Photosynthetic performance was investigated using photosynthesis-irradiance curve experiments conducted during shipboard observations in the western North Pacific. Surface photosynthetic parameters exhibited substantial variability, with maximum photosynthetic rates ranging from 2.33 to 8.46 mg C [mg chl-a]−1 h−1, and initial light-limited slopes ranging from 0.015 to 0.044 mg C [mg chl-a]−1 h−1 (μmol photons m−2 s−1)−1. A significant linear relationship between these parameters was observed in oligotrophic subtropical waters where environmental variability was minimal, indicating that variations in primary productivity were closely linked to physiological responses of phytoplankton. Analysis of rainfall events suggested that nitrogen limitation was temporarily alleviated by sporadic allochthonous inputs, such as atmospheric wet deposition of reactive nitrogen, prior to seawater sampling. This interpretation was further evaluated through additional shipboard observations under pre- and post-rainfall conditions. Photosynthetic parameters were enhanced following an episodic rainfall event, and estimated daily primary production increased from 4.5 mg C m−3 d−1 under pre-rainfall conditions to 6.5 mg C m−3 d−1 under post-rainfall conditions, representing a 1.4-fold increase. Based on the measured concentrations of reactive nitrogen in rainwater, the observed enhancement in carbon fixation could be quantitatively supported by atmospheric wet deposition. This observational study demonstrates that rainfall is an important source of allochthonous nutrients in oligotrophic marine environments and that rain-derived reactive nitrogen deposition can exert a significant influence on primary productivity.

The deposition of nutrients from the atmosphere into the ocean has been recognized as an important pathway for marine ecosystems. We measured the photosynthetic rates of phytoplankton for surface seawater sampled at three sites with nitrogen-nutrient-depleted condition in the subtropical, western North Pacific in March 2021 during the R/V Mirai cruise using a photosynthesis-irradiance experiment, to investigate the impact of atmospheric inorganic nitrogen deposition. The maximum photosynthetic rates at the Sites 1 (25-00°N, 145-00°E), 2 (26-30°N, 135-00°E), and 3 (28-00°N, 135-17°E) were 5.56±0.15, 6.91±0.17 and 7.38±0.15 mg-C (mg-Chl-a)-1 h-1, respectively. We estimated the atmospheric deposition fluxes of inorganic nitrogen to be 6.3±0.9, 12.7±2.2 and 21.2±3.3 µmol-N m-2 during the 24 h before the seawater sampling at Sites 1, 2, and 3, respectively, using the regional chemical transport model. The primary production fluxes estimated from the simulated inorganic nitrogen deposition flux assuming the all bioavailable with the Redfield ratio corresponded well the changes in the potential production of the surface seawater based on the measured maximum photosynthetic rates and Chlorophyll-a concentration at each site. These findings highlight the role of atmospheric inorganic nitrogen deposition in sustaining primary production in nutrient-depleted subtropical western North Pacific.

Changes in the physical and biogeochemical conditions of the ocean over time can affect marine ecosystems. In this study, we use biogeochemical observational data for the past 25 years (1999–2023) to investigate ocean acidification and changes in biological production at site K2 (47˚ N, 160˚ E) in the western subarctic region of the North Pacific Ocean. During this period, satellite-derived sea surface temperatures increased at a rate of 0.056 °C yr–1, while the surface mixed-layer salinity decreased by 0.004 yr−1. As a result of the oceanic uptake of anthropogenic CO2 from the atmosphere, the deseasonalized annual mean surface mixed-layer pH and saturation states of calcium carbonate minerals of calcite and aragonite decreased at rates of 0.0013 ± 0.0004, 0.007 ± 0.003, and 0.004 ± 0.002 yr−1, respectively. These rates are consistent with those calculated for winter. Under these acidification conditions, no significant trends were observed in either the annual mean or winter concentrations of nutrients (phosphate, nitrate, and silicate), or in total alkalinity in the surface mixed layer. However, the decadal trends in nutrient concentrations show a significant increase in May and decrease in July. Net community production (NCP), which is an index of biological production, was estimated from differences in nutrient concentrations between winter and May or July. This analysis revealed significant decreasing trends in NCP from winter to May, followed by increasing trends from winter to July. The stoichiometric molar ratio of Si associated with the July NCP increase (P:N:Si = 1:15:55) is higher than the previously reported ratio (1:16:40). A significant decreasing trend in satellite-derived photosynthetically active radiation (PAR) was observed in May (0.20 ± 0.08 yr−1), which may be linked to reduced biological production during that month. This decrease may be offset by increased production in summer that is likely due to a shift in the timing of the diatom bloom. These findings highlight the effects of long-term changes of potential drivers of both atmospheric and deep oceanic origin on oceanic biological production.

