[1] Organic molecular compositions of marine aerosol samples, collected at low latitudes to midlatitudes in the Northern Hemisphere during a round-the-world cruise, were studied using gas chromatography/mass spectrometry. More than 140 organic species were detected in the samples and were grouped into different compound classes based on the functionality and sources. The concentrations of total quantified organics ranged from 0.94 to 111 ng m −3 (average of 34 ng m −3 ). Biogenic secondary organic aerosol (SOA) tracers from the oxidation of isoprene (e.g., 2-methyltetrols), a/b-pinene (e.g., pinonic and pinic acids), and b-caryophyllene (b-caryophyllinic acid) were detected in all the samples. Their total concentrations ranged from 0.19 to 27 ng m , which account for 0.48-29% of the total identified organics and 0.05-1.5% of organic carbon in the marine aerosols. The spatial distributions of biogenic SOA tracers exhibited higher loadings over the coastal/tropical regions than the open oceans. In marine aerosols collected over the North Pacific and North Atlantic, the contributions of marine natural emissions (22-33%) were higher than those in the coastal regions (4-14%). Over the tropical regions, atmospheric oxidation products can account for 47-59% of the total organics, with biomass burning emissions of only 1-2%. However, over the western North Pacific, fossil fuel combustion (26%), atmospheric oxidation products (25%), and biomass burning (24%) were the main sources. This study indicates that long-range atmospheric transport of continental aerosols and sea-to-air emission of marine organics, as well as atmospheric oxidation and/or photochemical aging, are important factors controlling the chemical composition of organic aerosols in the marine atmosphere.

Abstract. We intensively observed the atmospheric boundary layer with a polarization lidar, a Sun photometer, and a high-volume sampler at a coastal area of Tokyo Bay. The purpose of the observation is to investigate a phenomenon discovered in the past summer: relatively high depolarization ratio events (•10% at peak) in the lower atmosphere associated with sea breeze. From the chemical analyses of the simultaneously sampled aerosols, we found that the depolarization ratio might be related to crystallized sea salt and dust particles. A boundary structure was clearly revealed by the depolarization ratio in the lower atmosphere, which might correspond to the mixed layer (the internal boundary layer) or the sea breeze in which crystallized sea salt and/or dust particles were diffused. We also presented the first numerical calculation on the depolarization ratio of the cubic particles to apply crystallized sea-salt (NaC1) particles by the dipole discrete approximation (DDA) method: the calculation yields 8-22% of depolarization ratio for the effective size larger than 0.8 •m at the investigated wavelength (532 nm). IntroductionWe have routinely observed the troposphere, mainly to study the atmospheric boundary layer (ABL) (also referred as the planetary boundary layer (PBL)), with a lidar at Tokyo University of Mercantile Marine (TUMM) (35ø40'N, 139ø47'E) since 1993. Our observation site is located in the center of Tokyo and close to Tokyo Bay, as shown in Figure 1. A large amount of aerosols is locally emitted from anthropogenic origins and greatly affects the local air quality and visibility. This site is suited for the study of the urban atmospheric boundary layer, the boundary layer aerosols, the air pollution meteorology, and the sea-land breeze circulation. Aerosols in ABL, except in spring when Asian dust exists, normally dominate the optical thickness of the atmosphere in this area. Therefore the optical property of the aerosols in the urban ABL is one of the most important targets to estimate the direct and indirect effects of the tropospheric aerosols on the radiation budget.The lidar depolarization technique has been extensively applied to cloud research, e.g., to discriminate the phase of clouds (i.e., water or ice clouds) [Sassen, 1991[Sassen, , 1999. However, the application of this technique to the tropospheric aerosol is relatively rare [Sassen, 1999]. We explored the importance of the lidar depolarization technique in the boundary layer me- teorology and characterization of boundary layer aerosols. One of the advantages of the boundary layer study is that we can relate lidar data to meteorological data and in situ measurements of aerosols at the ground level, although the boundary layer aerosols are mixed with various kinds of aerosols and therefore complex. For the upper atmosphere case we need radiosonde observations and airborne sampling of aerosols for a direct comparison with lidar data, which would be highly expensive.In this paper we define the directly observed total depolarization ratio as...

