How specifically do volcanos change weather patterns?

rocky Les Thomas

Dear Les,

Volcanoes can easily affect local weather patterns during explosive eruptions. The huge amounts of ash and water vapor that are pumped into the atmosphere have dramatic affects, from causing fierce lightning storms to torrential rains to rains of mud. These effects are usually easy to explain from the actions of ash particles as nucleii for raindrops forming, the fact that much of the gas erupted by volcanoes is water to begin with, greatly increased upward air currents in the vicinity of an erupting column, etc.

What are harder to explain are the affects of volcanoes on the large-scale climate and weather globally. For one thing, we know that small ash and aerosol particles are able to reflect incoming solar radiation and this causes global cooling. Pinatubo, for example, caused a worldwide cooling of about 1/2 degree C. Such changes in temperature have effects on some of the large-scale high and low-pressure zones around the world, and these are what directly affect weather. One relationship has to do with the big high and low-pressure cells that develop over places such as central Asia, the N. Pacific, S. America, etc. In hot areas (such as large continental areas), air rises, producing zones of low pressure. In cooler areas (such as over large oceanic areas, downward-moving air causes high pressure. All of our winds are due to air moving from low pressure areas to high pressure areas, and things such as rainfall, wave action, and air moisture at any one place are due to the winds. If you go and change things, such as by cooling the earth, the continents will react first--the continents will be cooler and thus the low pressure zones won't form, and the pattern of global winds will be very different. Consequences at any one location can be great or not noticeable, depending on many factors.

It is quite a complicated picture, but hopefully I've been able to at least give you an appreciation to what some of the variables are.

Scott Rowland, University of Hawaii 

Other Categories        Other Questions

To VolcanoWorld