The meteorological and environmental conditions for pollution flashover events in Eastern China

Eastern China, as one of the most polluted and populated regions, plays an important role in the economic development of China. The rapid economic growth in this region has boomed China's economy for the past few years. However, due to the industrialization and urbanization in this area, more and more pollutants have been emitted into the atmosphere, which inevitably brings serious problems of air pollution. In this study, the meteorological and environmental conditions for pollution flashover events in Eastern China are analyzed from MERRA-2 (second Modern-Era Retrospective analysis for Research and Applications) meteorological (temperature, relative humidity, wind speed and direction and pressure) and aerosol (aerosol optical depth and particle mass concentration) products, combined with flashover frequency measurements in recent 40 years. It shows that AOD (aerosol optical depth) is higher in the northern part of Eastern China than the southern part, which is similar to the spatial distribution of occurrence rate of pollution flashover in this region. The occurrence rate of pollution flashover is higher in winter than the other seasons, especially for large-area flashover. The less precipitation, lower boundary layer height and higher particle mass concentration near surface contribute a lot to the higher flashover events in winter. For the temporal variation, it shows a relative higher occurrence rate of flashover in 1990s, which corresponding to the rapid increasing period of aerosol optical depth. The blooming up of industrial manufacture and the southward moving of industrial center in this period due to the reform and opening-up policy made more particle pollutants emitted to the air in the Eastern China. The higher loading of aerosol and more dense power grid resulted in more frequent occurrence of flashover events in Eastern China in this period. With the more advance technology of insulator and stricter environment protection policy, the occurrence of flashover events decreases in recent few years. In general, the long-term high loading of aerosols, less precipitation, more occurrences of fog and haze events and high relative humidity are the main causes for the occurrence of pollution flashover in the power grid.