The Atlantic Tradewind Ocean-Atmosphere Mesoscale Interaction Campaign (ATOMIC) took place from 7 January to 11 July 2020 in the tropical North Atlantic between the eastern edge of Barbados and 51∘ ...W, the longitude of the Northwest Tropical Atlantic Station (NTAS) mooring. Measurements were made to gather information on shallow atmospheric convection, the effects of aerosols and clouds on the ocean surface energy budget, and mesoscale oceanic processes. Multiple platforms were deployed during ATOMIC including the NOAA RV Ronald H. Brown (RHB) (7 January to 13 February) and WP-3D Orion (P-3) aircraft (17 January to 10 February), the University of Colorado's Robust Autonomous Aerial Vehicle-Endurant Nimble (RAAVEN) uncrewed aerial system (UAS) (24 January to 15 February), NOAA- and NASA-sponsored Saildrones (12 January to 11 July), and Surface Velocity Program Salinity (SVPS) surface ocean drifters (23 January to 29 April). The RV Ronald H. Brown conducted in situ and remote sensing measurements of oceanic and atmospheric properties with an emphasis on mesoscale oceanic–atmospheric coupling and aerosol–cloud interactions. In addition, the ship served as a launching pad for Wave Gliders, Surface Wave Instrument Floats with Tracking (SWIFTs), and radiosondes. Details of measurements made from the RV Ronald H. Brown, ship-deployed assets, and other platforms closely coordinated with the ship during ATOMIC are provided here. These platforms include Saildrone 1064 and the RAAVEN UAS as well as the Barbados Cloud Observatory (BCO) and Barbados Atmospheric Chemistry Observatory (BACO). Inter-platform comparisons are presented to assess consistency in the data sets. Data sets from the RV Ronald H. Brown and deployed assets have been quality controlled and are publicly available at NOAA's National Centers for Environmental Information (NCEI) data archive (https://www.ncei.noaa.gov/archive/accession/ATOMIC-2020, last access: 2 April 2021). Point-of-contact information and links to individual data sets with digital object identifiers (DOIs) are provided herein.
The Ron Brown cruise during ACE‐Asia (March–April 2001) encountered complex aerosol that at times was dominated by marine, polluted, volcanic, and dust aerosols. Average total light scattering ...coefficients (σsp for Dp <10 μm, relative humidity (RH) = 19%, and λ = 550 nm) ranged from 23 (marine) to 181 Mm−1 (dust). Aerosol hygroscopicity ranged from deliquescent with hysteresis (marine frequently and polluted variably) to hygroscopic without hysteresis (volcanic) to nearly hygrophobic (dust‐dominated). Average deliquescence and crystallization RH were 77 ± 2% and 42 ± 3%, respectively. The ambient aerosol was typically on the upper branch of the hysteresis loop for marine and polluted air masses and the lower branch for dust‐dominated aerosols. Average f(RH = ambient), defined as σsp (RH = ambient)/σsp (RH = 19%), ranged from 1.25 (dust) to 2.88 (volcanic). Average h(RH ∼60%), defined as f(RH)upper branch/f(RH)lower branch, were 1.6, 1.3, 1, and 1.25 for marine, polluted, volcanic, and dust, demonstrating an importance of hysteresis to optical properties. Hemispheric backscatter fraction (b) at ambient RH ranged from 0.077 (marine) to 0.111 (dust), while single scattering albedo (ω) at ambient RH ranged from 0.94 (dust and polluted) to 0.99 (marine).
There has been considerable debate about the relative importance of sea-salt and sulphate from non-sea-salt sources in determining aerosol radiative effects in the marine boundary layer. In the ...marine boundary layer, the most numerous aerosols are volatile sulphate particles smaller than about 0.08 µm (ref. 1) and most of the aerosol mass is in a few sea-salt particles larger than 1 µm. Yet intermediate-size aerosols between about 0.08 and 1 µm diameter are the most relevant to the radiative forcing of climate because they efficiently scatter solar radiation and also serve as cloud nuclei. Indeed, Charlson et al. hypothesized that oceanic production of sulphate aerosols from the oxidation of dimethyl sulphide could be a powerful feedback in the climate system. It is generally assumed that marine aerosols smaller than about 1 µm are non-sea-salt sulphate, but a recent review cites indirect evidence that many aerosols in the sub-micrometre range contain at least some sea-salt,. Here we present direct observational evidence from a remote Southern Ocean region that almost all aerosols larger than 0.13 µm in the marine boundary layer contained sea-salt. These sea-salt aerosols had important radiative effects: they were responsible for the majority of aerosol-scattered light, and comprised a significant fraction of the inferred cloud nuclei.
