Increasing attention has been given to aerosols due to their substantial influence on the atmospheric environment,clouds and precipitation,and the climate.Atmospheric aerosols can serve as condensation nuclei for the formation of both cloud droplets and ice nuclei,and can alter the microphysical properties of clouds,which in turn affects the formation of rain,snow and other forms of precipitation.Many studies have been performed with the goal of furthering our understanding of the physical,chemical and optical properties of aerosol particles,along with their effects on cloud,precipitation and other weather phenomena.However,large uncertainties still remain in the study of the aerosol particles,in particular the vertical distributions of aerosols found in the lower troposphere.Therefore,there is a need to better understand aerosol vertical distributions.In addition,to better understand the impact of aerosols on clouds,it is crucial to determine the relationships between aerosols and cloud condensation nuclei(CCN).Aerosol particles which act as CCN,and their interactions with cloud droplets are the key uncertainties in determining the effects of aerosols on climate.Although researches including observations near the ground and many extensive aircraft measurements have previously focused on the activation properties of aerosols and CCN,more direct and long-term observations are required to simultaneously characterize height-resolved aerosol,CCN and clouds properties,as well as to provide essential validation for modeling and satellite remote sensing.Using the aircraft as the observation platform by which to carry the instruments can effectively solve these problems.In the present study,in-situ aircraft measurements of aerosols and CCN of 11 flights during the spring and summer of 2010 in the Shijiazhuang area were analyzed,including the comparison of the vertical distribution of aerosol particles,particle size distribution at different heights,and the vertical distribution and activation characteristics of CCN under both cloudy and clear conditions.The results show that the mean aerosol number concentration(N_a) under cloudy conditions is 1 553.28 cm^-3,and the mean effective diameter (D_e) is 0.52 μm,which is 76% larger than that of clear sky (N_a:883.82 cm^-3) and 41% for effective diameter (D_e:0.37 μm).Under cloudy conditions,N_a decreases exponentially with height,and the particle effective radius (R_e) does not change significantly at heights below 2 500 m,however it increases gradually at heights greater than 2 500 m.Under clear sky,N_a accumulates in the height range of 800 to 1 500 m,while R_e does not change significantly with height.The shapes of the aerosol number size distributions remain almost the same at different heights,and have a successive distribution for smaller particles (<0.3 μm) under both cloudy and clear skies,with a sharp decrease at 0.3 μm.Above 2.5 km,N_a is lower under cloudy sky than clear sky,while in the near-surface layer and boundary layer N_a is higher under cloudy sky than clear sky.For both skies,the number concentration of CCN (N_CCN) decreases with altitude at each observation height,and is higher under cloudy sky than clear sky.The activation ratio of CCN(N_CCN/N_CN) does not change significantly with height under cloudy conditions,however it increases with altitude under clear sky.Particle size and N_CCN/N_CN have a positive linear correlation.