Aerosols act as ice nucleating particles (INPs) in mixed-phase clouds and cause uncertainties in climate prediction of the Arctic, which is warming faster than the global average. Primary biological aerosols (PBAs) are important INPs; however, their spatiotemporal variability, sources, and ice nucleation microphysics remain poorly understood. Here, we performed microscopic analysis, online and offline observations, and model simulations to investigate ambient aerosol particles related to INPs collected during the R/V Mirai Arctic cruise in 2022. We found that PBAs, particularly spores, were transported from terrestrial sources in Alaska and Canada to the Arctic Ocean and contributed to elevated INP concentrations. In addition, the ice-nucleating efficiency of PBAs was suppressed when fresh sea salt attached to or coated INPs. This study reveals an additional source of INPs over the Arctic Ocean, highlights the importance of alterations in INP mixing state during transport. These findings improve understanding of PBA contributions to Arctic cloud formation and their implications for climate feedbacks.

Brown carbon aerosols (BrC) significantly contribute to regional climate warming in East Asia. However, their sources and atmospheric transformation remain poorly constrained due to limited observations. In this study, we clarified the seasonal dynamics of BrC and quantified the sources of relating carbonaceous components, at the gateway of the East Asian air outflow for seasonal variations. Our findings reveal that fossil fuel combustion dominates the sources of BrC containing carbonaceous components in winter, while biomass burning and local biogenic sources become more prominent in spring and summer, respectively. We provide benchmark optical properties of BrC for climate model simulations, demonstrating that the absorption coefficient and mass absorption cross-section of water-soluble fraction from land-originated air masses (0.47 Mm-1 and 0.53 m2 gC-1, respectively) are more than twice those of sea-originated air masses (0.11 Mm-1 and 0.21 m2 gC-1, respectively). Additionally, we show that BrC undergoes photochemical degradation during transport with a half-life of approximately 1.2 days. A significant reduction in BrC levels during the COVID-19 lockdown period highlights the potential of stringent emission controls to mitigate air pollution and its associated climate impacts. By shedding light on the seasonal dynamics, diverse sources, and atmospheric ageing of BrC, the study provides valuable insights for emission reduction strategies and improving BrC representation in climate models.

Iodine chemistry exerts a nonnegligible influence on tropospheric ozone depletion over oceanic regions. The impact of iodine has been extensively studied using three-dimensional chemical transport models (CTMs). However, the factors governing the variability of iodine monoxide (IO) and ozone in the marine boundary layer (MBL) remain uncertain. This study examines the impact of fine-scale meteorological variability and ozone-independent iodine sources on the MBL IO and ozone concentrations over the Western Pacific Warm Pool (WPWP) through ship-borne observations and high-resolution CTMs during November–December 2014. The high (0.56 ^∘ )-resolution model demonstrates a negative correlation between IO and ozone at the observation locations ( r = - 0.45), which is more closely aligned with that derived from the ship-borne observation data ( r = - 0.70) than the coarse (2.8 ^∘ )-resolution model ( r = 0.08). Sensitivity analysis indicates that a contrast in the correlation between the 0.56 ^∘ and 2.8 ^∘ resolutions emerges from the interplay of fine-scale atmospheric transport and chemistry processes, rather than from fine-scale atmospheric transport solely or ozone-dependent oceanic iodine release. This interplay leads to a greater ozone loss mediated by the iodine cycle at 0.56 ^∘ resolution (by 0.56 ppbv day ^-1 ) compared to that at 2.8 ^∘ resolution (by 0.20 ppbv day ^-1 ), due to the reduced mixing with air outside the MBL over the WPWP at finer resolution. Furthermore, incorporating ozone-independent iodine sources such as photolysis of CH_2I_2 , CH_2IBr , and CH_2ICl enhances the IO-ozone anti-correlation coefficient (−0.50). These findings highlight the critical roles of interplay of the fine-scale atmospheric transport and chemistry processes and oceanic ozone-independent iodine sources in the co-variability of IO and ozone over the WPWP.

