of the northern hemisphere

Marine aerosol concentrations at different locations of the northern hemisphere