How are the volcanoes in Hawaii affecting the current weather? Have they affected the weather at any time in history?
Tracy Masters
Hi Tracy,
There is some disagreement about whether the eruption is affecting the
weather or not. The erupting vent is on the windward side of the island
where it rains a lot. The eruption doesn't seem to have had an affect on
the weather in this area. However, on the leeward side of the island,
there may be some affects. The trade winds tend to blow the sulfur
dioxide plume down around the southern part of the island and then
stagnate on the leeward side. Over the past 13 years or so of the
eruption the air quality over there has gotten pretty bad and supposedly
it is on par with Pittsburg. Coinciding with all this has been a
noticeable drop in rainfall on that part of the island.
The rainfall over there isn't that high to begin with because it is in the
lee of Mauna Loa and Mauna Kea. What rain there is comes from land-sea
breezes: During the day the land heats up more than the ocean and air
rises over the land. This draws moist air in off the ocean which then
rises, cools, and causes rain. The famous Kona Coffee industry relies on
this almost daily rain. The volcano produces sulfur dioxide which reacts
with water in the atmosphere to produce sulfuric acid aerosols (tiny
droplets). The story I heard is that you need small particles or droplets
for rain drops to nucleate on, but they work best if they are a variety of
sizes. The problem with the sulfuric acid aerosols is that they are
pretty much all the same size and therefore don't help to nucleate
raindrops. I guess since there are now so many of them they dominate the
particle population and hinder the formation of the drops.
I don't think this theory has yet been proven 100% (if at all).
Sincerely,
Scott Rowland, University of Hawaii