Light-absorbing organic aerosols (BrC) play a significant role in Earth's climate, but their sources and optical properties remain unclear. We investigated seasonal variations and source-specific contributions to BrC in the Asian outflow region, focusing on Fukue Island, a gateway from the continent to the North Pacific. We conducted parallel analyses of BrC light absorption and organic aerosol composition over a year. We found that BrC levels were markedly higher during winter-spring, coinciding with air masses carrying emissions from Asian sources. Water-soluble BrC absorption exhibited a strong correlation with a specific marker for fossil fuel combustion, suggesting its significant influence on BrC levels. Biomass burning emissions, as indicated by another marker, contributed to BrC levels, particularly in spring. The fraction of BrC soluble in methanol was significantly higher during summer, suggesting potential contributions from additional sources, such as local biogenic emissions, present in air masses from this period. This study sheds light on the seasonal dynamics and source-specific light absorption characteristics of BrC in the Asian outflow region. Our findings contribute to a better understanding of BrC sources and their impact on climate.

Studying tropospheric ozone over the remote areas of the planet, such as the open oceans and the polar regions, is crucial to understand the role of ozone as a global climate forcer and regulator of atmospheric oxidative capacity. A focus on the pristine oceanic and polar regions complements the available land-based datasets and provides insights into key photochemical and depositional loss processes that control the concentrations and spatiotemporal variability in ozone as well as the physicochemical mechanisms driving these patterns. However, an assessment of the role of ozone over the oceanic and polar regions has been hampered by a lack of comprehensive observational datasets. Here, we present the first comprehensive collection of ozone data over the oceans and the polar regions. The overall dataset consists of 77 ship cruises/buoy-based observations and 48 aircraft-based campaigns. The dataset, consisting of more than 630 000 independent ozone measurement data points covering the period from 1977 to 2022 and an altitude range from the surface to 5000 m (with a focus on the lowest 2000 m), allows systematic analyses of the spatiotemporal distribution and long-term trends over the 11 defined ocean/polar regions. The datasets from ships, buoys, and aircraft are complemented by ozonesonde data from 29 launch sites or field campaigns and by 21 non-polar and 17 polar ground-based station datasets. The datasets contain information on how long the observed air masses were isolated from land, as estimated by backward trajectories from the individual observation points. To extract observations representative of oceanic conditions, we recommend using a subset of the data with an isolation time of 72 h or longer, from the analysis with coincident radon observations. These filtered oceanic and polar data showed typically flat diurnal cycles at high latitudes, whereas daytime decreases in ozone (11 %-16 %) were observed at lower latitudes. The ship/buoy- and aircraft-based datasets presented here will supplement the land-based ones in the TOAR-II (Tropospheric Ozone Assessment Report Phase II) database to provide a fully global assessment of tropospheric ozone. The described dataset is available at 10.17596/0004044 (Kanaya et al., 2025).

We conducted intensive atmospheric observations and surface seawater sampling in the western tropical Pacific aboard R/V Mirai during the MR21-03 cruise from May to July 2021 to investigate iodine variations and photochemistry over the global sea surface temperature (SST) maxima (warm pool). Consistent with previous studies, high near-surface atmospheric iodine monoxide (IO) mixing ratios of up to ~ 1 pptv were observed. A strong positive correlation ( r = 0.95) was found between the IO mixing ratios and inorganic iodine flux calculated from atmospheric ozone (O 3 ) and sea surface I – data, indicating that the assumed emission flux and the associated processes are qualitatively reasonable for the studied warm pool region. This study provided the first simultaneous observations of atmospheric O 3 , IO, and sea surface I – over the warm pool, thus demonstrating the robust nature of the relationship. The CHASER chemical transport model satisfactorily reproduced the observed positive correlation. The model overestimated the IO levels by 40%, but large systematic uncertainties were associated; refining the assumed emission flux and parameters used in the model is recommended for more quantitative comparisons. The collective findings underscore the significance of concurrent observations of atmospheric O 3 , IO, and sea surface iodide for elucidating ocean–atmosphere processes involving reactive iodine compounds.

