Numerical simulation research on the effects of atmospheric ice nuclei based on observations on the convective cloud microphysical processes and precipitation in North China

Atmospheric ice nuclei play a crucial role in the occurrence and development of convective cloud precipitation. This paper is based on the collaborative observation of ice nucleation and aerosols in North China, and constructs a parameterized formula for ice nucleation that conforms to the actual characteristics of North China. The parameterization description of ice nucleation in the SBM scheme of the WRF model is improved, and then are used to simulate typical convective cloud precipitation processes in North China. The results show that the simulated convective cloud with the modified scheme has stronger upward airflow and is closer to the actual situation; Under the action of updrafts, atmospheric ice nuclei are transported to the middle and upper layers of clouds and cloud anvils, increasing the number of ice crystals in the upper atmosphere through processes such as heterogeneous nucleation, ultimately leading to an increase in surface rainfall intensity and total rainfall. In addition, the three heterogeneous ice formation mechanisms of atmospheric ice nuclei, namely contact freezing, condensation/sublimation freezing, and immersion freezing, occur in different temperature ranges and dominate at different heights; When the concentration of atmospheric ice nuclei increases, the formation rates of the three heterogeneous nuclei increase synchronously and are more competitive compared to homogeneous freezing of cloud droplets. High concentrations of atmospheric ice nuclei lead to an increase in heterogeneous nucleation processes, an increase in the mass concentration of ice crystals and snow, and the consumption of cloud water by heterogeneous nucleation leads to a decrease in graupel and rainwater.