南方典型山区宏微观因子对高时间分辨率积冰属性影响及冰层脱落机理的观测研究

The wire icing will be harmful to the normal operation of the transmission lines, especially those erected in mountainous area which are suffered serious damage caused by the combined effect of three types icing. Ice breakage and shedding will lead to unbalanced power line tension resulting in a series of secondary disasters such as line galloping, disconnection, flashover, damaged fittings and collapsed towers frequently. The external performance of ice process is the variation of ice thickness, ice weight, and ice density, while the physical reason is the variation of meteorological elements and macro-microphysical properties of freezing fog/rain. Unfortunately, the variations of high-time-resolution icing properties and the characteristics of macro-micro influence factors are barely observed and researched, and the recognitions on ice shedding mechanism are even less. A comprehensive field observation project on wire icing will be conducted in mountainous areas of Enshi and Shenongjia, observing the icing properties every 10s and other elements by anti-icing observation instruments. The characteristics of icing properties are revealed during the formation, growth, maintenance, and shedding periods of three icing types. The response of icing properties to the variations of influence factors are investigated. The relationship model of icing features and microphysical characteristics of freezing fog/rain will be established according to different stages and layers. The effects of icing properties, meteorological elements and radiation characteristics on ice shedding processes are studied, and obtaining the shedding model which will reflect the shedding type, shedding time and shedding intensity quantitatively. The achievements will improve the understanding of the whole process of wire icing in mid-high altitude mountainous areas, and provide the scientific basis for the warning and prevention to the icing disaster of transmission lines.

架设在山区的输电线路受多种类型积冰共同作用下的复合型积冰过程影响严重，并且积冰脱落导致输电线路张力不平衡所引起的舞动等次生灾害也日益频发。积冰过程的外在表征是冰厚、冰重和冰密度等属性的改变，而物理成因则是气象要素和过冷云雾降水等宏微观因子的变化，但目前将两者有机结合的研究较少。本项目拟在湖北省恩施和神农架山区以10s间隔的多种积冰属性观测为核心，结合地面抗冰观测仪器所得的气象要素、辐射通量和过冷云雾降水宏微观特征等因子的资料，揭示不同类型积冰过程中发生、发展、维持和脱落阶段积冰属性的变化特征，探讨积冰属性对宏微观影响因子演变的响应，构建分阶段、分层次的积冰属性与云雾降水微物理特征的关系模型，给出积冰属性、气象条件和辐射特征对积冰脱落过程的影响，建立定量反映积冰脱落方式、脱落时间和脱落强度的多影响因子模型，完善对中高海拔山区积冰全过程物理机制的认识，为输电线路积冰灾害预警和防治提供理论依据。

收集和整理了2008—2016 年冬季湖北恩施雷达站、金沙本底站、神农架大草坪和神农顶观测得到的40余次持续时间超过24小时的完整电线积冰过程观测资料。对我国西南山区降水宏微观过程的多尺度变化特征进行了统计研究，西南山区与平原地区最大的区别是其降水滴谱峰值要比平原地区高约1-2个数量级，并发现山上较大的风速导致大雨滴破碎使得山顶小粒子的数密度要大于山下，而山下高蒸发率、较强的CAPE。研究了我国中部江汉平原地区区域冻雨过程微物理参数演变特征及其形成机制，区域冻雨事件的增强主要以雨滴数浓度增加为主，受雨滴直径影响较弱，随着降水的持续，霰或雪花的出现显著降低了降水过程中冻雨的占比，江汉平原区域冻雨的形成过程，以微淞附的霰和大而干的雪花融化为主，受到暖雨过程、凝华、聚并/淞附等物理机制以及某些时期弱对流运动的共同影响。山区积冰的持续时间是影响其过程最大冰厚的关键因素，雨凇过程中冻毛毛雨的发生时次最集中，且其出现可能导致冰厚爆发性增长，有无冻毛毛雨出现时段的冰厚增长率平均值分别为1.26 mm·h-1和-0.11 mm·h-1，碰撞率是抑制过冷雾积冰的主要参量，而冻结率则是抑制冻毛毛雨积冰的主要参量。分析和比较了三种天气（冻雨、雪和过冷雾）下结冰的增长和脱落机制。考虑到混合产冰条件，通过结合冰冻雨、雪和过冷雾结冰模型，结合降水率和风速等输入，模拟了冰层厚度，在雪和过冷雾中，结冰增长率与温度和风速之间的相关性强于冻雨，随着气温的降低，结冰增长率随雪的增加而加快，而过冷雾中的结冰增长率随着风速的增加而增加，构建的综合物理模型可以很好地模拟实际冰厚的变化。