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Cyclones are expected to increase the vertical transport of sea salt aerosols (SSAs), which may significantly impact the climate by increasing the cloud condensation nuclei (CCN)/cloud droplets (Nd) population, hence changing the radiation reflected back to space. In this study, high temporal resolution (1 h) aerosol composition measurements were performed during a survey in the southern hemisphere middle and high latitudes during the period 23 February 2018 to 4 March 2018. The characteristics of sea salt aerosols (SSA) during three cyclones were observed during the survey. The level of SSA increased very little with increasing wind speed during the cyclones, which is quite different from the expected case that wind speed will increase SSA concentration. However, the size of sea salt aerosol particles during the cyclones were larger than during the no-cyclone periods. It seems that the generation of sea salt aerosols is enhanced during cyclones, but the SSA concentration near the sea surface does not increase. Calculations suggest that more than 23 % of SSAs can be transported upward during a cyclone period which can result in considerable quantities of SSAs being transported to high altitudes. The upward transport also lowers the level of SSAs in the lower atmosphere. Additionally, the transport of SSAs to the high atmosphere during cyclones increases the CCN burden in the marine boundary layer. This study extends the knowledge of SSA generation and transport during cyclones, which has implications to climate change. [ABSTRACT FROM AUTHOR]

Airborne NASA Langley Research Center (LaRC) High Spectral Resolution Lidar-2 (HSRL-2) measurements acquired during the recent NASA Earth Venture Suborbital-3 (EVS-3) Aerosol Cloud Meteorology Interactions over the Western Atlantic Experiment (ACTIVATE) revealed elevated particulate linear depolarization associated with aerosols within the marine boundary layer. These observations were acquired off the east coast of the United States during both winter and summer 2020 and 2021 when the HSRL-2 was deployed on the NASA LaRC King Air aircraft. During 20 of 63 total flight days, particularly on days with cold air outbreaks, linear particulate depolarization at 532 nm exceeded 0.15–0.20 within the lowest several hundred meters of the atmosphere, indicating that these particles were non-spherical. Higher values of linear depolarization typically were measured at 355 nm and lower values were measured at 1,064 nm. Several lines of evidence suggest that these non-spherical particles were sea salt including aerosol extinction/backscatter ratio (“lidar ratio”) values of 20–25 sr measured at both 355 and 532 nm by the HSRL-2, higher values of particulate depolarization measured at low (< 60%) relative humidity, coincident airborne in situ size and composition measurements, and aerosol transport simulations. The elevated aerosol depolarization values were not correlated with wind speed but were correlated with salt mass fraction and effective radius of the aerosol when the relative humidity was below 60%. HSRL-2 measured median particulate extinction values of about 20 Mm−1 at 532 nm associated with these non-spherical sea salt particles and found that the aerosol optical depth (AOD) contributed by these particles remained small (0.03–0.04) but represented on average about 30%–40% of the total column AOD. Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) spaceborne lidar aerosol measurements during several cold air outbreaks and CALIOP retrievals of column aerosol lidar ratio using column AOD constraints suggest that CALIOP operational aerosol algorithms can misclassify these aerosols as dusty marine rather than marine aerosols. Such misclassification leads to ∼40–50% overestimates in the assumed lidar ratio and in subsequent retrievals of aerosol optical depth and aerosol extinction.

