应用气象学报 (Sep 2022)
Weather Conditions and Cloud Microphysical Characteristics of an Aircraft Severe Icing Process
Abstract
Based on the aircraft measurements on 28 February 2021, combined with ERA5 reanalysis data and sounding data, the weather background and the characteristics of cloud structure of a severe icing case on the aircraft are analyzed. The severe icing process is induced by the joint influence of high-level trough, low-level shear line, low-level jet and cold front. The ERA5 reanalysis data show that the maximum value area of supercooled water is mainly distributed at the height of 700 hPa to 600 hPa on the warm side of the front area and the ambient temperature is -4 to -12℃, accompanied by an upward movement of -0.2 to -0.8 Pa·s-1. The sounding data show that the cloud system is distributed in multiple layers. There is a deep dry layer between the upper ice crystal cloud and the lower supercooled water cloud. The temperature in the aircraft detection area is -9 to -3℃ and the dew-point spread is 0℃, which are favorable for icing. During the icing process, the air temperature is -8 to -5℃. Aircraft measurements show that there is abundant supercooled water in clouds. The average liquid water content by cloud particles probe is 0.35 g·m-3, and the maximum value is 0.7 g·m-3. The average liquid water content by total water content measurement probes is 0.5 g·m-3, the maximum value is 0.85 g·m-3, and for 11 minutes the liquid water content is larger than 0.45 g·m-3. The average median volume diameter of cloud particles is 20.3 μm, and the number concentration of cloud particles is 149.3 cm-3 on average. The number concentration of cloud particles tends to increase from low level to high level and vice versa for the median volume diameter of cloud particles. Finally, the conditions with different icing intensity that the King-air 350 aircraft may encounte during weather modification work in the cloud are discussed. The calculation shows that the King-air 350 aircraft carries out observation research or weather modification tasks when the liquid water content in the cloud is higher than 0.04 g·m-3, 0.15 g·m-3 and 0.45 g·m-3, it may encounter light, moderate, and severe icing, under certain conditions.
Keywords
