Unusual “Volcano Track” Clouds Investigated

South Sandwich Islands

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In 2008, climatic researcher Santiago Gassó authored a research study that highlighted unusually brilliant routes of clouds around remote peaks in the South Sandwich Islands. The uncommon looking clouds were triggered by volcanoes giving off sulfur dioxide and other gases and particles that connected with passing clouds and made them brighter and more long lasting than the surrounding clouds.

More than a years later on, the NASA and University of Maryland researcher is still tracking and gaining from these “volcano track” clouds over the South Atlantic Ocean. In 2020, he saw numerous of them throughout a duration of continual activity on Mount Michael. For 2 weeks in mid-May, NASA satellites observed volcano tracks almost every day.

On some days, broad tracks extended for numerous kilometers from the volcano. But on the majority of days, the tracks were thin and faint, showing that the volcanic activity was not specifically extreme. Degassing of sulfur dioxide and other gases is regular on Mount Michael, which has a consistent lava lake roiling deep inside its main crater. On May 30, 2020, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite caught this false-color picture of a volcano track near Mount Michael. Waves clouds and Von Kármán vortices show up downwind of surrounding islands.

Mount Michael

Mount Michael

Cloud lightening up—the technical term is the Twomey impact—is something researchers have actually observed for years. Clouds with additional particles from volcanoes have more and smaller sized cloud beads than regular clouds. This implies there are more surface areas to show light, making volcanically “polluted” clouds appear brighter than others. The exact same procedure produces brilliant ship track clouds over the ocean, other than because case the additional particles originate from ship exhaust.

While faint volcano tracks can be tough to see in natural-color images, near-infrared light can assist. “When I look for volcano tracks with MODIS, I use the 3-6-7 band combination because it includes near-infrared channels that are particularly sensitive to changes in droplet size, a direct result of the volcanic particles entering the cloud,” discussed Gassó. “That way the volcano track jumps out without me having to squint much.”

The lots of active volcanoes, plentiful cloud cover, regularly intense winds of the “Roaring Forties” — plus the laws of fluid characteristics—frequently produce uncommonly lovely swirls, patterns, and waves in the air above the South Sandwich islands.

The island chain has actually likewise shown to be a perfect natural lab for science. “There is a lot of interest in how human-caused pollution affects clouds on a global scale and how it is affecting the climate. But in other areas of the world, it can be difficult to tell if cloud brightening is caused by shifts in meteorology or the presence of pollution particles,” stated Gassó. “With the volcano tracks from the South Sandwich Islands, there is no question at all. The brightening is from volcanic ‘pollution,’ and that is really useful for developing models that can quantify how this cloud brightening effect works on a global scale.”

NASA Earth Observatory image by Joshua Stevens, utilizing MODIS information from NASA EOSDIS/LANCE and GIBS/Worldview.

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