Forest wildfires in interior Alaska represent an important black carbon (BC) source for the Arctic and sub-Arctic. However, BC observations in interior Alaska have not been sufficient to constrain the range of existing emissions. Here, we show our observations of BC mass concentrations and carbon monoxide (CO) mixing ratios in the Poker Flat Research Range (65.12° N, 147.43° W), located in central Alaska, from April 2016 to December 2020. The medians, 10th percentile ranges, and 90th percentile ranges of the hourly BC mass concentration and CO mixing ratio throughout the observation period were 13, 2.9, and 56 ng m−3 and 124.7, 98.7, and 148.3 ppb, respectively. Sporadically large peaks in the BC mass concentration and CO mixing ratio were observed at the same time, indicating influences from common sources. These BC peaks coincided with peaks at other comparative sites in Alaska, indicating large BC emissions in interior Alaska. Source estimation by FLEXPART-WRF (Flexible Particle Dispersion–Weather Research and Forecast) confirmed a contribution of boreal forest wildfires in Alaska and western Canada when high BC mass concentrations were observed. For these cases, we found a positive correlation (r=0.44) between the observed BC/ΔCO ratio and fire radiative power (FRP) observed in Alaska and Canada. This finding implies that the variability of the BC and CO emission ratio is associated with the intensity and time progress of forest wildfires and suggests that the BC emission factor and/or inventory could be potentially improved by FRP. We recommend that FRP be integrated into future bottom-up emission inventories to achieve a better understanding of the dynamics of pollutants from frequently occurring forest wildfires under the rapidly changing climate in the Arctic.

Ice-nucleating particles (INPs) significantly influence aerosol-cloud precipitation interactions at regional and global scales. However, information regarding the concentrations and origins of INPs over the open ocean, particularly at high latitudes, remains insufficient due to access difficulties. In this study, we investigated the concentrations and origins of INPs over the western North Pacific to the Arctic Ocean through ship-borne observations conducted in the early autumn of 2016. The number concentrations of INPs (N-INPs) active at -25 degrees C (N-INPs(-25 degrees C)) and -15 degrees C (N-INPs(-15 degrees C)) varied from 0.034 to 41.2 L-1 and <0.0005 to 0.11 L-1, respectively, and those over the Arctic Ocean (>= 70 degrees N) were the lowest. Comparisons of the observed N-INPs variation with chemical compositions and autofluorescent properties of ambient aerosol particles indicated that N-INPs(-25 degrees C) and N-INPs(-15 degrees C) were largely influenced by mineral and biological materials of terrestrial origin, respectively. We further observed higher N-INPs over the Bering Sea and the Northwestern Pacific (40-60 degrees N) at the return cruise than those at the outward cruise. Aerosol composition and backward trajectory analyses indicated that particles originating from Siberian wildfires could significantly contribute to the observed high N-INPs. These results suggest a substantial role of boreal wildfires in supplying INPs onto the oceans, including high latitudes, depending on the transportation and emission conditions.

Brown carbon (BrC) aerosols play a significant role in atmospheric radiative forcing, particularly in the Arctic where they could potentially contribute to surface warming. However, their regional variability and sources in the open ocean remain poorly understood. To address this, we conducted ship-based aerosol measurements aboard the R/V Mirai during the MR18-05C research cruise (October–December 2018), spanning the western North Pacific, Bering Sea, and Arctic Ocean. We examined BrC optical properties alongside PM 2.5 chemical composition, trace gases, and meteorological conditions to assess its variability and sources. Our results reveal a drastic northward decline in BrC levels, with light absorption capability in the Bering Sea and the Arctic approximately 50% lower than those in the western North Pacific. The strongest BrC absorption was observed in regions influenced by crop residue burning in Northeast China. In the Arctic, BrC remained low as the main footprint is within the Arctic alongside limited BrC sources, although occasionally affected by long-range transport. Chemical composition analysis highlights biomass burning and fossil fuel emissions as dominant BrC sources in the western North Pacific. Solubility analysis indicated that BrC in the Arctic was predominantly water soluble, increasing its susceptibility to wet scavenging. A strong high-pressure system (1027 ± 6.2 hPa) over the Arctic (November 9–17) led to aerosol accumulation, although BrC remained low. This study underscores the complex interplay between regional emissions, long-range transport, and atmospheric processing in regulating BrC distributions across latitudinal gradients. Our findings highlight the importance of source-region emissions and transport pathways in determining BrC fate in the Arctic, with implications for understanding its role in climate forcing.

