Abstract:

Based on an aircraft observation of a warm cloud in Taiyuan, Shanxi province on August 31, 2018, we analyzed the vertical distribution and causes of the number concentration (N_c) and spectral dispersion (ε) of cloud droplet.The results show that N_c and ε vary complexly with altitude, and their vertical distributions are mainly affected by vertical velocity, inversion zone, and clamp coil in clouds.When the upwelling (or downwelling) increases (weakens) with height, both ε and N_c increase, and show a positive correlation with each other.When there is a maximum of upwelling or downwelling, the upwelling is easy to produce collision coalescence growth, and N_c decreases with the increase of height and has a negative correlation with ε.However, the downwelling promotes aerosol reactivation and then makes cloud droplets increase and has a negative correlation with ε.The thickness and intensity of the inversion zone affect the vertical distribution of ε and the correlation between N_c and ε in the inversion zone and its upper cloud area.When the inversion layer is thicker, ε decreases with the increase in height, and N_c and ε are positively related.Inversely, when the inversion layer is thin, ε increases with the increase of height, and N_c and ε are negatively related.The upper cloud in the inversion area is not saturated, and the cloud droplet is evaporated, both N_c and ε decrease with increasing height and are positively correlated.The entrainment near the cloud top makes N_c decrease with the increase in height, and there is a positive correlation between N_c and ε.

Key words: Dispersion, Vertical velocity, Entrainment, Inversion zone