Natural aerosols and their interactions with clouds remain an important uncertainty within climate models, especially at the poles. Here, we study the behavior of sea salt aerosols (SSaer) in the Arctic and Antarctic within 12 climate models from CMIP6. We investigate the driving factors that control SSaer abundances and show large differences based on the choice of the source function, and the representation of aerosol processes in the atmosphere. Close to the poles, the CMIP6 models do not match observed seasonal cycles of surface concentrations, likely due to the absence of wintertime SSaer sources such as blowing snow. Further away from the poles, simulated concentrations have the correct seasonality, but have a positive mean bias of up to one order of magnitude. SSaer optical depth is derived from the MODIS data and compared to modeled values, revealing good agreement, except for winter months. Better agreement for aerosol optical depth than surface concentration may indicate a need for improving the vertical distribution, the size distribution and/or hygroscopicity of modeled polar SSaer. Source functions used in CMIP6 emit very different numbers of small SSaer, potentially exacerbating cloud‐aerosol interaction uncertainties in these remote regions. For future climate scenarios SSP126 and SSP585, we show that SSaer concentrations increase at both poles at the end of the 21st century, with more than two times mid‐20th century values in the Arctic. The pre‐industrial climate CMIP6 experiments suggest there is a large uncertainty in the polar radiative budget due to SSaer. Plain Language Summary: Aerosols emitted from the ocean, such as sea salt particles (aerosols), are critical for the climate of polar regions. However, there is still uncertainty in their representation in climate models. The purpose of this work is to evaluate the representation of sea salt aerosols (SSaer) in the Arctic and Antarctic in a recent model inter‐comparison initiative, and to assess the consequences for our understanding of present‐day and future polar climate. We find that the models disagree between them and with observations from ground stations and from space. This suggests that the formulation of sea salt emissions in global models is not adapted for polar regions. With sea ice retreat, SSaer will most likely increase in the future, which makes addressing the current uncertainty an important next step for the scientific community. Key Points: CMIP6 models have a large uncertainty in present day sea salt aerosol abundance at the polesModel performance is degraded closer to the poles suggesting inadequate emission sources within the polar regionsBoth present and future radiative balance at the poles is uncertain because of sea salt aerosols [ABSTRACT FROM AUTHOR]

We evaluate the effects of rapidly changing Arctic sea ice conditions on sea salt aerosols (SSA) produced by oceanic wave‐breaking and the sublimation of wind‐lofted salty blowing snow on sea ice. We use the GEOS‐Chem chemical transport model to assess the influence of changing extent of the open ocean, multi‐year sea ice (MYI), first‐year sea ice (FYI), and snow depths on SSA emissions for 1980–2017. We combine snow depths from the Lagrangian snow‐evolution model (SnowModel‐LG) together with an empirically‐derived snow salinity function of snow depth to derive spatially and temporally varying snow surface salinity over Arctic FYI. We find that pan‐Arctic SSA surface mass concentrations have increased by 6%–12% decade−1 during the cold season (November–April) and by 7%–11% decade−1 during the warm season (May–October). The cold season trend is due to increasing blowing snow SSA originating from FYI: as MYI is replaced by FYI with thinning snow depths, snow surface salinity increases by more than 11% decade−1. During the warm season, rapid sea ice loss and thus increasing open ocean SSA are the cause of modeled SSA trends. Observations of SSA mass concentrations at Alert, Canada display positive trends during the cold season (10%–12% decade−1), consistent with our pan‐Arctic simulations. During fall, Alert observations show a negative trend (−18% decade−1), due to locally decreasing wind speeds and thus lower open ocean emissions. These significant changes in SSA concentrations could potentially affect past and future bromine explosions and Arctic climate feedbacks. Plain Language Summary: Suspended sea salt particles affect the climate and chemistry of the atmosphere. The main source of these particles is ocean wave breaking. In polar regions an additional source is the wind lofting of salty snow that is present on top of sea ice. Here we use model simulations to examine how changing Arctic conditions have impacted sea salt particles in the atmosphere. Our simulations show that the concentrations of sea salt particles have increased by more than 6% per decade over the 1980–2017 period. During cold months, this increase is due to saltier blowing snow particles as older sea ice with less salty snow is being replaced by younger sea ice with more salty snow. During warmer months, this increase is the result of larger open ocean emissions as sea ice is melting. These changes in sea salt particles could potentially affect Arctic bromine activation and climate. Key Points: Model predicts pan‐Arctic increase in sea salt aerosol (SSA) concentrations by 6%–12% decade−1 for 1980–2017Younger Arctic sea ice with thinner and saltier snow cause increasing blowing snow SSA emissions in winter‐springDuring summer‐fall, rapidly diminishing sea ice extent results in increasing open ocean SSA emissions [ABSTRACT FROM AUTHOR]

