基于IC指数的中国飞机积冰时空变化特征及其与大气环流的关系

Spatial and Temporal Variation Characteristics of Chinese Aircraft Icing Based on IC Index and Its Relationship with the Atmospheric Circulation

摘要: 本文利用最新一代大气再分析资料(ERA5)，基于IC指数研究了我国东部飞机积冰时空变化特征，并进一步通过合成分析解释了其与大气环流场的内在关系。结果表明：冬季我国飞机积冰在700 hPa高度层比较显著，空间分布呈现出较强的地域差异，强度主要表现为轻度积冰，中度以上积冰集中分布在川渝交界区域，积冰日数最多的地方出现在长江流域。对逐月积冰概率进行EOF分解的结果表明，第一模态以31˚N为界呈南北偶极型分布，呈现出准4年和准13年的年际及年代际变化。第二模态则反映了我国中东部积冰概率的一致偏小或偏大，并且具有显著的3.5年和6年左右的年际变化特征。不同模态对应的大气环流形势存在明显差异。积冰概率呈南北偶极型时，我国上空存在的气旋式或反气旋环流，通过影响水汽输送过程影响南北两侧的水汽条件，从而改变积冰概率。当积冰概率表现为一致变化型时，我国东北以东和西北以西的上空存在相反的环流形势，通过在它们之间的过渡区形成一致的偏南(或偏北)气流将暖湿(或干冷)空气输送入我国中部区域，从而改变其积冰概率。

Abstract: In this paper, the latest generation of atmospheric reanalysis data (ERA5) is used to study the temporal and spatial variation characteristics of aircraft icing in eastern China based on IC index, and its intrinsic relationship with the atmospheric circulation field is further explained through synthetic analysis. The results show that aircraft icing in China in winter is more significant at the altitude layer of 700 hPa, and the spatial distribution shows strong regional differences, the intensity is mainly manifested as mild ice accumulation, moderate aircraft icing is concentrated in the Si-chuan-Chongqing junction area, and the place with the largest number of aircraft icing days appears in the Yangtze River Basin. The results of EOF decomposition of the monthly aircraft icing probability show that the first mode is distributed in a north-south dipole type bounded by 31˚N, showing interannual and decadal changes in quasi-4 years and quasi-13 years. The second mode reflects the small or large consistency of ice accumulation probability in central and eastern China, and has significant interannual variation characteristics of about 3.5 years and 6 years. There are obvious dif-ferences in the atmospheric circulation situation corresponding to different modes. When the ice probability is a north-south dipole type, the cyclonic or anticyclonic circulation existing over China affects the water vapor conditions on the north and south sides by affecting the water vapor transport process, thereby changing the probability of ice accumulation. When the ice probability is manifested as a uniform variation, there is an opposite circulation situation in the sky east of northeast and west of northwest China, and warm and humid (or dry cold) air is transported into the central region of China by forming a consistent southerly (or northerly) air flow in the transition zone between them, thereby changing its ice accumulation probability.