Multi-year observations of aerosol microphysical and optical properties, obtained through ground-based remote sensing at 50 China Aerosol Remote Sensing Network (CARSNET) sites, were used to characterize the aerosol climatology for representative remote, rural, and urban areas over China to assess effects on climate. The annual mean effective radii for total particles (R_effT) decreased from north to south and from rural to urban sites, and high total particle volumes were found at the urban sites. The aerosol optical depth at 440 nm (AOD_440 nm) increased from remote and rural sites (0.12) to urban sites (0.79), and the extinction Ångström exponent (EAE_{440–870 nm}) increased from 0.71 at the arid and semi-arid sites to 1.15 at the urban sites, presumably due to anthropogenic emissions. Single-scattering albedo (SSA_440 nm) ranged from 0.88 to 0.92, indicating slightly to strongly absorbing aerosols. Absorption AOD_440 nm values were 0.01 at the remote sites versus 0.07 at the urban sites. The average direct aerosol radiative effect (DARE) at the bottom of atmosphere increased from the sites in the remote areas (−24.40 W m⁻²) to the urban areas (−103.28 W m⁻²), indicating increased cooling at the latter. The DARE for the top of the atmosphere increased from −4.79 W m⁻² at the remote sites to −30.05 W m⁻² at the urban sites, indicating overall cooling effects for the Earth–atmosphere system. A classification method based on SSA_440 nm, fine-mode fraction (FMF), and EAE_{440–870 nm} showed that coarse-mode particles (mainly dust) were dominant at the rural sites near the northwestern deserts, while light-absorbing, fine-mode particles were important at most urban sites. This study will be important for understanding aerosol climate effects and regional environmental pollution, and the results will provide useful information for satellite validation and the improvement of climate modelling.

From the viewpoint of earth system science, this paper discusses the observation capability of the second-generation of Chinese polar-orbiting, sun-synchronous operational meteorological satellite observation systems, Fengyun-3 (FY-3), based on the function and performance test results from the FY-3D satellite observation system in orbit. The FY-3 series of satellites have numerous remote sensing instruments and a wide range of imaging and sounding electromagnetic spectrometers onboard. These instruments can obtain reflectivity data for land surface, soil, vegetation, water body, snow cover, ocean color, and sea ice on earth’s surface over a wide spectral range, as well as information on the absorption and scattering radiative transfer of molecules and particles (clouds and aerosols) in earth’s atmosphere. All of these data can be used to retrieve physical and chemical information about the land, ocean, and atmosphere of the earth system. Comprehensive observation of the earth system by the FY-3 meteorological satellites is preliminarily realized.

Himawari-8 (H8), as a geostationary satellite, observing the full disk image of the earth per 10 min, is a very powerful tool to investigate atmospheric aerosol temporal variations. The advanced himawari imager (AHI) onboard H8 has several spectral bands similar with those of Moderate Resolution Imaging Spectroradiometer (MODIS). Aerosol optical depth (AOD) is thus possible to be retrieved from AHI data using the dark target (DT) method of MODIS. Based on a statistics study of infrared bands of these two satellite instruments, we found that the difference of shortwave infrared bands between AHI (2.3 μm) and MODIS (2.12 μm) in DT area can be ignored for our purpose. Meanwhile, for AHI sensor, the normalized difference vegetation index (NDVI) calculated from 0.86 μm (instead of traditional 1.24 μm) and 2.3 μm can also be a good indicator of surface spectral reflectance. Therefore, first, a new NDVI of AHI sensor is proposed in this paper to improve the estimation of surface reflectance based on DT retrieval method. Then, AOD over DT area was retrieved using a lookup table strategy and tested based on AHI observation over China region from August 2015 to July 2016. All retrieved results are validated against ground-based measurements of the aerosol robotic network and the sun-sky radiometer observation network. The coincident AOD results between AHI retrieval- and ground-based network measurements show good agreements with R² of 0.81. The intercomparison between AHI and MODIS DT AOD products also shows a good agreement with R² of 0.92.

Satellite observation is an effective way of obtaining global aerosol information. The study focuses on developing a new scheme to apply the traditional dark target (DT) method to the advanced Medium Resolution Spectral Imager (MERSI II), which is a part of the Chinese Fengyun-3-D satellite. Compared with the Moderate Resolution Imaging Spectroradiometer (MODIS), MERSI II shows higher ratios between red (0.65 $\mu \text{m}$ ) and near-infrared ( $2.13~\mu \text{m}$ ) bands in surface reflectance estimation and the green band ( $0.55~\mu \text{m}$ ) that is more sensitive to cloud screening. Aerosol optical depth (AOD) is retrieved from earlier MERSI II observations by following the adapted DT method over land in Asia in 2018. Overall, AOD from MERSI II has a good performance compared with ground-based measurements with an expected error (EE%) of 66.38% and $R^{2}$ of 0.834, which is close to the MODIS EE% of 70.59% and $R^{2}$ of 0.829. Both sensors slightly overestimate the AOD over heavy aerosol loading regions, but MERSI-II has larger retrieval area covering a wider swath than MODIS in heavy hazy areas. On a spatial scale, the MERSI II effectively reflects the AOD distribution pattern but tends to overestimate and underestimate AOD at low and high latitudes, respectively, when compared with MODIS. The MERSI II sensor shows good aerosol detection potential, and the DT algorithm can be applied. MERSI II will provide important observation data on climate change and atmospheric pollution for the investigations in the future.