The Southern Ocean is often identified as a pristine aerosol environment, being distant from anthropogenic sources. We investigate anomalies in aerosol loading over the Southern Ocean due to stratospheric ozone depletion in historical simulations performed for the sixth Coupled Model Intercomparison Project. We explore direct influences of ozone depletion on aerosols via enhanced ultraviolet‐induced production of oceanic dimethyl sulfide (DMS), and indirect influences via changes in the Southern Hemisphere westerly jet, which impacts wind‐driven aerosol fluxes. We identify wind as the key driver of change for austral summertime aerosol, leading to increases in aerosol optical depth of up to 24% compared with the pre–ozone hole era. In contrast to previous studies, direct impacts on aerosol from ozone depletion and enhanced ultraviolet fluxes are less obvious. Our results show that the Southern Ocean summertime aerosol environment cannot be considered to be representative of pre–ozone hole conditions because stratospheric ozone depletion has indirectly increased marine aerosol fluxes. Plain Language Summary: Studies performed in the 2000s suggested that the Antarctic ozone hole would lead to increased marine biogeochemical activity, increasing the concentration of phytoplankton‐produced dimethyl sulfide, and therefore sulfate aerosol. Our analysis shows that this feedback is not significant in a range of state‐of‐the‐art Earth System Models. However, because the ozone hole influences the summertime near‐surface westerly jet, the impact of wind‐driven aerosol formation has increased by up to 24% over the Southern Ocean since stratospheric ozone depletion began. The Southern Ocean is typically considered a pristine environment for aerosols, especially during summer months. Our results imply that, far from being pristine, the Southern Ocean has experienced significant human‐induced change ever since Antarctic ozone depletion began. Key Points: Wind‐driven Southern Ocean aerosol fluxes are influenced by the ozone hole during austral summerAustral summer sea spray aerosol increased by 9.7% and dimethyl sulfide increased by 3% around 60°S between 1940 and 2014Indirect influences of ozone losses mean Southern Ocean aerosols cannot be considered to be representative of pristine conditions [ABSTRACT FROM AUTHOR]

The ground-based measurement of sea salt (SS) aerosol over the ocean requires the massive utilization of satellite-derived aerosol products. In this study, n-order spectral derivatives of aerosol optical depth (AOD) based on wavelength were examined to characterize SS and other aerosol types in terms of their spectral dependence related to their optical properties such as particle size distributions and complex refractive indices. Based on theoretical simulations from the second simulation of a satellite signal in the solar spectrum (6S) model, AOD spectral derivatives of SS were characterized along with other major types including mineral dust (DS), biomass burning (BB), and anthropogenic pollutants (APs). The approach (normalized derivative aerosol index, NDAI) of partitioning aerosol types with intrinsic values of particle size distribution and complex refractive index from normalized first- and second-order derivatives was applied to the datasets from a moderate resolution imaging spectroradiometer (MODIS) as well as by the ground-based aerosol robotic network (AERONET). The results after implementation from multiple sources of data indicated that the proposed approach could be highly effective for identifying and segregating abundant SS from DS, BB, and AP, across an ocean. Consequently, each aerosol's shortwave radiative forcing and its efficiency could be further estimated in order to predict its impact on the climate. [ABSTRACT FROM AUTHOR]

This study examines multiyear climate variability associated with sea salt aerosols and their contribution to the variability of shortwave cloud forcing (SWCF) using a 150 year simulation for preindustrial conditions of the Community Earth System Model version 1.0. The results suggest that changes in sea salt and related cloud and radiative properties on interannual timescales are dominated by the El Niño-Southern Oscillation cycle. Sea salt variability on longer (interdecadal) timescales is associated with low-frequency variability in the Pacific Ocean similar to the Interdecadal Pacific Oscillation but does not show a statistically significant spectral peak. A multivariate regression suggests that sea salt aerosol variability may contribute to SWCF variability in the tropical Pacific, explaining up to 20-30% of the variance in that region. Elsewhere, there is only a small sea salt aerosol influence on SWCF through modifying cloud droplet number and liquid water path that contributes to the change of cloud effective radius and cloud optical depth (and hence cloud albedo), producing a multiyear aerosol-cloud-wind interaction.

