Diurnal variations of atmospheric electric fields on fair weather days and its correlations with aerosols, wind speed, irradiance, and relative humidity.

The atmospheric electric field (AEF) is an important electrical phenomenon that occurs between the Earth's surface and the ionosphere. It is primarily formed by negative charges on the surface and positive charges in the ionosphere, and is regulated by multiple factors, such as solar activity, meteorological conditions, and air pollution. On the basis of AEF's observational data from fair weather days in the Chenggong district of Yunnan, this study analyzes its daily variation trends, focusing on its correlations with the air quality indicator concentrations of PM2.5 and PM10, solar irradiance and meteorological parameters. The results indicate that the daily average variation in the AEF presents a typical "W" shape, During the period from 00:00 to 08:00, AEF exhibits a strong positive correlation with PM2.5 and maximum wind speed. From 08:00 to 17:00, AEF shows a strong positive correlation with solar irradiance. Between 17:00 and 23:00, AEF demonstrates a strong positive correlation with PM2.5, PM10, and relative humidity (RH), and a strong negative correlation with maximum wind speed. At night, when there is no irradiance, the increase in PM2.5 and PM10 concentrations leads to a significant increase in the AEF. We believe this is due to aerosol particles adsorbing charged ions from the air, which decreases the local conductivity and causes an increase in the AEF. During the day, from 08:00 to 17:00, the changes in the AEF are synchronous with solar irradiance, both of which exhibit a trend of first increasing and then decreasing. This is attributed primarily to the enhanced atmospheric thermal convection and turbulence caused by irradiance, which drive fluctuations in near-surface water vapor and aerosol concentrations, leading to a gradual increase in the AEF from 08:00 to 12:00. Subsequently, from 12:00 to 17:00, as the irradiance and PM2.5 concentrations decline, the decrease in aerosol concentrations results in a corresponding reduction in the atmospheric electric field. This study provides strong evidence for more deeply understanding the relationship between aerosol concentrations and the near-surface AEF.