Vog Levels Now Measurable and Predictable

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Until recently, vog has been difficult for scientists to measure and predict.

Last February, however, meteorologists at the University of Hawaii developed a system for predicting the concentration and dispersion of sulfur dioxide that spews from Kilauea Volcano.

Spectrometer arrays have been installed at the volcano as part of the Vog Measurement and Prediction Project. Sulphuric acid absorbs light, and spectrometers measure light from the sky, thus enabling scientists to gather input which is translated into a usable vog index.

“Basically, the spectrometers measure how much gas is being emitted by the volcano,” said Steven Businger, senior professor at the University of Hawaii Department of Meteorology on Oahu.

Businger has been studying the vog since the early 1990s. He and his colleagues, including lead modeler Roy Huff, have now created a series of web pages designed to provide forecasts and safety guidelines, and to raise public awareness around the hazards of volcanic emissions. Color coded maps of the island indicate daily ratings from good, moderate, unhealthy, very unhealthy and hazardous.

Varying degrees of vog pose health threats to island residents and visitors. The primary irritants in vog are sulfur dioxide and tiny sulfuric acid droplets called aerosols. Those who are sensitive may experience anything from mild irritation to headaches, watery eyes and a sore throat, to breathing difficulties, including inducing asthma attacks, flu-like symptoms, and general lethargy.

Emissions from Kilauea Volcano have been producing flumes and clouds over the Big Island since it began erupting again in 1983. These clouds are carried by the wind and disperssed across the islands as an unpleasant cloud of volcanic smog, or what we commonly refer to as “vog.”


Because Hilo is so much closer to the erupting vents, there is less time for the vog to disperse and react with the atmosphere. As one would expect, the air nearer the volcano contains higher concentrations of sulfur dioxide and sulfuric acid aerosols than are found on the other side of the island, and the air is correspondingly more unpleasant. In extreme cases, visibility in East Hawaii can be less than a couple of miles. When winds are light and variable, the vog accumulates in areas closest to the emitting vents, and communities such as Mountain View and Glenwood, which are near Pu’u O’o vent, see high concentrations of vog. When the wind blows from the south, Kona enjoys clean air, but Hilo suffers. When Kona winds blow north, they bring vog to other islands.

For current vog conditions go to

and click on the current vog aerosol conditions map. For current vog and health related information, has information from a number of cooperating State and County agencies such as the Department of Health and the County Civil Defense.




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