Monitoring fine particulate matter with diameters of less than 2.5 μm (PM2.5) is a critical endeavor in the Beijing–Tianjin–Hebei (BTH) region, which is one of the most polluted areas in China. Polar orbit satellites are limited by observation frequency, which is insufficient for understanding PM2.5 evolution. As a geostationary satellite, Himawari-8 can obtain hourly optical depths (AODs) and overcome the estimated PM2.5 concentrations with low time resolution. In this study, the evaluation of Himawari-8 AODs by comparing with Aerosol Robotic Network (AERONET) measurements showed Himawari-8 retrievals (Level 3) with a mild underestimate of about −0.06 and approximately 57% of AODs falling within the expected error established by the Moderate-resolution Imaging Spectroradiometer (MODIS) (±(0.05 + 0.15AOD)). Furthermore, the improved linear mixed-effect model was proposed to derive the surface hourly PM2.5 from Himawari-8 AODs from July 2015 to March 2017. The estimated hourly PM2.5 concentrations agreed well with the surface PM2.5 measurements with high R² (0.86) and low RMSE (24.5 μg/m³). The average estimated PM2.5 in the BTH region during the study time range was about 55 μg/m³. The estimated hourly PM2.5 concentrations ranged extensively from 35.2 ± 26.9 μg/m³ (1600 local time) to 65.5 ± 54.6 μg/m³ (1100 local time) at different hours.

China is likely the world's largest anthropogenic source of methane emissions, with coal mine methane (CMM) being the predominant contributor. Here, we deploy 2 years of satellite observations to survey facility‐level CMM emitters in Shanxi, the most prolific coal mining province in China. A total of 138 detected episodic events at 82 facilities are estimated to emit 1.20 (+0.24/−0.20, 95% CI) million tons of methane per year (Mt CH₄/yr) during 2021–2023, roughly equivalent to 4.2 times the integrated flux from the Permian plumes and four times of the integrated flux from the Four Corners plumes, two of the world's largest hotspots for oil and gas methane emissions. This work reveals the heavy‐tailed distribution characteristic of CMM emission sources for the first time, with 20% of emitters contributing approximately 50% of total emissions. Comparison with the Global Energy Monitor (GEM) inventory reveals that the GEM estimate is about 4.1 times our estimate.

The Advanced Himawari Imager (AHI), the primary sensor aboard the Japanese Himawari‐8 geostationary satellite, measures regional aerosol observations with high temporal‐spatial resolution. To improve product quality and scientific applications, we performed a comprehensive evaluation of AHI aerosol products (version 1.0). We compared nearly 2 years (15 July 2015 to 31 June 2017) of AHI aerosol optical depth at 500 nm (AOD500) with AODs from the Aerosol Robotic Network (AERONET) and the Maritime Aerosol Network (MAN). Results showed that, over land, AHI retrievals exhibit a large overall bias of −0.062, with an R of 0.78; over ocean, average bias measured 0.036 (0.051 for MAN), with an R of 0.89 (0.95 for MAN). AHI retrievals collocated with AERONET AODs (τ_A) showed the following expected AHI AOD errors: (−0.66 × τ_A + 0.02, −0.34 × τ_A + 0.16) over land and (−0.24 × τ_A + 0.03, 0.10 × τ_A + 0.11) over ocean. AHI retrievals with degraded performance correlated to different regions, angles, aerosol types, and surface types, suggesting that the AHI aerosol algorithm can be improved by changing aerosol optical models, using better cloud filters, and combining multiple methods to estimate ground reflectance. Collocated comparisons of AHI‐MODerate‐resolution Imaging Spectroradiometer‐AERONET demonstrate that, over land, AHI daytime AODs clearly improve when retrievals with a large viewing zenith angle and small scattering angle are excluded.