A whirlpool 'Warhol' from NASA's Spitzer telescope

Unlike Andy Warhol's famous silkscreen grids of repeating images rendered in different colors, the varying hues of this galaxy represent how its appearance changes in different wavelengths of light—from visible light to ...

Extratropical volcanoes influence climate more than assumed

The eruption of Mount Pinatubo in 1991 had a significant impact on climate, decreasing global mean temperature by about 0.5°C. Like the famous eruptions of Krakatau (1883) and Tambora (1815), Pinatubo is located in the tropics, ...

Haze smoke affects butterfly caterpillars

NUS biologists have discovered that haze affects the survival and development of butterflies, which could have an adverse impact on our environment.

Hard to see, hard to breathe: US West struggles with smoke

Smoke from wildfires clogged the sky across the U.S. West, blotting out mountains and city skylines from Oregon to Colorado, delaying flights and forcing authorities to tell even healthy adults in the Seattle area to stay ...

Pluto's hydrocarbon haze keeps dwarf planet colder than expected

The gas composition of a planet's atmosphere generally determines how much heat gets trapped in the atmosphere. For the dwarf planet Pluto, however, the predicted temperature based on the composition of its atmosphere was ...

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Haze

Haze is traditionally an atmospheric phenomenon where dust, smoke and other dry particles obscure the clarity of the sky. The World Meteorological Organization manual of codes includes a classification of horizontal obscuration into categories of fog, ice fog, steam fog, mist, haze, smoke, volcanic ash, dust, sand and snow. Sources for haze particles include farming (ploughing in dry weather), traffic, industry, and wildfires.

Seen from afar (e.g. approaching airplane) and depending upon the direction of view with respect to the sun, haze may appear brownish or bluish, while mist tends to be bluish-grey. Whereas haze often is thought of as a phenomenon of dry air, mist formation is a phenomenon of humid air. However, haze particles may act as condensation nuclei for the subsequent formation of mist droplets; such forms of haze are known as "wet haze."

In the United States and elsewhere, the term "haze" in meteorological literature generally is used to denote visibility-reducing aerosols of the wet type. Such aerosols commonly arise from complex chemical reactions that occur as sulfur dioxide gases emitted during combustion are converted into small droplets of sulfuric acid. The reactions are enhanced in the presence of sunlight, high relative humidity, and stagnant air flow. A small component of wet haze aerosols appear to be derived from compounds released by trees, such as terpenes. For all these reasons, wet haze tends to be primarily a warm-season phenomenon. Large areas of haze covering many thousands of kilometers may be produced under favorable conditions each summer.

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