The direct and indirect radiative effects of sea salt aerosols (SSA) over the western Pacific Ocean of East Asia for the year 2014 are investigated by using an online-coupled regional chemistry-climate model (RIEMS-Chem) with a developed sea salt emission scheme (G03SSTRH) by considering the effects of sea surface temperature (SST) and relative humidity (RH) on sea salt generation. Model comparison with observations at coastal and island sites demonstrates the G03SSTRH scheme apparently improve model simulation for sea salt concentration, with the overall model-observation bias for PM 10 concentration reduced from 29% to 16% and more evident improvement at northern sites of the western Pacific. It is noteworthy that compared to the experiment with the old SSA emission scheme (G03), the G03SSTRH experiment substantially alters the spatial distribution of mass concentration and radiative effects of sea salt, shifting the maximum value center from the ocean northeast of Japan to the southern parts of the western Pacific with the maximum value increasing to some extent. SSA exerts a negative radiative effect at the top of atmosphere (TOA), in which direct radiative effect (DRE SSA) dominates over indirect radiative effect (IRE SSA) in the western Pacific. The oceanic and annual mean DRE SSA , IRE SSA , and total radiative effect (TRE SSA) are estimated to be −1.22 W/m2, −0.46 W/m2, and −1.65 W/m2, respectively, from the G03SSTRH experiment, which are 16%, 5%, and 12% stronger than those from the G03 experiment, and the seasonal mean DRE SSA in G03SSTRH are approximately 45% and 32% higher than those in G03 in summer and autumn. Distinct seasonality of SSA radiative effects is revealed in the G03SSTRH experiment, showing stronger DRE SSA and IRE SSA in summer and autumn than those in spring and winter, in marked contrast to the little seasonality in the G03 experiment. This study provides a comprehensive regional estimation of radiative effects induced by SSA and reveals the significant effect of different SSA emission schemes on both mass concentration, radiative effects and seasonal variation of SSA over the western Pacific. [Display omitted] • Sea salt emission scheme is developed by considering the effects of SST and RH. • New scheme improves sea salt prediction with NMB decreasing from 29% to 16%. • DRE SSA is higher in summer/autumn and IRE SSA peaks in autumn over the western Pacific Ocean. • Annual and oceanic mean DRE SSA and IRE SSA at TOA are estimated to be −1.2 and −0.5 Wm−2. [ABSTRACT FROM AUTHOR]

The ground-based measurement of sea salt (SS) aerosol over the ocean requires the massive utilization of satellite-derived aerosol products. In this study, n-order spectral derivatives of aerosol optical depth (AOD) based on wavelength were examined to characterize SS and other aerosol types in terms of their spectral dependence related to their optical properties such as particle size distributions and complex refractive indices. Based on theoretical simulations from the second simulation of a satellite signal in the solar spectrum (6S) model, AOD spectral derivatives of SS were characterized along with other major types including mineral dust (DS), biomass burning (BB), and anthropogenic pollutants (APs). The approach (normalized derivative aerosol index, NDAI) of partitioning aerosol types with intrinsic values of particle size distribution and complex refractive index from normalized first- and second-order derivatives was applied to the datasets from a moderate resolution imaging spectroradiometer (MODIS) as well as by the ground-based aerosol robotic network (AERONET). The results after implementation from multiple sources of data indicated that the proposed approach could be highly effective for identifying and segregating abundant SS from DS, BB, and AP, across an ocean. Consequently, each aerosol’s shortwave radiative forcing and its efficiency could be further estimated in order to predict its impact on the climate.

