Editorial for the Special Issue “Advances in Air Pollution Meteorology”

This Special Issue of the open-access journal Atmosphere, “Advances in Air Pollution Meteorology”, presents papers that highlight important research showing the relationships between meteorology, emissions and air pollutants, including ozone and particulate matter. This Special Issue shows that air pollution is an international problem; therefore, it includes papers that present research from Northeast China, Taiwan, Northeast United States and the United States–Mexico border region in Texas. Meteorology and air quality are strongly related to emissions.

The formation of pollutants such as ozone and particulate matter are affected by the gaseous emissions of nitrogen oxides (NO and NO₂) and volatile organic compounds (VOCs). A paper on evaluating the effects of a clean heating plan on air quality in the Beijing–Tianjin–Hebei Region and a paper on VOCs and their impact on air quality for Southern Taiwan is included. Field measurements of ozone and particulate matter along with meteorological conditions are required to understand their formation and distribution patterns and changes. In this Special Issue, papers on the measurement of black and brown carbon particles and several papers of ozone are included. Analysis of the collected data is critical to understanding and improving air quality. Finally, papers on advanced analysis methods including meteorological and air quality mesoscale modeling, artificial intelligence and sophisticated regression models such as an exponential generalized autoregressive conditional heteroscedasticity (EGARCH) are included in this Special Issue.

The first paper by Lara et al. presents measurements of black and brown carbon made in the Planetary Boundary Layer (PBL) using two photoacoustic extinctiometers [1]. Possible source locations of the particles were evaluated with two models, the High-Resolution Rapid Refresh Smoke model, HRRR, and the Hybrid Single-Particle Lagrangian Integrated Trajectory model, HYSPLIT. A key finding was that wildfires had a strong effect on the background absorption coefficient (Babs) of particles within the (PBL) of the El Paso (US)–Ciudad Juárez (Mexico) airshed, and aging signatures were observed after transport to a different state.

The second paper by Yang et al. presents a comparison of ozone simulations made with the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) for the Chesapeake Bay in the Northeast United States with AirNow ozone measurements [2]. They found that the WRF–Chem model overestimated the local ozone (O₃) concentrations by up to 20–30%. The difference between model simulations and ozone measurements was attributed to differences in the mean bay dynamics circulation-induced contributions during day and night.

The third paper by Wang et al. examines the effects of an emissions reduction program, the Clean Heating Plan, on air quality in the Beijing–Tianjin–Hebei Region of China [3]. In Northern China, much of residential coal combustion of in Northern China has been replaced by centralized electricity generation [3]. Wang et al. used the WRF-Chem model to estimate the effects of this conversion away from residential coal combustion. They found that reductions in particulate matter (PM_2.5 and PM₁₀) would be most significant in local urban regions but less in the surrounding regions. However, meteorological variations had a very large effect on the air quality of this region, and these could be comparable to the effects of emission reduction programs.

The fourth paper by Zhang presents an application of artificial intelligence to evaluate the effects of meteorology on air quality in Beijing [4]. A generalized regression neural network was used to examine how the air quality index (AQI) in Beijing was affected by mean atmospheric humidity, maximum wind velocity, insolation duration, mean wind velocity and the precipitation of rain according to season. A key finding is that the most significant factors affecting the AQI in Beijing were insolation duration, mean atmospheric humidity, and maximum wind velocity.

Karle et al. provided the fifth paper which presents research on the links between atmospheric emissions, circulation patterns, and other meteorological factors on ozone episodes in the El Paso-Juárez airshed, at the Texas border between the United States and Mexico [5]. It was found for this location that anthropogenic and biogenic emissions were a strong factor that influenced ozone concentrations. It was also found that seasonal meteorological variations had a large impact on ozone concentrations too. The key meteorological variables were found to be solar radiation, planetary boundary layer heights and wind flow patterns. The El Paso-Juárez airshed has a complex surface topography and this is shown to have a strong effect on ozone distributions.

Wu and Kuo provided a study of VOCs in Southern Taiwan [6]. They used an exponential generalized autoregressive conditional heteroscedasticity (EGARCH) model to examine ten VOC ozone precursors. The VOCs were measured at monitoring stations in the Kaohsiung–Pingtung area in Taiwan. The regression model identified a number of statistical relationships between individual VOC compounds and the impact of meteorology on their concentrations.

These published papers show that meteorology affects the emissions, formation, concentrations and distribution of ozone and particulate matter. Clear skies that allow greater solar insolation and higher temperatures are associated with higher levels of ozone and particulate matter formation. Analysis tools such as, WRF-Chem, regression models and artificial intelligence are shown to be very useful in estimating these and other factors that affect air quality. We thank all the authors for submitting their exciting and innovative research to this Special Issue of Atmosphere, “Advances in Air Pollution Meteorology”.