Vog

(A current animated version can be viewed -Here-)

What is Vog?  The University of Hawaii's School of Ocean and Earth Science and Technology (UH SOEST) defines it as follows:

Vog is primarily a mixture of sulfur dioxide (SO2) gas and sulfate (SO4) aerosol. SO2 (invisible) reacts with oxygen and moisture in the air to produce SO4 aerosol (visible). SO2 is expected to be the main problem in areas near the vent (Hawai`i Volcanoes National Park, Pahala, Na`alehu, Hawaiian Ocean View Estates) and SO4 aerosol is expected to be the main problem at locations far from the vent (Kona and farther north and west).

In LA or NYC they'd call it Smog.  The sources may be slightly different, but the effects on people and plant life are largely the same.  In Hawaii it's a natural process and results from eruptive activity at the Kilauea Volcano.  As the graphic above shows, the areas most affected by the vog here are those immediately west of the eruptions themselves that lie on the path of normal trade wind patterns.

Over the years I've posted a number of photos showing what the sky looks like at sunset when vog is particularly evident... but until you see where it comes from and where it goes it's kind of hard to grasp what the effect is here.  The SOEST graphic above is updated frequently and is part of an ongoing Vog Measurement and Prediction Project.  It shows output in graphical form from the HYSPLIT dispersion model.  Those who live here really don't need a reminder.  We've seen it just about every day since Halemaumau blew up in April 2008.

"vog" sunset taken above Puako Mar 7, 2008