Frost flowers are clusters of highly saline ice crystals growing on newly formed sea ice or frozen lakes. Based on observations of particles derived from frost flowers in the Arctic, we formulate an observation-based parameterization of salt aerosol source function from frost flowers. The particle flux from frost flowers in winter has the order of 106 m-2 s-1 at the wind speed of 10 m s-1, but the source flux is highly localized to new sea ice regions and strongly dependent on wind speed. We have implemented this parameterization into the regional Weather Research and Forecasting model with Chemistry initialized for two wintertime scenarios. The addition of sea salt aerosol emissions from frost flowers increases averaged sea salt aerosol mass and number concentration and subsequent cloud droplet number. This change of cloud droplet number concentration increases downward longwave cloud radiative forcing through enhanced cloud optical depth and emissivity. The magnitude of this forcing of sea salt aerosols from frost flowers on clouds and radiation, however, contributes negligibly to surface warming in Barrow, Alaska, in the wintertime scenarios studied here. Key Points We evaluate a parameterization of salt aerosol from frost flowers in WRF-Chem The modeled salt explains half of the observed submicron salt aerosol Longwave cloud forcing increases but does not add to Arctic surface warming ©2013. American Geophysical Union. All Rights Reserved.

The MONterey Aerosol Research Campaign (MONARC) in May–June 2019 featured 14 repeated identical flights off the California coast over the open ocean at the same time each flight day. The objective of this study is to use MONARC data along with machine learning analysis to evaluate relationships between both supermicrometer sea salt aerosol number (N>1) and volume (V>1) concentrations and wind speed, wind direction, sea surface temperature (SST), ambient temperature (Tamb), turbulent kinetic energy (TKE), relative humidity (RH), marine boundary layer (MBL) depth, and drizzle rate. Selected findings from this study include the following: (i) Near surface (<60 m) N>1 and V>1 concentration ranges were 0.1–4.6 cm−3 and 0.3–28.2 μm3 cm−3, respectively; (ii) four meteorological regimes were identified during MONARC with each resulting in different N>1 and V>1 concentrations and also varying horizontal and vertical profiles; (iii) the relative predictive strength of the MBL properties varies depending on predicting N>1 or V>1, with MBL depth being more highly ranked for predicting N>1 and with TKE being higher for predicting V>1; (iv) MBL depths >400 m (<200 m) often correspond to lower (higher) N>1 and V>1 concentrations; (v) enhanced drizzle rates coincide with reduced N>1 and V>1 concentrations; (vi) N>1 and V>1 concentrations exhibit an overall negative relationship with SST and RH and an overall positive relationship with Tamb; and (vii) wind speed and direction were relatively weak predictors of N>1 and V>1. Key Points: Vertical and horizontal profiles of supermicron sea salt aerosol concentrations are related to synoptic conditions and air mass historyMarine boundary layer depth (turbulent kinetic energy) is the best predictor for supermicron sea salt aerosol number (volume) concentrationDrizzle rate is the second most influential parameter for both supermicron sea salt aerosol number and volume concentration [ABSTRACT FROM AUTHOR]

Identifying which factors among the planetary boundary layer (PBL) scheme, grid resolution, and source or sink terms dominantly influence the sea salt aerosol (SSA) spatial distribution is necessary. The dependence of SSA transport on PBL processes was investigated using a numerical weather prediction (NWP) model with a grid scale of ∼143 m. Size-segregated SSA transport during Typhoon Hagibis, which made landfall in Japan in 2019, was simulated using the Weather Research and Forecasting (WRF) model. The PBL schemes of Yonsei University (YSU), scale-aware YSU (Shin and Hong, 2015's scheme, SH) and Mellor-Yamada Nakanishi-Niino (MYNN), and large-eddy simulation (LES) subjected to turbulence transition enhancement via a cell perturbation method were tested to evaluate the reproducibility of observed values of wind speed, surface pressure, relative humidity, and temperature at meteorology masts. The results showed that wind speed was most influenced by the selection of the PBL scheme and LES. The distance from the coastline, as determined by the wind direction during the most intense typhoon stage, was correlated with a decrease in the time averaged SSA concentration when the storm moved inland. Despite the simulated SSA emission scheme's high sensitivity to wind speed (nearly 3rd power), the near-surface average concentration was less sensitive to the PBL schemes and LES selection than wind speed. However, the maximum arrival of the SSA differed by ∼20 % during the most vigorous stage of the typhoon. Budget analysis of the SSA transport equation highlighted that the advection term and gravity settling were most dependent on the PBL schemes and LES. The impacts of both factors on SSA transport were not limited to near-surface tendencies but were in a broader range over the atmosphere, up to 1–2 km. These results indicated that the vertical structure of the SSA field over the boundary layer depended on the PBL schemes and LES, thereby modulating the inland arrival of the SSA. [ABSTRACT FROM AUTHOR]