This study investigated spatial distributions of water-soluble dicarboxylic acids and related compounds in the marine aerosols collected at low-to mid-latitudes in the NorthernHemisphere for a better understanding of the photochemical aging of organic aerosols during long-range transport. Their molecular distributions were characterized by the predominance of oxalic acid (C 2 ) followed by malonic (C 3 ) and succinic (C 4 ) acids, except for one sample

[1] Size-segregated measurements of cloud condensation nucleus (CCN) activity and hygroscopic growth were performed simultaneously for sulfate-rich aerosols at Cape Hedo, Okinawa, Japan, in spring 2008. The CCN fractions as functions of particle size at water vapor supersaturations of 0.44%, 0.25%, and 0.10% had nearly stepwise increases, and the diameters for 50% activation of its maximum (d act ) were close to that of (NH 4 ) 2 SO 4 . The size-resolved hygroscopic growth factor g measured using a hygroscopicity tandem differential mobility analyzer at 85% relative humidity (RH) mainly showed unimodal and highly hygroscopic characteristics. The observed characteristics as well as aerosol mass spectrometer data suggest the dominance of internally mixed ammoniated sulfate-rich particles. A clear negative correlation between d act and median g (g median ) was observed for Aitken-mode particles, and backward air mass trajectories indicate lower d act and higher g of the aerosols from China and the Pacific and the opposite tendency for those from Korea and Japan. The size dependence of g median suggests that less hygroscopic carbonaceous components were more enriched in Aitkenmode particles and therefore affect the CCN activity and hygroscopicity. The CCN activation diameters were predicted on the basis of g median using a core-shell model. The modeled activation diameters reasonably agreed with measured d act , suggesting that the surface tension lowering effect due to organics and the enhancement of bulk hygroscopicity at high RH due to sparingly soluble or polymeric compounds were small. The results suggest that CCN activity of sulfate-rich aerosol particles is predicted well in regional and global aerosol models without incorporating these effects.

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[1] Using a single-particle mass spectrometer, the size and chemical composition of individual Fe-containing atmospheric aerosols (Fe aerosols) with diameter from 100 to 1800 nm were characterized during Asian outflow season (spring of 2008) in Okinawa Island, Japan and their sources were determined. Fe aerosols were classified into five unique particle types which were mixed with specific compound(s) and related to their sources (crustal, fly ash/K-biomass burning, elemental carbon, metals, and vanadium). Particle number-based contribution of the crustal particle type, which has been thought to be the main source of aerosol Fe, was quite small (2 ∼ 10%) in all size ranges, while anthropogenic Fe aerosols were the dominant contributor in this study. Fly ash/K-biomass burning type was the most abundant particle types, which contributed ∼50%. Metals and elemental carbon types contributed ∼20% and ∼10%, respectively. Contribution of vanadium type was variable (5 ∼ 50%), which is attributed to ship emission. The frequent appearance of lithium ion peak in the fly ash/K-biomass burning type strongly suggests that large fraction of the type is coal combustion origin, reflecting high coal usage in China. These results show that anthropogenic sources contributes significant portion of Fe aerosols in Asian outflow. Excluding the vanadium type, relative contribution of the remaining four particle types was constant over the course of study, which remained even when the total concentration of Fe aerosols changed and fraction of the Fe aerosols among atmospheric aerosols decreased significantly by the switch of air mass type into marine type. We concluded that the observed constant relative abundance reflected the relative source strength of Fe aerosols in Asian outflow, particularly emphasizing the importance of coal combustion source in East Asia.

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Black carbon (BC) deposited on snow lowers its albedo, potentially contributing to warming in the Arctic. Atmospheric distributions of BC and inorganic aerosols, which contribute directly and indirectly to radiative forcing, are also greatly influenced by depositions. To quantify these effects, accurate measurement of the spatial distributions of BC and ionic species representative of inorganic aerosols (ionic species hereafter) in snowpack in various regions of the Arctic is needed, but few such measurements are available. We measured mass concentrations of size‐resolved BC (CMBC) and ionic species in snowpack by using a single‐particle soot photometer and ion chromatography, respectively, over Finland, Alaska, Siberia, Greenland, and Spitsbergen during early spring in 2012–2016. Total BC mass deposited per unit area (DEPMBC) during snow accumulation periods was derived from CMBC and snow water equivalent (SWE). Our analyses showed that the spatial distributions of anthropogenic BC emission flux, total precipitable water, and topography strongly influenced latitudinal variations of CMBC, BC size distributions, SWE, and DEPMBC. The average size distributions of BC in Arctic snowpack shifted to smaller sizes with decreasing CMBC due to an increase in the removal efficiency of larger BC particles during transport from major sources. Our measurements of CMBC were lower by a factor of ~13 than previous measurements made with an Integrating Sphere/Integrating Sandwich spectrophotometer due mainly to interference from coexisting non‐BC particles such as mineral dust. The SP2 data presented here will be useful for constraining climate models that estimate the effects of BC on the Arctic climate.