Ice Particle Habit Classification Method with Improved Thresholds and Its Application

To apply Holroyd’s proposed cloud particle habit classification method to the ice particle measured by airborne cloud imaging probe (CIP) in northern China, this article improves the thresholds in the Holroyd’s cloud particle habit classification based on historical airborne measurement data, which makes the habit classification method more suitable for the ice particle measured by CIP in northern China. The improved threshold method is used to process and analyze the airborne measurement data from a precipitation stratus cloud in Shanxi Province. It is found that there are four types of ice particles with a frequency of occurrence greater than 15% in the vertical and horizontal distribution in this stratiform precipitation cloud; three among them are relatively fixed, namely, graupel, line shape, and irregular type. The fourth type is related to the specific cloud environment. In the vertical direction, it is dendrite (−8 to 0°C) or tiny (−12 to 8°C), and in the horizontal direction of different heights it is dendrite (5200 m) or tiny (5500 m) or plate (5800 m). The concentration of ice particles fluctuates widely in the horizontal and vertical distribution, with a minimum of less than 1 L⁻¹ and a maximum of more than 25 L⁻¹. The maximum values in the vertical distribution are located in the central and lower parts of the cloud. The ice water content in the cloud also fluctuates a lot in the horizontal and vertical direction. The maximum vertical value area in the cloud is basically consistent with the number concentration of ice particles.