Measurements of key chemical and physical parameters made along continuous and selected long sections of polar ice cores provide reliable past snow accumulation rates and other environmental records. The prime accumulation indicators include variations found in the stable isotopes, ionic constituents, and acidity concentration levels; and physical changes in the strata and structure. Cross correlations of the time series curves resulting from multiparameter analyses of ice cores from Antarctica (NBY89, SP78, BS68) and Greenland (CR74, D3 81, D3 18C) have been made. The results permit construction of a bipolar chemical stratigraphy chronology of volcanic events that is coherent with the δ ¹⁸O and Electrical Conductivity Method data sets and consistent back‐in‐time with historically recorded volcanic activity. A bihemispheric comparison of high non‐sea‐salt SO₄²⁻ peaks shows strong correlation at 1885, 1836, 1816, 1810, 1459, 1346, 1287, 1278, 1259, 1228, and 1168 A.D. at time of snow deposit. The prominent 1259 A.D. volcanic signal appears to be a significant bipolar ice core index horizon.

Tethered balloon-borne aerosol measurements were conducted at Syowa Station, Antarctica during the 46th Japanese Antarctic expedition (2005–2006). The CN concentration reached a maximum in the summer, although the number concentrations of fine particles (D_p>0.3 μm) and coarse particles (D_p>2.0 μm) increased during the winter–spring. The CN concentration was 30–2200 cm⁻³ near the surface (surface – 500 m) and 7–7250 cm⁻³ in the lower free troposphere (>1500 m). During the austral summer, higher CN concentration was often observed in the lower free troposphere, where the number concentrations in fine and coarse modes were remarkably lower. The frequent appearance of higher CN concentrations in the free troposphere relative to continuous aerosol measurements at the ground strongly suggests that new particle formation is more likely to occur in the lower free troposphere in Antarctic regions. Seasonal variations of size distribution of fine-coarse particles show that the contribution of the coarse mode was greater in the winter–spring than in summer because of the dominance of sea-salt particles in the winter–spring. The number concentrations of fine and coarse particles were high in air masses from the ocean and mid-latitudes. Particularly, aerosol enhancement was observed not only in the boundary layer, but also in the lower free troposphere during and immediately after Antarctic haze events occurring in May, July and September.

We verified an algorithm using multi-wavelength Mie-Raman lidar (MMRL) observations to retrieve four aerosol components (black carbon (BC), sea salt (SS), air pollution (AP), and mineral dust (DS)) with in-situ aerosol measurements, and determined the seasonal variation of aerosol components in Fukuoka, in the western region of Japan. PM_2.5, PM₁₀, and mass concentrations of BC and SS components are derived from in-situ measurements. MMRL provides the aerosol extinction coefficient (α), particle linear depolarization ratio (δ), backscatter coefficient (β), and lidar ratio (S) at 355 and 532 nm, and the attenuated backscatter coefficient (β_att) at 1064 nm. We retrieved vertical distributions of extinction coefficients at 532 nm for four aerosol components (BC, SS, AP, and DS) using 1α₅₃₂ + 1β₅₃₂ + 1β_att,1064 + 1δ₅₃₂ data of MMRL. The retrieved extinction coefficients of the four aerosol components at 532 nm were converted to mass concentrations using the theoretical computed conversion factor assuming the prescribed size distribution, particle shape, and refractive index for each aerosol component. MMRL and in-situ measurements confirmed that seasonal variation of aerosol optical properties was affected by internal/external mixing of various aerosol components, in addition to hygroscopic growth of water-soluble aerosols. MMRL overestimates BC mass concentration compared to in-situ observation using the pure BC model. This overestimation was reduced drastically by introducing the internal mixture model of BC and water-soluble substances (Core-Gray Shell (CGS) model). This result suggests that considering the internal mixture of BC and water-soluble substances is essential for evaluating BC mass concentration in this area. Systematic overestimation of BC mass concentration was found during summer, even when we applied the CGS model. The observational facts based on in-situ and MMRL measurements suggested that misclassification of AP as CGS particles was due to underestimation of relative humidity (RH) by the numerical model in lidar analysis, as well as mismatching of the optical models of AP and CGS assumed in the retrieval with aerosol properties in the actual atmosphere. The time variation of lidar-derived SS was generally consistent with in-situ measurement; however, we found some overestimation of SS during dust events. The cause of this SS overestimation is mainly due to misclassifying internally mixing DS as SS, implying that to consider internal mixing between DS and water-soluble substances leads to better estimation. The time-variations of PM_2.5 and PM₁₀ generally showed good agreement with in-situ measurement although lidar-derived PM_2.5 and PM₁₀ overestimated in dust events.

High PM_2. 5 concentrations of around 100 µg m⁻³ were observed twice during an intensive observation campaign in January 2015 at Fukuoka (33.52° N, 130.47° E) in western Japan. These events were analyzed comprehensively with a regional chemical transport model and synergetic ground-based observations with state-of-the-art measurement systems, which can capture the behavior of secondary inorganic aerosols (SO₄²⁻, NO₃⁻, and NH₄⁺). The first episode of high PM_2. 5 concentration was dominated by NO₃⁻ (type N) and the second episode by SO₄²⁻ (type S). The concentration of NH₄⁺ (the counterion for SO₄²⁻ and NO₃⁻) was high for both types. A sensitivity simulation in the chemical transport model showed that the dominant contribution was from transboundary air pollution for both types. To investigate the differences between these types further, the chemical transport model results were examined, and a backward trajectory analysis was used to provide additional information. During both types of episodes, high concentrations of NO₃⁻ were found above China, and an air mass that originated from northeast China reached Fukuoka. The travel time from the coastline of China to Fukuoka differed between types: it was 18 h for type N and 24 h for type S. The conversion ratio of SO₂ to SO₄²⁻ (F_s) was less than 0.1 for type N, but reached 0.3 for type S as the air mass approached Fukuoka. The higher F_s for type S was related to the higher relative humidity and the concentration of HO₂, which produces H₂O₂, the most effective oxidant for the aqueous-phase production of SO₄²⁻. Analyzing the gas ratio as an indicator of the sensitivity of NO₃⁻ to changes in SO₄²⁻ and NH₄⁺ showed that the air mass over China was NH₃-rich for type N, but almost NH₃-neutral for type S. Thus, although the high concentration of NO₃⁻ above China gradually decreased during transport from China to Fukuoka, higher NO₃⁻ concentrations were maintained during transport owing to the lower SO₄²⁻ for type N. In contrast, for type S, the production of SO₄²⁻ led to the decomposition of NH₄NO₃, and more SO₄²⁻ was transported. Notably, the type N transport pattern was limited to western Japan, especially the island of Kyushu. Transboundary air pollution dominated by SO₄²⁻ (type S) has been recognized as a major pattern of pollution over East Asia. However, our study confirms the importance of transboundary air pollution dominated by NO₃⁻, which will help refine our understanding of transboundary heavy PM_2. 5 pollution in winter over East Asia.