Estimation of Aerosol Activation Ratio and Water Vapor Supersaturation at Cloud Base Using Aircraft Measurement

On November 13, 2016, under the background of continuous and stable stratiform cloud weather over Beijing area, the vertical observation of aerosol particle size spectrum, chemical composition, cloud droplet spectrum and other parameters was carried out by aircraft to study the cloud bottom aerosol in this case. Activation ability. The results show that during the detection period, the Beijing area was slightly polluted, and the surface aerosol concentration (0.11～3μm) reached 4600 cm-3. The cloud height was 800～1200 m, and the number of aerosols at the cloud base was significantly greater than that of the near ground. The effective particle size is significantly increased (0.3~0.6μm). At the same time, the hydrophobic primary organic aerosol in the near-ground aerosol contributes significantly, while the contribution of the primary organic aerosol in the cloud bottom aerosol is greatly reduced, and the inorganic components and The contribution of secondary organic aerosols has increased significantly, causing the hygroscopicity parameter κ to increase from 0.25 (ground) to 0.32 (cloud bottom). The spectral distributions of cloud aerosols and cloud droplets are well connected, and the number concentration of the two The sum is consistent with the cloud bottom aerosol concentration, which can respectively represent unactivated and activated particles. Based on the cloud bottom aerosol particle size spectrum and hygroscopicity parameters, the activation rate of cloud condensation nuclei under different supersaturation ratios is calculated, and the cloud condensation nucleus activation rate is obtained through observation with the cloud. The results are compared, and the cloud base supersaturation is about 0.048%.