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Volcano update

24 May

The following update from our friends at Weather 2000

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“For a few weeks now we have been monitoring the sub-glacier volcanoes in Iceland, especially the one under the Grimsvötn glacier. This volcano had a powerful, explosive eruption over the weekend; melting the glacier and sending ash into the atmosphere. While things have quieted down recently, vigilance must be maintained for any sudden resurgence of volcanic activity.

Analysis has indicated that volcanic ash has been observed in the troposphere and stratosphere up to ~20 km (or ~66,000 feet). However, until the precise amount of ejecta is known, specific climate impacts are still mere speculation at this juncture. Its latitude [64°N] is far from ideal (see below) to have a significant impact on the global climate, but for the next several days solar radiation at the surface may be dimmed over the Subarctic Region in the vicinity of Iceland. The ash is heavy compared to air, and gravity settles the ash to the ground. Conversely, climate is affected by the much lighter Sulfur gases emitted from a volcano, which have a much longer residence time in the atmosphere (especially if ejected into the stratosphere).

In contrast, while Eyjafjallajökull (in 2010) sent widespread ash into Europe, due to tropospheric wind currents, this year’s weather patterns do not favor a replay of that scenario with Grimsvötn. In addition, despite ejecting ash into the stratosphere, observations indicate that the ash particles associated with Grimsvötn are much denser than those of Eyjafjallajökull, so the ash will not remain in the atmosphere as long.

In areas of greatest deposition, volcanic ash can have a significant impact on agriculture. Its effects on crops is highly dependent on the specific crop and the timing of the ash-fall. For example, the most damage to corn would occur right around the time of pollination. The effects on livestock are more obvious, with grazing animals ingesting ash particles that have settled onto pastures and water supply contamination (under more extreme conditions can lead to fluoride poisoning).

We will continue to monitor the physics & chemistry of this situation – in the case of tropical volcanoes there would be an approximate 8 to 12-month lag-time before Northern Hemispheric impacts, if any, are realized. Short-term forecasters sensationalize each Volcano that makes the news every few months, so a calm, pragmatic and scientific review of their legitimate role and limitations is appropriate:

1.) In order for Volcanoes to have weather/climate impacts beyond its region of the World, the erupted particles need to be forcefully ejected through the Tropopause and into the Stratosphere (> 12km/9 mi. for mid-Latitudes and > 16 km/11 mi. closer to the Equator), where they can diffuse and eventually have a global reach.

2.) Separately, keep in mind that any Volcanoes located Poleward of 30° have only small impacts on Hemispheric climate. Unlike Pinatubo and Tungurahua (both located in the Tropics), Volcanoes closer to the Poles will have their contents advected toward the Northeast/Poles.

3.) Regionally, larger soot and erupted particles (> 2.2 µm) are more effective at keeping in Infrared radiation and can impart some warming effects. Smaller particles (usually containing lots of sulfur) are less effective in the IR spectrum, but stay aloft longer and increase Albedo and hence lead to cooling. (FYI, Volcanic Ash is not actually ash, but tiny jagged particles of rock and natural glass). After the infamous 1980 Mount Saint Helens eruption it took several weeks to cart away all the Ash & Soot, and until that is done in any future events, could be blown around obscuring visibility in much the same way a Forest Fire would.

4.) At the lower levels of the Troposphere, Soot & Ash (if fine enough) could also act as condensation nuclei and perhaps help “feed” regional storm systems during an upcoming Season. Ionization of the atmosphere is a tertiary impact of this particulate matter that could translate into increased lightning events also during the upcoming Season. Such particles were detected as far away as New England following the 1980 Mount St. Helens eruption.

Courtesy of the

Climate Research & Forecasting Teams

Weather 2000, Inc. New York

Tel. +1 212 465 2121

http://www.weather2000.com

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