III. Weather Phenomena

1. Haze

In meteorology, haze is caused by suspended dry solid particles in the air such as dust or salt. Due to the extreme smallness of these particles they are invisible to the naked eye. Haze is usually milky white in the atmosphere, while against a bright background it will become yellow or orange-red; likewise, against a darker background it will be light blue. This is due to optical effect caused by the haze particles; i.e. the scattering of light by the haze particles. Haze is an atmospheric phenomenon in meteorological observation, and is formally called lithometeors. It can obscure vision and directly influence horizontal visibility. Currently the World Meteorological Organization has not established a classification of haze densities.

Smoke is caused from suspended solid particles formed by the combustion of objects. In meteorological observation it is also a type of dust phenomenon. Smoke can also directly influence horizontal visibility and creates obscured vision. Sometimes smoke has a yellow-green hue due to the sunlight scatters. When smoke and fog combine into smog, then it will be grey or yellow.

During September and October 1997, there was a forest fire in Indonesia, which created a huge amount of dense smoke. The dense smoke was diffused through air currents, which forced nearby countries in Southeast Asia such as Malaysia, to shutdown their airports due to low visibility. This created severe transportation damage to the region while at the same time creating serious air pollution. The large amount of suspended smoke and dust and other harmful particles endangered human health. Many activities were forced to be suspended. This kind of direct or indirect damage caused by smoke or haze is called "haze pollution".