Haze is a mixture of fog and haze and they are two different kinds of weathers. Different from the fog, haze is a kind of di⁃sastrous weather. From the phase change of material and the distribution of mass, the formation mechanism of haze will be analyzed. Fog is a phase transformation process from water gas phase to liquid phase or solid phase. Temperature is the main factor that influences the phase transformation from gas to liquid (or gas to solid). The main reason of the occurrence of haze is the existence of higher density of aerosol particles in the air. Theoretical analysis shows that the elevation of aerosol particles in lower temperature season is less than the higher temperature season, the density of the aerosol particles is inversely proportional to the elevation, and the theoretical results are consistent with the monitoring results. The large number of aerosol particle generated by human activities is the internal cause of haze for⁃mation, natural weather condition is the external cause of haze formation. Reduce the aerosol particles emissions is the key to control haze occur. Although environmental protection is a problem relating to many aspects and a complex one, we can start from the simple and easy ways, take measures step by step to control the haze from an appealing into practical action.%雾霾是雾和灰霾的混合体，它们是两种不同的气象。有别于雾，灰霾是一种灾害性气象。从物质的相变与质量的分布规律，分析雾霾的形成机制。雾是由水的气相转变为水的液相或固相的相变过程。对于雾来说，温度是影响气液（气固）相变的主要因素。灰霾发生的主要原因是空气中存在较大密度的气溶胶微粒。理论分析表明，温度较低的季节，气溶胶微粒的标高小于温度较高季节的标高，气溶胶微粒密度与标高成反比，理论结果与实际监测结果一致。人类活动产生大量气溶胶颗粒是灰霾现象形成的内因，自然气象条件是灰霾形成的外因。减少气溶胶颗粒物的排放，是控制灰霾天气发生的关键。尽管环境保护是一个涉及多方面且错综复杂的问题，但是我们可以从简单易行的工作做起，分步骤地采取措施，从呼吁倡导层面转变为实际行动，对灰霾予以控制。
展开▼
