Spectral analysis of weekly variation in PM10 mass concentration and meteorological conditions over China

This study investigates the region-dependent anthropogenic weekly variation in air pollutants and its relationship with the meteorological conditions over China for the summers of 2001–2005. Spectral analysis was applied to the local daily observations of PM10 (aerosol particulate matter with a diameter <10 μm) mass concentrations and precipitation from 31 ground stations, reanalysis estimates of regional atmospheric variables, and satellite retrievals of clouds. Our analysis shows that the 6–8-day variance of PM10 concentrations from the periodogram is closely correlated with the mean PM10 concentration, which may depend on the size (population) and geographical setting of a city, its prevailing climatic conditions, and the type/degree of human activities. We define normalized variance as the ratio of the 6–8-day to 2–14-day variance of PM10 concentrations, possibly indicating the relative anthropogenic signal to the noise of natural weather variability. The normalized variance of PM10 concentrations has a distinct regional rainfall distribution from that of the mean PM10 concentration in China. As compared to regions with lower normalized variance of PM10 concentrations, the regions with higher normalized variance generally show higher normalized variance of rainfall events, 1000 hPa wind speeds, sea-level pressure, size spectrum and phase of cloud particles, cloud optical depth, and cloud top pressure. Our results confirm the presence of the interaction between PM10 and the meteorological conditions in the boundary layer, and suggest a possible link of cloud formation to PM10 on a weekly scale.