Spatiotemporal Evolution and Meteorological Drivers of PM2.5 Concentrations in the Yangtze River Delta, China

China has conducted various measures for air pollution control and promptly alleviated major air environmental problems. However, many severe challenges of air pollution, especially PM2.5 pollution, still exist in China. By using the PM2.5 concentration data during the period of 2015–2018 and meteorological data in 2017 of 227 sites in the Yangtze River Delta (YRD), China, trend analysis, Moran's I, and geographically weighted regression were used to investigate the spatiotemporal pattern of PM2.5 concentrations and the spatial variations of meteorological influences on PM2.5 concentrations in the YRD. Results showed that PM2.5 concentrations in the YRD exhibited an overall decreasing trend, with a growth rate of -3.75
$\mu \mathrm{g}/(\mathrm{m}^{3}\cdot \mathrm{a})$
. Obvious regional differences were observed in PM2.5 concentrations, and the high-value areas were concentrated in the northwestern YRD and the low-value areas were mainly distributed in the southeastern YRD. The influences of meteorological factors on PM2.5 in the YRD varied in each season. In winter, wind speed and rainfall negatively affected PM2.5 concentrations. By contrast, sea level pressure, relative humidity, planetary boundary layer height, and temperature positively influenced PM2.5 concentrations.