Abstract: For better understanding the distribution and variation characteristics of atmospheric ice nuclei (IN) concentration at different altitudes,an aircraft observational experiment was carried out over Shenyang and its surrounding areas from April to September in 2011 and 2012.The analysis results show that the values of IN number concentration in the near-surface layer at Shenyang range from 10¹ to 10² L^-1 in the range of air temperature between -15 and -20 ℃,and the background concentration of IN at different altitudes (1.5- 4.5 km) in clouds are less than 2.0 L^-1 and 10.0 L^-1,respectively.The spatial distribution and temporal variation of atmospheric IN in the near-surface layer and in clouds over Liaoning and Shenyang areas have large variability,with 1-2 order of magnitude in the difference between the maximum and minimum concentrations.The IN number concentration decreases gradually with increasing height below 4.5 km.The vertical distribution of the number concentration of natural IN that has not been affected by artificial catalysis follows a power function well,while the IN number concentration increases by an order of magnitude at least observed in clouds at 3.1 km after distributing silver iodide as the artificial catalyst.The IN number concentration detection corresponds to a water-surface supersaturation of -1.0% to 5.0%,and the ice formation process includes the deposition and condensation-freezing nucleation mechanisms.

Key words: Atmospheric ice nuclei, Aircraft sampling, Static diffusion cloud chamber, Artificial precipitation