Abstract: The sea ice surface is thought to be a major source of sea salt aerosol, suggesting that sodium records of polar ice cores may trace past sea ice extent. Here we test this possibility for the Arctic, using a chemical transport model to simulate aerosol emission, transport, and deposition in the satellite era. Our simulations suggest that sodium records from inland Greenland ice cores are strongly influenced by the impact of meteorology on aerosol transport and deposition. In contrast, sodium in coastal Arctic cores is predominantly sourced from the sea ice surface and the strength of these aerosol emissions controls the ice core sodium variability. Such ice cores may therefore record decadal to centennial scale Holocene sea ice changes. However, any relationship between ice core sodium and sea ice change may depend on how sea ice seasonality impacts sea salt emissions. Field‐based observations are urgently required to constrain this. [ABSTRACT FROM AUTHOR]

Salinization of surface and groundwater has been directly linked to the area of road surfaces in a watershed and the subsequent wintertime maintenance used to keep roads free of snow and ice. Most studies that explore road salt in snow along roadways limit the study to within 100 m from a roadway and conclude that there is negligible deposition of de-icing salt at distances greater than 100 m. In this study, we analyze the ion content of the southern New Hampshire snowpack and use Mg2+ as a conservative sea-salt tracer to calculate sea salt and non-sea salt fractions of Cl-. There is a minimum of 60% non-sea salt Cl-, which we attribute to road salt, in the snowpack at our study sites 115 to 350 m from the nearest maintained roadways. This suggests that larger areas need to be considered when investigating the negative impact of Cl- loading due to winter-time maintenance. [ABSTRACT FROM AUTHOR]

This study investigates the potential of DUSTRAN, a dust dispersion modeling system developed by Pacific Northwest National Laboratory, to model the transport of sea salt aerosols (SSA). Results from DUSTRAN simulations run with historical meteorological data were compared against privately-measured chloride data at the near coastal Maine Yankee Nuclear Power Plant (NPP) and the Environmental Protection Agency-measured CASTNET data from Acadia National Park (NP). The comparisons have provided both encouragement as to the practical value of DUSTRAN's CALPUFF model and suggestions for further software development opportunities. All modeled concentrations were within one order of magnitude of those measured and a few test cases showed excellent agreement between modeled and measured concentrations. However, there is a lack of consistency which may be due to inaccurate extrapolation of meteorological data, underlying model physics, and the source term. Future research will refine the software to better capture physical phenomena. Overall, results indicate that with parameter refinement, DUSTRAN has the potential to simulate atmospheric chloride transport from known sources to inland sites for the purpose of determining the corrosion susceptibility of various structures, systems, and components (SSC) at near coastal sites, and for other relevant air quality studies. [ABSTRACT FROM AUTHOR]

