Abstract. Cirrus clouds typically form in the upper troposphere and play an important role in the Earth's energy balance and the atmospheric water cycle. This study utilizes DARDAR-Nice data within June to August from 2006 to 2016 (except 2011), combined with CloudSat cloud products and other related aerosol products, to analyze the distribution characteristics and some possible formation mechanisms of ice crystal number concentration (Ni) in cirrus clouds over the Tibetan Plateau (TP). The results indicate that Ni over the northern TP is generally lower than that over the southern TP. This contrast shows a certain connection with differences in aerosol occurrence and the intensity of convective activity between the two regions. The vertical distribution of Ni over the TP exhibits a V-shaped structure. When deep convective activity occurs, Ni tends to increase at the same altitude compared to non-convective conditions. In contrast, under dust- and smoke-influenced conditions, Ni is generally lower, which may be related to ice formation via heterogeneous nucleation. In addition, weak vertical motion near 400 hPa over the northern TP is linked to an earlier appearance of the Ni peak at altitudes below the homogeneous freezing threshold temperature (−38 °C).
Wang et al. (Tue,) studied this question.