台风外围静小风加深的成因机制

The Analysis of Cause Mechanism of Weak Winds Deepening in the Peripheral Subsidence Region of Typhoon

摘要: 台风是引起珠三角地区高臭氧污染发生的典型天气系统。台风发生时其外围下沉区气象要素会发生显著变化。比如，高温、低湿、高辐射以及近地面出现静小风等。气象要素的显著变化是高浓度臭氧发生的主要原因而非排放源的突然增加。很多研究表明：边界层内静小风不利于臭氧污染的扩散，是臭氧污染发生的一个重要气象因素。并且，相关研究指出，台风发生时其外围下沉区不仅会出现静小风而且会出现静小风厚度加深。静小风厚度加深不利于边界层上层臭氧污染的扩散，在垂直混合作用下，上层臭氧污染会被带到地面，从而引起地面高臭氧污染的发生。热成分理论可以一定成都上解释静小风厚度加深的成因机制。

Abstract: Typhoons are a typical weather system that triggers high ozone pollution in the Pearl River Delta region. When a typhoon occurs, significant changes take place in meteorological factors within its peripheral subsidence zone, such as high temperatures, low humidity, intense solar radiation, and calm or light winds near the surface. These pronounced changes in meteorological conditions, rather than a sudden increase in emission sources, are the primary cause of high-concentration ozone events. Numerous studies have shown that calm or light winds within the boundary layer hinder the dispersion of ozone pollution, serving as a key meteorological factor in ozone pollution episodes. Furthermore, relevant research indicates that during typhoon events, not only do calm or light winds occur in the peripheral subsidence zone, but the depth of the calm-wind layer also increases. The thickening of this calm-wind layer impedes the diffusion of ozone pollution in the upper boundary layer. Through vertical mixing, ozone pollution from the upper layers is transported to the surface, leading to the occurrence of high ground-level ozone pollution. The thermal component theory can, to some extent, explain the formation mechanism behind the deepening of the calm-wind layer.