Over the past decades, Beijing, the capital city of China, has encountered increasingly frequent persistent haze events (PHEs). Severe PHEs not only lead to a sharp decrease in visibility, causing traffic hazards and disruptions, and, hence, affecting economic activities, but also induce serious health problems such as respiratory illnesses and heart disease. While the increased pollutant emissions serve as the most important reason, changes in regional atmospheric circulation associated with large-scale climate warming are found to play a role as well.
