Diurnal haze variations over the North China plain using measurements from Himawari-8/AHI

Abstract

The diurnal variations of haze properties are essential in understanding the haze pollution formation and its environmental impact. Ground-based measurements can provide this information with high temporal resolution, but the haze measurements are not spatially continuous. The Advanced Himawari Imager (AHI) sensor onboard the next-generation geostationary satellite Himawari-8 can provide haze properties with high spatial and temporal resolution. In this study, the diurnal variations of haze frequency, haze properties [aerosol optical depth (AOD), Angstrom exponent (AE) and fine-particle ratio (RF)] and cloud cover are jointly analyzed over the North China Plain (NCP) for summer and winter seasons during 2015–2017. Both the haze and cloud scheme and the haze properties are well validated. The results reveal that the haze frequency in winter (33.51%) is much higher than that in summer (6.34%), and the diurnal variations of AOD values in winter (0.2–0.9) are stronger than those in summer (0.5–0.9). The diurnal maximum haze frequency values in summer (16:00 p.m.) occur 3 h later than the most severe pollution (13:00 p.m.), with AOD values of 0.7–0.9, AE values of 1.1–1.2 and RF values of 0.5–0.6. In winter, the haze frequency increases from 9:00 to 15:00. However, no typical diurnal variations of AOD, AE and RF are shown. It is also found that haze frequency exhibits opposite diurnal variations compared with those of clouds.