Currently, we know little about the effects of anthropogenic aerosols (AAs) and sea salt aerosols (SSAs) on heavy precipitation over the densely populated coastal areas. In this view, we developed a local aerosol activation parametrization scheme which conforms to the Yangtze River Delta (YRD) characteristics using cloud condensation nucleus (CCN) with supersaturation at 0.4 (CCN 0.4) and aerosol optical depth (AOD) data at 550 nm (AOD 550) to improve the model performance. Meanwhile, we simulated a heavy precipitation over the YRD during early summer using the WRF-Chem model (version 4.1) with the Morrison microphysics scheme. Increased AAs and SSAs presented opposite responses in droplets concentrations and precipitation intensity. The increased AAs increased the aerosol concentrations, leading to more but smaller droplets; and the cloud droplets mixing ratio Q c was slightly increased by 17.7% due to the weakened auto-conversion from droplets to raindrops, while the rain mixing ratio Q r was decreased by about 5.7%. On the contrary, presence of SSAs increased the effective (EFC) radius of cloud droplets because of the larger particles. Along with increased AAs, due to the influences of decreased Q r and smaller droplets, probability density function (PDF) of the hourly surface rain rates shifted to the smaller values (< 0.5 mm/h), which was caused by lowered latent heat release resulting from the enhanced rain evaporative cooling and weakened condensation rate, weakening the convective intensity and updrafts. Meanwhile, decreased updrafts resulted in fewer cloud droplets being transformed to the upper air, less accretion of droplets by ice crystal and snow, and reduced ice mixing ratio Q i and snow mixing ratio Q s. The averaged surface precipitation accumulated for 24 h decreased by about 7.2%, and the intensity of radar reflectivity was decreased by about 7.0%. In contrast, presence of SSAs enhanced the auto-conversion droplets and weakened the evaporation of raindrops, thus increasing the Q r. In this case, the 24-h accumulated averaged surface rainfall was increased by about 30.1% with the larger radar reflectivity and increased area of large reflectivity values (> 20 dbz). The latent heat release and related microphysical processes were enhanced due to the changes of conversion rate, which, together with the increased Q r and larger droplets, strengthened the precipitation, increased the incidence of heavier precipitation (> 2 mm/h), and enhanced the ice-phase microphysical processes. • Different effects of anthropogenic and sea salt aerosols are revealed during a heavy precipitation event. • Aerosol activation process is optimized to improve the model performance by using satellite data. • Enhanced convection and following microphysical processes due to sea salt result in more occurrence of heavier rainfall. [ABSTRACT FROM AUTHOR]

Inland deposition of sea salt aerosol (SSA) particles emitted over the ocean is studied via numerical and theoretical models. The focus is on the large particles that contribute most to the total mass deposition. Large eddy simulations of idealized sea wind are used to investigate the development of the particle plume over land for different particle sizes and to validate some of the assumptions in the theoretical model. An existing theoretical modeling framework for particle dispersion in the atmospheric boundary layer is adapted to the problem of SSA deposition and it is shown to be adequate for the large particles of interest here. The decay of monodisperse SSA particle deposition flux with distance from the shoreline is shown to have a power-law behavior far from the shoreline. A complete model for predicting mass deposition as a function of distance is formulated and shown to present reasonable agreement with existing data. [ABSTRACT FROM AUTHOR]

Salinization of surface and groundwater has been directly linked to the area of road surfaces in a watershed and the subsequent wintertime maintenance used to keep roads free of snow and ice. Most studies that explore road salt in snow along roadways limit the study to within 100 m from a roadway and conclude that there is negligible deposition of de-icing salt at distances greater than 100 m. In this study, we analyze the ion content of the southern New Hampshire snowpack and use Mg2+ as a conservative sea-salt tracer to calculate sea salt and non-sea salt fractions of Cl−. There is a minimum of 60% non-sea salt Cl−, which we attribute to road salt, in the snowpack at our study sites 115 to 350 m from the nearest maintained roadways. This suggests that larger areas need to be considered when investigating the negative impact of Cl− loading due to winter-time maintenance.

