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Carbonaceous aerosol particles emitted from biomass burning (BB) have a large impact on the global climate. In particular, tarball particles (TBs), which are spherical organic aerosol particles, account for a large proportion of aerosol particles from BB. In this study, we collected aerosol particles over the western North Pacific and analyzed them using transmission electron microscopy with energy-dispersive X-ray spectroscopy (TEM-EDX) to reveal their shape and composition. We detected TBs and organic carbon particles originating from Siberian forest fires. To the best of our knowledge, this is the first case in which a large number of TBs have been found over the Pacific Ocean far from the BB source. The spherical shapes of the TBs were maintained even after long-range transport. In addition, our individual analysis of TBs showed that the size and composition of TBs differ depending on the air mass origin. The occurrence and microphysical properties of TBs are important to accurately evaluate the impact of TBs on climate. Our results imply that TBs can be transported to the Arctic and have an influence on radiative forcing over the ocean and in the Arctic.

We employed a global high-resolution inverse model to optimize the CH4 emission using Greenhouse gas Observing Satellite (GOSAT) and surface observation data for a period from 2011−2017 for the two main source categories of anthropogenic and natural emissions. We used the Emission Database for Global Atmospheric Research (EDGAR v4.3.2) for anthropogenic methane emission and scaled them by country to match the national inventories reported to the United Nations Framework Convention on Climate Change (UNFCCC). Wetland and soil sink prior fluxes were simulated using the Vegetation Integrative Simulator of Trace gases (VISIT) model. Biomass burning prior fluxes were provided by the Global Fire Assimilation System (GFAS). We estimated a global total anthropogenic and natural methane emissions of 340.9 Tg CH4 yr−1 and 232.5 Tg CH4 yr−1, respectively. Country-scale analysis of the estimated anthropogenic emissions showed that all the top-emitting countries showed differences with their respective inventories to be within the uncertainty range of the inventories, confirming that the posterior anthropogenic emissions did not deviate from nationally reported values. Large countries, such as China, Russia, and the United States, had the mean estimated emission of 45.7 ± 8.6, 31.9 ± 7.8, and 29.8 ± 7.8 Tg CH4 yr−1, respectively. For natural wetland emissions, we estimated large emissions for Brazil (39.8 ± 12.4 Tg CH4 yr−1), the United States (25.9 ± 8.3 Tg CH4 yr−1), Russia (13.2 ± 9.3 Tg CH4 yr−1), India (12.3 ± 6.4 Tg CH4 yr−1), and Canada (12.2 ± 5.1 Tg CH4 yr−1). In both emission categories, the major emitting countries all had the model corrections to emissions within the uncertainty range of inventories. The advantages of the approach used in this study were: (1) use of high-resolution transport, useful for simulations near emission hotspots, (2) prior anthropogenic emissions adjusted to the UNFCCC reports, (3) combining surface and satellite observations, which improves the estimation of both natural and anthropogenic methane emissions over spatial scale of countries.