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.

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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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Visibility is a crucial parameter for aeronautical operations. Forward‐scatter meters are recommended to measure it because of inherent advantages. With wide use at airports, the substitutability among forward‐scatter meters is worth paying attention to, especially in low‐visibility environments. To confirm the substitutability among forward‐scatter meters, eight kinds of forward‐scatter meters were installed in an indoor atmospheric environment simulation chamber. The observed values of each of the eight forward‐scatter meters in haze and smoke low‐visibility environments were collected. By least‐squares fitting analysis and the ATE/LER zones method, in the haze, the two sets of CS125 can be substituted for each other in visibilities lower than 2000 m. PWD20 and V30 can be substituted for each other at visibilities lower than approximately 1200 m. From 1200 to 2000 m, the consistency of the two instruments is poor. In the smoke, CS125 and PWD20 display good substitutability with each other when visibility is less than 2000 m. If only focusing on visibilities less than approximately 1000 m, the VPF‐710 and V30 instruments can be substituted with each other.

A dense fog on 28 Nov 2011 in Tianjin region is simulated and diagnosed with WRF model. A reasonable of micro-physical processes and parameters of the program is selected in the simulation .The results showed that: the selected WRF program can simulate the whole process of the fog .The key reasons about the formation of fog are below: strong warm vapor transportation and the plenty of local atmospheric vapor, a strong low-level temperature advection , the weak convergence of vapor decrease the temperature, below 850hpa the following continued weak wind and atmospheric stratification stability that created a stable circumstance. This fog is one typical advection and radiation fog. With near-surface strong wind, especially around 850hpa cold advection cooling the temperature of high place and turbulent transport and moisture divergence of weak sinking motion warming the temperature of lower place, the progress destroyed the atmosphere stable stratification. The fog weakened and dissipated. advection ；weather analysis ; Ⅰ INTRODUCTION Fog is one local weather phenomena. The formation and dissipation of fog can be affected not only by the large-scale weather systems but also by local topography, local radiation and turbulence, atmosphere aerosols, gravity sedimentation and the composition of microscopic particle in the air. Fog is a severe common weather in China will seriously reduce visibility. Heavy fog cause great harm to aviation, high way and marine transportation. In fog, hazes of pollutants suspended in air for a long time is not easy to spread, this will result in air pollution and do harmful to man's health. Economic losses and casualties caused by fog have increased year by year. To carrying out research and forecasting of fog on people's lives and property is significant. For fog, the difficulty lies in the lack of fog detection research data and the lack of continuous monitoring of a long process of fog, especially the lack of the detection equipment of liquid water content of fog and wind speed vertical structure. So far, research and analysis of the fog is broadly divided into two areas: statistical analysis and numerical simulation. Statistical analysis is to find out the macroscopic characteristics which the same types of fog occurs with same regional background and climate characteristics. Mao etc. analyzed and calculated the relationship of some meteorological elements between the distribution of fog and frequency fog occurs. Chen etc. statistic of seasonal and diurnal variation of the fog. Zhou etc. statistic of annual and decadal variations and the relationship between atmospheric humidity and turbidity. These studies have yielded many useful conclusions about the formation and dissipation of the fog. Compared with statistical methods, numerical simulation take full account of the micro-physical processes, the interaction between the dynamical process and thermal process, Many domestic and foreign scholars have done a lot of research about the occurrence, development, and dissipation mechanisms o...