Aerosols have substantial impacts on climate change and marine ecosystems over the northwestern Pacific Ocean (NWPO); however, their spatiotemporal variability and characteristics have not been sufficiently characterized especially in the East Asian winter monsoon. The compositions and physical parameters of fine-mode aerosols over the NWPO were investigated during a cruise on the research vessel Mirai in the late winter and early spring of 2021. Ship-based high-temporal resolution observations and laboratory analyses of aerosol number concentrations and chemical and elemental compositions revealed the diverse sources and transport processes significantly affecting the behavior of fine-mode aerosol particles in the marine boundary layer (MBL) over the NWPO. The number concentrations of aerosol particles with mobility diameters greater than 100 nm, which were used as a proxy for cloud condensation nuclei (CCN), were generally positively correlated with black carbon and sulfate concentrations throughout the cruise, indicating that even in remote oceans, higher CCN number concentrations were significantly associated with non-natural sources. Latitudinal contrasts in fine-mode aerosol compositions were observed between the subarctic (> 35°N) and subtropical (< 30°N) regions. In the subarctic region, sea-salt (SS) aerosols were dominant in fine-mode mass under windy conditions (up to approximately 30 m s−1) and their mass concentration variations were well explained by the MBL structure and wind–wave conditions. In the subtropical regions, in contrast, the CCN proxy number concentrations and mass concentrations of non-SS aerosols (sulfate, carbonaceous, and metallic components) were elevated due to synoptic-scale transport of continental air masses. As ammonium sulfate was a dominant component in the subtropical regions over the NWPO, the observed enhancement of aerosol concentrations substantially impacted CCN concentrations in this region where is far (1000–1500 km) from continental source regions in Southeast and East Asia. Additionally, volcanic emissions of sulfur compounds contributed significantly to the enhancement of sulfate aerosol mass and particle number concentrations near Nishinoshima, which was not in an eruptive state during the cruise. These results highlight the significances and further requirements of in situ ship-based characterizations to better understand aerosol physicochemical properties and processes, such as sea-spraying emission, in the MBL over the NWPO.

Abstract. Studying tropospheric ozone over the remote areas of the planet, such as the open oceans and the polar regions, is crucial to understand the role of ozone as a global climate forcer and regulator of atmospheric oxidative capacity. A focus on the pristine oceanic and polar regions complements the available land-based data sets and provides insights into key photochemical and depositional loss processes that control the concentrations, spatio-temporal variability of ozone, and the physico-chemical mechanisms driving these patterns. However, an assessment of the role of ozone over the oceanic and polar regions has been hampered by a lack of comprehensive observational data sets. Here, we present the first comprehensive collection of ozone data over the oceans and the polar regions. The overall data set consists of 77 ship cruises/buoy-based observations and 48 aircraft-based campaigns. The data set, consisting of more than 630,000 independent ozone measurement data points covering the period from 1977 to 2022 and an altitude range from the surface to 5000 m (with a focus on the lowest 2000 m), allows systematic analyses of the spatio-temporal distribution and long-term trends over the defined 11 ocean/polar regions. The data sets from ships, buoys, and aircrafts are complemented with an ozonesonde data set from 29 launch sites or field campaigns, and by 21 non-polar and 17 polar ground-based stations data sets. The data were filtered by using backward trajectories calculated with the HYSPLIT model from the individual observation points to extract essentially oceanic observations, defined as air masses that have travelled over oceans for 72 hours or more, which were further tested with the coincident Radon observations. The oceanic and polar data thus selected showed typically flat diurnal patterns at high latitudes and daytime decreases (11–16 %) at low latitudes, indicating the adequacy of the data collection and processing procedures, as well as the potential for further studies of processes with statistical robustness and coverage. The ship/buoy- and aircraft-based data sets presented here will supplement the land-based ones in the TOAR-II database to provide a fully global assessment of tropospheric ozone.

Black carbon (BC) aerosol, released into the atmosphere from fuel combustion and biomass burning, is known to be an important short-lived climate forcer (SLCF) because it efficiently absorbs solar radiation and directly heats the atmosphere. Because its accumulation on snow and ice promotes their melting, BC is an important driver of warming, particularly in the Arctic region. Observed surface BC concentrations in the Arctic region show typical seasonal variations, increasing during the winter and spring and decreasing during the warmer season with some peak events in few months of summer, along with large interannual variations. The present study investigates the primary factors influencing the differences in the spatiotemporal surface concentrations of BC in the Arctic region by performing a hemispheric-scale air-quality simulation for the years 2015 and 2016. The model reasonably simulates the observed BC concentration levels and their seasonal patterns, as well as their differences between these two years. This study shows that large year-to-year variability in BC-rich air-mass pathways, such as long-range transport from surrounding regions, and besides these air-mass stagnation within the Arctic region, influence the differences in the Arctic BC concentrations between 2015 and 2016. In addition, the Arctic BC concentrations were also controlled by interannual variations in the amount and distribution of emissions due to the size and the location of open fires, including both Asian crop residue burning in spring and boreal forest fires in summer.