ABSTRACT On the night of 2 January 2014, an aircraft on approach to Cork airport was required to abort a landing attempt due to sea salt aerosol ( SSA) accretion on the windscreen. The salt reduced forward-facing visibility to dangerously low levels and prohibited a safe approach by the aircraft. A landing was eventually effected on the 3rd attempt after a light rain shower cleared enough of the contaminant to allow the pilot to view the runway lights and markings. This was the first time such an incident was recorded by Ireland's Air Accident Investigation Unit. This paper elaborates the meteorological conditions present at the time the SSA became a visibility hazard. The atmospheric boundary layer was thermodynamically unstable and had a relatively dry airmass and the surface and upper level winds were high. SSA formation mechanisms are described in terms of the relationship between SSA concentration enhancement and meteorological variables. A brief comparison between the meteorological conditions surrounding this and another notable event documented by the US naval service is made. The potential for SSA to be a significant hazard to aviation and the recommendations for further research are considered. [ABSTRACT FROM AUTHOR]

A yearly survey in a piezometric network was realized in the Litorale Romano Natural Reserve (Rome, Central Italy), collecting water table and chemo-physical data. Monthly chemo-physical surveys highlighted a groundwater salinization variability in a coastal unconfined aquifer. The aquifer is mostly composed by aeolian sands of a still preserved dune ridge environment, on which a pine forest develops. The groundwater salinity variability resulted is connected to the wind pattern and rainfalls. In fact, wind speed higher than 4 m/s is responsible for generating sea salt aerosols (SSA) from sea surface. A statistical analysis was performed for wind with a speed higher than 4 m/s, to detect wind orientation. The dry deposition of SSA on the tree foliage appeared correlated to the westerly winds, blowing in the springtime. When the rainy season occurs, the SSA is washed out from the trees and it is directed to groundwater, where an enhancement of the Electrical Conductivity (EC) values is noticed. Whenever rain events occur and winds are not westerly, a dilution of groundwater salinity takes place and consequently a reduction of EC. Chemical analyzes were realized as well. They confirmed that groundwater of piezometers located close to the coast line is enriched of SSA elements. [ABSTRACT FROM AUTHOR]

A regional climate model, RIEMS-POM, was used to study the direct radiative forcing (DRF) of sea salt on precipitation, sea surface temperature (SST) and summer circulation over East Asia with aerosol dataset from GOCART. The simulations predicted negative DRFs of −0.87 W m −2 at the surface and −1.40 W m −2 at the top of the atmosphere by sea salt. Results from the simulations suggest the forcing of sea salt produces a slight positive temperature anomaly and a reduction in precipitation over Southern China, accompanied by an opposite trend north of 40°N in Northern and Northeastern China. The tendency of wetting in North and drying in South by sea salt was mainly determined by the wind field, the vertical motion, as well as the local evaporation anomalies. The impacts of sea salt on SST suggest that the net surface shortwave radiative flux and the changes in convective cloud are important in forming the decreased SST throughout the year, while the northward oceanic heat transport anomaly and the other heat flux anomalies contribute relatively smaller. The feature by sea salt on SST imposes an extra force from the atmosphere to the ocean. The sea salt could also diminish the land-sea temperature contrast (LSTC) in summer and therefore the climatological summer circulation over East Asia, leading to reduced precipitation in Southern China. All these climatic feedbacks, such as LSTC and precipitation anomaly, will be attenuated when the SST is fixed. [ABSTRACT FROM AUTHOR]

Using a coated-insert flow tube reactor coupled to a low-energy electron-impact mass spectrometer with molecular beam sampling, we studied uptake of NO by sea salt at room temperature and [NO] = 8⋅10 − 4⋅10 molecule cm. The radical uptake coefficient γ( t) is time dependent: its initial value ( γ) decreases exponentially with the characteristic time ( τ) to its steady-state value ( γ) at given [NO]. The parameters γ, γ and τ depend on [NO], whereas γ is water vapor independent at [HO] = 8⋅10 − 1.6⋅10 molecule cm and RH ≤ 0.5 %. HCl and NO are uptake products detected in the gas phase. We used these findings to estimate γ values under tropospheric conditions for urban coastal and remote marine environments: at high NO (~90 ppt), the time dependence becomes important, and the γ value averaged over the aerosol lifetime is 4⋅10; at low NO (~1 ppt), the radical uptake is time independent and proceeds faster with γ = 8⋅10 [ABSTRACT FROM AUTHOR]