济南爆发性增强冬季雾的物理特征分析

利用宏、微观观测资料，分析了济南4次出现爆发性增强冬季雾过程的类型以及形成、发展、减弱和消散的主要机制，研究了形成、发展、成熟和减弱阶段，以及爆发性增强期间的微物理演变特征，探讨了爆发性增强的触发机制。结果表明：1）夜间地面长波辐射及弱冷空气入侵造成的气温下降是济南冬季雾形成和发展的主要因素，干冷空气入侵或日出后太阳辐射加热升温，近地层相对湿度下降是雾消散或减弱的主要机制。2）形成阶段，核化和凝结增长过程启动但并不活跃，碰并强度很弱，以未碰并和偶发碰并为主；发展阶段，核化和凝结增长等微物理过程开始活跃，碰并过程启动，大滴开始增多；成熟阶段，核化、凝结和碰并增长非常活跃，各微物理量均达到最大值，谱最宽；减弱阶段，核化、凝结过程减弱，碰并过程减弱并消失，雾滴蒸发，能见度增大。3）爆发性增强的宏观物理特征主要表现为极大风速增大、气温下降、相对湿度增大、水汽压下降；微观物理特征主要表现为数浓度、液态含水量等微物理量出现跃增，以及谱型由“单峰”结构突变为“多峰”结构。4）相对湿度增大主要与气温下降有关，水汽压下降则与异常活跃的凝结增长有关；气温下降是济南冬季雾爆发性增强的直接原因，弱水汽输送产生的增湿作用对爆发性增强具有一定的促进意义。

Physical characteristics of burst reinforcement in winter fog events that occurred in Jinan

Based on the macro and micro observation data, the types and main mechanisms of formation, development, weakening, and dissipation of 4 burst reinforcement winter fog events that occurred in Jinan are analyzed, the microphysical characteristics in the stages of formation, development, mature, and weakening as well as in the course of burst reinforcement are studied, and the causes of burst reinforcement are discussed in this paper. The results are as follows. 1) The air cooling caused by the upward long-wave radiation at night and the invasion of cold air is the key to the formation and development of winter fog in Jinan, and the dissipation or weakening of winter fog owes to the decrease of relative humidity near the surface layer caused by the invasion of dry and cold air or the heating up of solar radiation after sunrise. 2) In the formation stage, the process of nucleation and condensation growth starts but is not active, the collision-coalescence process is very weak, and there are mainly no or occasional collision-coalescence process; in the development stage, the microphysical processes such as nucleation and condensation growth start to be active, the collision-coalescence process starts, and the number of big droplets increases; in the mature stage, the nucleation, condensation, and the collision-coalescence growth become very active, all the microphysical quantities reach their maximum, and the spectrum is the widest; in the weakening stage, the nucleation and condensation growth are weakened, the collision-coalescence growth becomes weak until it disappears, the droplets are evaporated, and the visibility increases. 3) The macrophysical characteristics of burst reinforcement are the increase of extreme wind speed and relative humidity and the decrease of air temperature and water vapor pressure, while the microphysical characteristics are the sharp increase of microphysical quantities such as number concentration and liquid water content and the abrupt change of spectrum distribution from one-peak to multi-peak structure. 4) The increase of relative humidity is mainly caused by the air cooling, and the decrease of water vapor pressure is mainly related to the active condensation growth; the burst reinforcement of winter fog in Jinan is directly caused by the air cooling, and the humidification caused by the weak transportation of water vapor promotes the reinforcement to some extent.