Deliquescent phenomena of ambient aerosols on the North China Plain

In this study, we report that the deliquescent phenomena of ambient aerosols on the North China Plain are frequently observed using a humidified nephelometer system. The deliquescence relative humidity (RH) primarily ranges from 73 % to 81 %, with an average of 76.8 %. The observed deliquescent phenomena of ambient aerosols exhibit distinct diurnal patterns and are highly correlated with ammonium sulfate. The following scenario is proposed to explain the observed diurnal pattern of deliquescent phenomena: in the late morning, nitrate begins to decrease significantly, whereas ammonium and sulfate change slowly, which leads to an increase in the MR (the MR is defined as the molar ratio of , the results of [Cheung et al., 2015] show that aerosol particles without the hysteresis phenomenon have the lowest MR value) and the emergence of deliquescent behavior. After nitrate reaches its lowest concentration in the afternoon, it increases dramatically, and the ammonium and sulfate contents then remain nearly constant or increase slightly, which causes a decrease in the MR and the gradual cessation of deliquescent behavior. The frequently observed deliquescent phenomena of ambient aerosols in this paper imply that current parameterization schemes that describe the RH dependence of particle light scattering may result in a significant bias when estimating aerosol effects on climate.