Accurate measurements of visibility are of great importance in many fields. This paper reports a multipoint visibility measurement (MVM) method to measure and calculate the atmospheric transmittance, extinction coefficient, and meteorological optical range (MOR). The relative errors of atmospheric transmittance and MOR measured by the MVM method and traditional transmissometer method are analyzed and compared. Experiments were conducted indoors, and the data were simultaneously processed. The results revealed that the MVM can effectively improve the accuracy under different visibility conditions. The greatest improvement of accuracy was 27%. The MVM can be used to calibrate and evaluate visibility meters.

Aerosols can interact with other meteorological variables in the air via aerosol–radiation or aerosol–cloud interactions (ARIs/ACIs), thus affecting the concentrations of particle pollutants and ozone. The online-coupled model WRF-Chem was applied to simulate the changes in the PM2.5 (particulate matter less than 2.5 μm in aerodynamic diameter) and ozone concentrations that are caused by these mechanisms in China by conducting three parallel sensitivity tests. In each case, availabilities of aerosol–radiation interactions and aerosol–cloud interactions were set differently in order to distinguish each pathway. Partial correlation coefficients were also analyzed using statistical tools. As suggested by the results, the ARIs reduced ground air temperature, wind speed, and planetary boundary height while increasing relative humidity in most places. Consequently, the ozone concentration in the corresponding region declined by 4%, with a rise in the local annual mean PM2.5 concentration by approximately 12 μm/m3. The positive feedback of the PM2.5 concentration via ACIs was also found in some city clusters across China, despite the overall enhancement value via ACIs being merely around a quarter to half that via ARIs. The change in ozone concentration via ACIs exhibited different trends. The ozone concentration level increased via ACIs, which can be attributed to the drier air in the south and the diminished solar radiation that is received in central and northern China. The correlation coefficient suggests that the suppression in the planetary boundary layer is the most significant factor for the increase in PM2.5 followed by the rise in moisture required for hygroscopic growth. Ozone showed a significant correlation with NO2, while oxidation rates and radiation variance were also shown to be vitally important.

Aiming at the difficulty in measuring the slant visibility in civil aviation airport, a solution of lidar visibility measurement system is proposed. Semiconductor laser with low pulse energy and high pulse repeat frequency while photodiode detector with the characteristics of low noise and high quanta efficiency have been adopted, which ensure the stability of system works. By using two scanning modes, the flexibility and the measurement accuracy of the system are improved. Experimental results show that the measurement accuracy of the system is better than 20%, which satisfy the requirements of International Civil Aviation Organization.

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