To analyze the association of polymorphisms in the tau gene with pathologically confirmed corticobasal degeneration (CBD).
The authors previously described an extended tau haplotype (H1) that covers ...the human tau gene and is associated with the development of progressive supranuclear palsy (PSP). The authors now extend this analysis to CBD, a neurodegenerative condition with clinical and neuropathologic similarities to PSP. Like PSP, CBD is associated with accumulation of aggregates containing the 4-repeat isoforms of tau. Because of difficulty in diagnosis of CBD, the authors only analyzed cases with pathologically confirmed CBD.
The authors collected 57 unrelated, neuropathologically confirmed cases of CBD. Tau sequencing in these cases failed to show the presence of pathogenic mutations. Polymorphisms that spanned the tau gene were analyzed in all CBD cases and controls.
Analyzing tau polymorphisms in CBD cases showed that the frequency of H1 and H1/H1 was significantly increased when analyzing all cases and when separating by country of origin. H1 frequency in all CBD cases was 0.921, compared with a control frequency of 0.766 (X(2) = 9.1, p = 0.00255 1df, OR 3.56 8.43 > CI 95% > 1.53). The H1/H1 frequency was also significantly higher at 0.842 compared with 0.596 in age-matched controls (X(2) = 17.42, p = 0.00016, 2df), OR 3.61 7.05 > CI 95% > 1.85).
The CBD tau association described here suggests that PSP and CBD share a similar cause, although the pathogenic mechanism behind the two diseases leads to a different clinical and pathologic phenotype.
Measurements during recent field campaigns downwind of the Indian subcontinent, Asia, and the northeastern United States reveal a substantial decrease in the relative humidity dependence of light ...scattering, fσsp(RH), with increasing mass fraction of particulate organic matter (POM) for submicrometer aerosol. Using data from INDOEX (INDian Ocean EXperiment), ACE Asia (Aerosol Characterization Experiment – Asia), and ICARTT (International Consortium for Atmospheric Research on Transport and Transformation), we have identified, within measurement limitations, the impact of POM on the fσsp(RH) of accumulation mode sulfate‐POM mixtures. The result is a parameterization that quantifies the POM mass fraction ‐ fσsp(RH) relationship for use in radiative transfer and air quality models either as input or as validation. The parameterization is valid where the aerosol consists of an internally mixed sulfate‐carbonaceous accumulation mode and other externally mixed components (e.g. sea salt, dust) and is applicable on both global and regional scales.
Results are presented from 3 years of simultaneous measurements of aerosol chemical composition and light scattering and absorption at Barrow, Alaska. All results are reported at the measurement ...relative humidity of ≤ 40%. Reported are the annual cycles of the concentration of aerosol mass, sea salt, non‐sea‐salt (nss) sulfate, methanesulfonate or MSA−, NH4+, and nss K+, Mg+2, and Ca+2 for the submicron and supermicron size ranges. Submicron nss SO4=, NH4+, and nss K+, Mg+2, and Ca+2 peak in winter and early spring corresponding to the arrival and persistence of Arctic Haze. Submicron sea salt displays a similar annual cycle presumably due to long‐range transport from the northern Pacific Ocean. Supermicron sea salt peaks in summer corresponding to a decrease in sea ice extent. Submicron and supermicron MSA− peak in the summer due to a seasonal increase in the flux of dimethylsulfide from the ocean to the atmosphere. A correlation of MSA− and particle number concentrations suggests that summertime particle production is associated with this biogenic sulfur. Mass fractions of the dominant chemical species were calculated from the concentrations of aerosol mass and chemical species. For the submicron size range the ionic mass and associated water make up 80 to 90% of the aerosol mass from November to May. Of this ionic mass, sea salt and nss SO4= are the dominant species. The residual mass fraction, or fraction of mass that is chemically unanalyzed, is equivalent to the ionic mass fraction in June through October. For the supermicron size range the ionic mass and associated water make up 60 to 80% of the aerosol mass throughout the year with sea salt being the dominant species. Also reported for the submicron size range are the annual cycles of aerosol light scattering and absorption at 550 nm, Ångström exponent for the 450 and 700 nm wavelength pair, and single scattering albedo at 550 nm. On the basis of linear regressions between the concentrations of sea salt and nss SO4= and the light scattering coefficient, sea salt has a dominant role in controlling light scattering during the winter, nss SO4= is dominant in the spring, and both components contribute to scattering in the summer. Submicron mass scattering efficiencies of the dominant aerosol chemical components (nss SO4=, sea salt, and residual mass) were calculated from a multiple linear regression of the measured light scattering versus the component concentrations. Submicron nss SO4= mass scattering efficiencies were relatively constant throughout the year with seasonal averages ranging from 4.1 ± 2.9 to 5.8 ± 1.0 m2 g−1. Seasonal averages for submicron sea salt ranged from 1.8 ± 0.37 to 5.1 ± 0.97 m2 g−1 and for the residual mass ranged from 0.21 ± 0.31 to 1.5 ± 1.0 m2 g−1. Finally, concentrations of nss SO4= measured at Barrow were compared to those measured at Poker Flat Rocket Range, Denali National Park, and Homer for the 1997/1998 and 1998/1999 Arctic Haze seasons. Concentrations were highest at Barrow and decreased with latitude from Poker Flat to Denali to Homer revealing a north to south gradient in the extent of the haze.