We investigated the association of marine biological indicators (polysaccharides, protein-like gel particles, and chl a) with the formation of fluorescent aerosol particles, cloud condensation nuclei (CCNs), and ice-nucleating particles (INPs) over the North Pacific Ocean, Bering Sea, and Arctic Ocean during September–November 2019. The abundance of bioindicators was high in the North Pacific Ocean and the Bering Sea (e.g., up to 1.3 mg m−3 of chl a), suggesting high biological activity due to a phytoplankton bloom. In the North Pacific Ocean, particles were characterized by high mass fractions of organics and sulfate with a predominance of terrestrial air masses. Conversely, in the Bering Sea and the Arctic Ocean, particles were characterized by high mass fractions of sea salt and sulfate with a predominance of maritime air masses. The averaged range/value of the CCN concentration at 0.4 % supersaturation were 99–151, 43–139, and 36 cm−3 over the North Pacific Ocean with terrestrial influences, over the Bering Sea with marine biogenic influences, and over the Arctic Ocean with marine influences, respectively, and the corresponding range/value of the hygroscopicity parameter κ were 0.17–0.59, 0.42–0.68, and 0.66, respectively. The averaged INP concentration (NINP) measured at temperatures of −18 and −24 ∘C with marine sources in the North Pacific and Bering Sea was 0.01–0.09 and 0.1–2.5 L−1, respectively, and that over the Arctic Ocean was 0.001–0.016 and 0.012–0.27 L−1, respectively. When marine sources were dominant, fluorescent bioaerosols in the fine mode were strongly correlated with all bioindicator types (R: 0.81–0.88) when the effect of wind-induced uplift from the sea surface to the atmosphere was considered. Correlations between NINP measured at −18 and −24 ∘C and all bioindicator types (R: 0.58–0.95 and 0.79–0.93, respectively) were positive, even when the extreme outlier point was omitted, as were those between NINP and fluorescent bioaerosols (R: 0.50 and 0.60, respectively), suggesting that marine bioindicators contributed substantially as sources of bioaerosols and to cloud formation.

Severe PM2.5 air pollution over the Asian continent is occasionally transported across the East China Sea by the westerly winds to Japan, continuing for long distances over the Pacific Ocean. Despite such polluted air masses causing health issues, conventional models tend to underestimate levels of organic aerosols (OA) and PM2.5. Here, PM2.5 and its major components recorded during three field campaigns carried out at Fukue Island (32.75°N, 128.68°E), Japan (spring 2009), Rudong (32.25°N, 121.37°E), China (spring 2010), and Jeju (33.35°N, 126.39°E), Korea (autumn 2012) around the East China Sea were used to test the performance of the Weather Research and Forecasting-Chem/ATRAS-MOSAIC model. Overall, model performance was improved by introducing chemical aging represented by a volatility basis-set scheme, whereby median values of the model/observation ratio for OA were raised to 0.34–1.28 from 0.30–0.35 in the case of conventional settings. In particular, the levels of OA at the Fukue site and daytime buildup of the OA levels at all three sites were reproduced by the model. OA levels were still sometimes underestimated. This suggests that either emission rates of organic precursors are being underestimated or other pathways of OA formation are also important. Our analysis also indicates that this region is characterized by high OH concentrations, promoting chemical aging. The predictions of PM2.5 levels in the model also improved, with median values of the model/observation ratio shifting from 0.67–0.91 to 0.68–0.95, when chemical aging of OA was taken into account.

Asian continental outflow air masses reach western Japan in the springtime, carrying high levels of ozone produced over the Asian continent, and facilitating in-situ production. In this study, in-situ production was highlighted; the rate and limiting factors of net ozone production were diagnosed at Fukue Island, a remote island west of Japan, on 17 days during May–June 2009, when the continental outflow air mass arrived, using an observation-based modeling approach. The average ozone production was estimated to be 6.8 ppb per day. Information on the chemical status of the arriving air mass is important, because it affects how further ozone production in the air mass occurs after precursor addition from Japanese domestic emissions. The main limiting factor of ozone production for such air masses was usually nitrogen oxides (NOx), suggesting that domestic NOx emission control is important in reducing further ozone production. Volatile organic compounds (VOCs) also increased the ozone production rate, and occasionally (14

Marine aerosol feedback on biogeochemical cycles and the climate remains highly uncertain due to the complex interplay. This review highlights recent advances in our understanding of organic aerosols, nitrogen, and iron as well as cloud properties over the Pacific Ocean.