This paper investigates immersion mode ice‐nucleating particle (INP) concentrations measured with a continuous flow diffusion chamber at temperatures of −20°C, −25°C, and −30°C in Beijing from 4 May to 4 June 2018. Aerosol conditions in the experiment period are classified into four types: clean, light PM2.5 pollution, heavy PM2.5 pollution, and dust. The PM mass concentrations and the aerosol size distributions are distinctly different in the four aerosol conditions. INP concentration increases as temperature decreases from −20°C to −30°C for all the four aerosol conditions. At a given temperature, INP concentrations progressively increase as the aerosol condition changes from clean to light PM2.5 pollution and to heavy PM2.5 pollution condition. At −25°C and −30°C, the dust condition has a much higher INP concentration than the other aerosol conditions. The INP concentration is closely related to the number concentration of aerosols with diameters of 1.0–2.5 μm (). Using a similar method as in the previous parameterization of INP concentrations for global and fairly clean aerosol conditions, a new parameterization of the INP concentration based on is provided for the complicated aerosol conditions with high aerosol number concentrations in Beijing.

A series of measurements of ice-nucleating particles (INPs) were performed at two sites in Beijing. At the Beijing Meteorological Service (BMS) site, which was an urban site, no INPs were found to be active above–15°C. However, at the Yanjiaping (YJP) site, which was a rural site, the concentration of INPs active at temperatures above–15°C was found to be as high as 1.73 g^–1. Two parameterizations were constructed by respectively fitting the data obtained at BMS site and YJP site. The two parameterizations, as well as another parameterization from the literature, were implemented into a parcel model to investigate the effect of INPs active above–15°C on phase partitioning in mixed-phase clouds. At a vertical velocity of 0.01 m s^–1, which is typical for stratiform clouds associated with frontal systems, the INPs active above–15°C nucleate ice crystals at low levels. The growth of these ice crystals remarkably reduces both the maximum liquid water mixing ratio and the altitude where the maximum liquid water mixing ratio is reached. When the vertical velocity of the parcel is increased to 0.1 m s^–1 or an even higher value, the evolution of liquid water mixing ratio is not controlled by the INPs active above–15°C but those active below–15°C.

Ice nucleating particles (INPs) can be important for deep convective storms through affecting microphysical, thermodynamical, and radiative properties and precipitation. Since the mass of a hailstone is predominantly contributed by supercooled cloud droplets, INPs in supercooled cloud droplets during deep convective storms can be indicated from INPs in hailstones. In this study, hailstones are collected from eight deep convective cases in three regions of China, and immersion freezing INPs in hailstones are measured using droplet freezing experiments over a wide temperature range from −27.5°C to −4.0°C. INP concentrations can vary by 2–3 orders of magnitude, which is consistent with the result in a previous study on hailstones for the same eight cases that insoluble aerosol number concentrations in hailstones also have a variability of 2–3 orders of magnitude. Using the fitting method, three INP modes are suggested to be included for most hailstone samples, while one to two INP modes can be good enough for a couple of hailstone samples. Furthermore, the INPs for warmer mode are more heat‐sensitive, indicating possible existence of proteinaceous biological species.

There are few studies which reported the characteristics of winter clouds and precipitation in the Haituo Mountains of Northern Beijing where the 2022 Winter Olympic Games will be held. This paper outlines comprehensive datasets, including the surface measurements, remote sensing and aircraft measurements, to study cloud and precipitation characteristics over the mountainous terrain. The analysis results show (1) high-level trough and vortex were the main weather system in all 12 cases. (2) 58% of precipitation occurred only at night, and only 8% of snowfall occurred only at daytime, but under the surface inverse trough snowfall (in 4 of the 12 cases) persisted from night to day peaking at 20 hours; Snowfall persisted at least 3 hours in 83% of the snowfall, 5–10 hours in 50% of cases, and more than 10 hours in 33% of the storms. In 67% of cases, the maximum snowfall occurred within the initial 1-2 hours. (3) In 12 cases, 83% of orographic clouds reached Yan Jiaping, after increased southwesterly winds, resulting in visibility below 100 m. (4) during snowfall, The dominant wind direction is southwest. The start of the snowfall corresponded with an increase in southwesterly wind. The snowfall is maintained according to with the strengthening of southwesterly wind and dissipated accordingly with the receding of southwesterly wind. Whenever the snowfall stopped, the northwest wind was strong at all heights. (5) The first peak value of integral liquid water appeared in the early stage of snow, and we also observed integral liquid water increases with orographic cloud uplift, presenting potentially favorable seeding opportunities in 10 cases. (6) The primary crystal habits collected at Yan Jiaping during steady snowfall were rimed and aggregated planar dendrites.