A major objective of the Indian Ocean Experiment (INDOEX) involves the characterization of the extent and chemical composition of pollution outflow from the Indian Subcontinent during the winter ...monsoon. During this season, low‐level flow from the continent transports pollutants over the Indian Ocean toward the Intertropical Convergence Zone (ITCZ). Traditional standardized aerosol particle chemical analysis, together with real‐time single particle and fast‐response gas‐phase measurements provided characterization of the sampled aerosol chemical properties. The gas‐ and particle‐phase chemical compositions of encountered air parcels changed according to their geographic origin, which was traced by back trajectory analysis. The temporal evolutions of acetonitrile, a long‐lived specific tracer for biomass/biofuel burning, number concentration of submicrometer carbon‐containing particles with potassium (indicative of combustion sources), and mass concentration of submicrometer non‐sea‐salt (nss) potassium are compared. High correlation coefficients (0.84 < r2 < 0.92) are determined for these comparisons indicating that most likely the majority of the species evolve from the same, related, or proximate sources. Aerosol and trace gas measurements provide evidence that emissions from fossil fuel and biomass/biofuel burning are subject to long‐range transport, thereby contributing to anthropogenic pollution even in areas downwind of South Asia. Specifically, high concentrations of submicrometer nss potassium, carbon‐containing particles with potassium, and acetonitrile are observed in air masses advected from the Indian subcontinent, indicating a strong impact of biomass/biofuel burning in India during the sampling periods (74 (±9)% biomass/biofuel contribution to submicrometer carbonaceous aerosol). In contrast, lower values for these same species were measured in air masses from the Arabian Peninsula, where dominance of fossil fuel combustion is suggested by results from single‐particle analysis and supported by results from gas‐phase measurements (63 (±9))% fossil fuel contribution to submicrometer carbonaceous aerosol). Results presented here demonstrate the importance of simultaneous, detailed gas‐ and particle‐phase measurements of related species when evaluating possible source contributions to aerosols in different regions of the world.
The triple isotopic composition of oxygen in sulfate and nitrate, and the sulfur isotopic composition of the sulfate fine fraction, have been measured on size‐segregated aerosol samples collected at ...Trinidad Head, coastal California, alongside the ITCT‐2k2 campaign in April–May 2002. The isotopic anomaly Δ17O = δ17O − 0.52 × δ18O has been determined in both sulfate and nitrate and was used as a specific tracer of the formation pathways of these species. Coarse mode sulfate in all samples exhibited a small but significant Δ17O anomaly indicating either uptake or in situ formation of secondary sulfate on sea spray. Non‐sea‐salt sulfate Δ17O in the coarse fraction is consistent with (1) either primarily coagulation of finer sulfate particles, when Δ17O is low in all size fractions, or (2) ozone‐driven oxidation of SO2 within the sea spray, as observed in the relatively higher Δ17O in coarse particles compared to fine. It is proposed that triple‐isotope measurements of sulfate oxygen can be used to quantify the budget of in situ sea spray nss‐SO4 formation. The Δ17O measured in size‐resolved nitrate revealed, for the first time, differences in the nitrate formation budget as a function of particle size in a given air mass. The coarse particle nitrate possessed a higher Δ17O, suggesting a relatively larger N2O5 hydrolysis contribution to the nitrate formation budget compared to fine particles where homogeneous formation is more important. We conclude that the complete isotope ratio analysis may provide a basis for future modeling of the formation and transformation processes of the soluble aerosol, based on direct observation of the mechanisms.
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