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一次飞机积冰过程的气象条件和微物理特征分析

Analysis of Meteorological Conditions and Microphysical Characteristics of an Aircraft Icing Event

  • 摘要: 飞机积冰严重威胁飞行安全,为更好地了解飞机积冰的气象条件和云微物理特征,寻找积冰与宏观气象条件阈值之间的关系,本文利用飞机观测资料,结合雷达、欧洲中期天气预报中心ERA5再分析资料,对2018年12月10日河南中东部冬季一次飞机严重积冰过程的天气条件和云微物理过程进行了分析,并对此次积冰强度进行了评估。此次积冰过程是受高空槽、低层切变以及地面冷高压的共同作用,流向河南的低层暖湿空气沿着冷高压爬升,形成上暖下冷的逆温层,促进了该区域内液态水的积聚。积冰区域内液态水含量丰富,而冰水含量较低,液态水含量主要分布在550~750hPa高度之间。飞机观测数据与ERA5再分析资料结果较为一致,强积冰区在3630m高度层上,云中温度为-8.21~-6.79℃,相对湿度在87%~92%,平均云滴数浓度为499.96cm-3,液态水含量最大可达0.87g/m3,该区域内大小过冷液滴共存,基本无冰晶粒子。通过计算:飞机穿过液态水含量丰富区发生轻度积冰、中度积冰、严重积冰时的液态水含量阈值分别为0.05g/m3、0.20g/m3、0.58g/m3。当逆温层强度为1.93℃/100hPa、垂直运动速度在-0.25~0.2Pa/s、水平辐合强度为-3.73kg/(m**2*s)的情况下,积冰强度达到中度以上的概率为77%。

     

    Abstract: Aircraft icing poses a serious threat to flight safety. To better understand the meteorological conditions and cloud microphysical characteristics of aircraft icing, and to find the relationship between icing and the threshold of macro meteorological conditions, this study used aircraft observation data, combined with radar and ERA5 reanalysis data from the European Centre for Medium-Range Weather Forecasts, to analyze the weather conditions and cloud microphysical processes of a severe aircraft icing event in central and eastern Henan Province on December 10, 2018. The intensity of the icing event was also assessed. This icing event was caused by the combined effects of an upper-level trough, low-level shear, and surface cold high pressure. Warm and moist air at low levels flowing towards Henan ascended along the cold high pressure, forming an inversion layer with warm air above and cold air below, which facilitated the accumulation of liquid water in the region. The icing area was rich in liquid water content but had low ice water content, liquid water content is significantly higher between the altitudes of 550 to 750hPa compared to other altitudes. The aircraft observation data is relatively consistent with the results of ERA5 reanalysis data, the severe icing area was at an altitude of 3630m, with cloud temperatures between -8.2 and -6.8°C, relative humidity between 87% and 92%, an average cloud droplet concentration of 499.9cm-3, and a maximum liquid water content of up to 0.87g/m3. In this area, large and small supercooled liquid droplets coexisted, with virtually no ice crystal particles. Calculations showed that the thresholds for light, moderate, and severe aircraft icing in areas rich in liquid water content were 0.05g/m3, 0.20g/m3, and 0.58g/m3, respectively. Under conditions where the inversion layer strength was 1.93°C/100hPa, vertical motion speed ranged from -0.25 to 0.2Pa/s, and horizontal convergence intensity was -3.73kg/(m2s), the probability of icing intensity reaching moderate or above was 77%.

     

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