Characterization of aerosol hygroscopicity, mixing state, and CCN activity at a suburban site in the central North China Plain

Abstract

Abstract. This study investigates aerosol hygroscopicity, mixing state, and cloud condensation nucleation as part of the Atmosphere–Aerosol–Boundary Layer–Cloud Interaction Joint Experiment performed in the summer of 2016 at Xingtai (XT), a suburban site located in the center of the North China Plain (NCP). In general, the probability density function (PDF) of the hygroscopicity parameter (κ) for 40–200 nm particles had a unimodal distribution, and mean κ-PDF patterns for different sizes were similar, suggesting that the particles were highly aged and internally mixed because of strong photochemical reactions. The κ calculated from the hygroscopic growth factor in the daytime and at night suggests that photochemical reactions largely enhanced the aerosol hygroscopicity. This effect became weaker as the particle size increased. In addition, the aerosol hygroscopicity was much larger at XT than at other sites in the NCP. This is because new particle formation takes place much more frequently in the central NCP, which is heavily polluted from industrial activities, than elsewhere in the region. The evolution of the planetary boundary layer played a dominant role in dictating aerosol mass concentration. Particle size was the most important factor influencing the ability of aerosols to activate, whereas the effect of chemical composition was secondary, especially when supersaturation was high. Using a fixed value of κ=0.31 to calculate the cloud condensation nuclei number concentration in this region suffices.

Distinct Ultrafine‐ and Accumulation‐Mode Particle Properties in Clean and Polluted Urban Environments

“…The H‐TDMA system used in this study was custom built (Tan et al, ; Y. Wang, Li, et al, ). Briefly, this system mainly includes two differential mobility analyzers (DMA, model 3081L, TSI Inc.) and a water‐based condensation particle counter (WCPC, model 3787, TSI Inc.).…”

“…The H‐TDMA can measure the GF probability distribution function (GF‐PDF) for particles with a specified diameter. Detailed information on the aerosol hygroscopicity conveyed in the measurements of the H‐TDMA can be used to study aerosol sources (Y. Wang et al, ; Xie et al, ). This is because the GF‐PDF pattern depends on aerosol chemical composition and the mixing state, both of which are highly related to aerosol formation and aging processes (Liu et al, ; Wang et al, ).…”

A New Method for Distinguishing Unactivated Particles in Cloud Condensation Nuclei Measurements: Implications for Aerosol Indirect Effect Evaluation

“…The sampling site has a high aerosol background value (H. , which could cause a significant deviation in the counting rate of the DMT-CCNC owing to water depletion (Deng et al, 2011), making measured N CCN lower than actual N CCN (Wang et al, 2018). One end of the black carbon tube was extended out of the laboratory, and the other was connected to the instrument to measure the ambient atmosphere.…”

Retrieval of Cloud Condensation Nuclei Number Concentration Profiles From Lidar Extinction and Backscatter Data

“…In reality, the uncertainty of using the mean value of κ to estimate the CCN number concentration varies with atmospheric conditions. Most studies show that the uncertainty is within 10% (Deng et al, ; Jurányi et al, ; Wang et al, ). The hygroscopicity parameter κ describes the relationship between the particle dry diameter and CCN activity when compositional data are not available (Petters & Kreidenweis, ).…”

“…The hygroscopicity parameter κ describes the relationship between the particle dry diameter and CCN activity when compositional data are not available (Petters & Kreidenweis, ). Wang et al () found that the sensitivity of the estimated CCN concentration to κ depends strongly on the variability of the shape of the aerosol size distribution. The sensitivity of CCN concentration to κ becomes weaker with increasing supersaturations, suggesting that chemical composition becomes less important in CCN concentration estimates at larger supersaturations .…”