Volcanic activity « CIMSS Satellite Blog

Another significant volcanic ash plume from Eyjafjallajökull in Iceland

May 6th, 2010

Meteosat-9 SEVIRI volcanic ash retreival products

Meteosat-9 SEVIRI volcanic ash retrieval products

The Icelandic volcano Eyjafjallajökull (which started to become active again in late March 2010) continued to remain active into early May, with another significant plume being observed on 06 May 2010. EUMETSAT Meteosat-9 SEVIRI volcanic ash retrieval products (above) showed a plume streaming southeastward from Iceland, with the maximum ash cloud height reaching 17.27 km. These volcanic ash retrieval products provide a demonstration of the type of products that will be available with the ABI instrument on the GOES-R satellite — they are available in near-realtime on the CIMSS GOES-R Proving Ground site.

A Terra MODIS Red/Green/Blue (RGB) image (using bands 01/04/03) shows the brown ash plume curving southeastward and then southward over the eastern Atlantic Ocean (below).

Terra MODIS RGB image (using bands 01/04/03)

As a result of this most recent volcanic eruption, some airports in Scotland, Northern Ireland and the Irish Republic were closed on 06 May.

===== 07 MAY UPDATE =====

A Terra MODIS RGB image using bands 01/04/03 (below) showed a very long and narrow volcanic plume emanating from Eyjafjallajökull on 07 May.

Terra MODIS RGB image (using bands 01/04/03)

Posted in GOES-R, Meteosat, MODIS, Red/Green/Blue (RGB) images, Volcanic activity | No Comments »

Eyjafjallajökull volcanic eruption continues

April 19th, 2010

Aqua MODIS Red/Green/Blue (RGB) image

The eruption of the Eyjafjallajökull volcano on southern Iceland continued on 19 April 2010 (in addition, see the previous CIMSS Satellite Blog entries published on 15 April and 21 March). A McIDAS Red/Green/Blue (RGB) image composite using Aqua MODIS channels 01/04/03 (above) revealed yet another large ash plume streaming southward over the North Atlantic Ocean. According to the London Volcanic Ash Advisory Center (VAAC), the ash from this latest eruption was generally confined to 10,000-15,000 feet and lower. With the volcanic ash plume drifting to the south, air traffic in the immediate vicinity of Reykjavik-Keflavik International Airport (station identifier BIKF) was not affected — and after a 5-day shut-down of air traffic across much of Europe, some airports there were finally beginning to allow limited flights to resume.

The corresponding volcanic ash retrieval products (below, courtesy of Mike Pavolonis, NOAA/NESDIS/STAR/CoRP/ASPB) indicated that the total ash loading was 75.82 kilotons, the maximum ash height was 7.37 km, and the mean ash particle effective radius was 3.51 micrometers. Note that these volcanic ash retrieval products are available in near-realtime at this NOAA/NESDIS/STAR/CIMSS site.

MODIS volcanic ash retrieval products

In addition to MODIS instruments on Terra and Aqua, the AVHRR instrument on the NOAA polar orbiters can give information on the state of the eruption. NOAA-19 passed over Iceland at 04:08 UTC 19 April, and NOAA-16 passed over at 09:16 UTC 19 April. What do the two views suggest?

Only the NOAA-16 pass occurred during daylight, and that image, below, centered on the Volcano, shows a plume extending southward from Iceland in the wake of a low pressure system (the cyclonic swirl of clouds in the eastern half of the image) departing to the east.

Infrared imagery from 0408 UTC and 0916 UTC today suggest how the ash cloud may be changing with time. The 3.74 micron imagery and the 10.8-micron imagery, below, both show an increase in the area covered by the plume. This suggests an ongoing eruption. The 10.8-micron imagery in particular shows a lengthening of the volcanic plume southward from Iceland. The 3.74 micron imagery is affected by radiation reflected from the Sun. The 0408 UTC image occurred before sunrise. Only radiation emitted by the Earth, or clouds, or ash, is detected by the satellite. Note the warm (dark) spot that colocates with the volcano: brightness temperatures there are 20 K warmer than surrounding pixels. The 0916 UTC occurred during daylight, and as such, solar radiation at 3.74 microns can be reflected off the Earth and detected by the satellite. The sum total of radiation (emitted plus reflected) will always be greater than only the emitted radiation, thus the scene will appear warmer (and in the greyscale enhancement, darker): the “extra” radiation detected by the satellite is interpreted to mean a warmer emitting surface. Note the striking appearance of the plume. It is very dark (warm) because the particles in the plume are highly reflective. At 0916 UTC, the volcano still retains its dark spot presence in the 3.74 micron imagery. The brightness temperature remains about 20 K warmer than at surrounding pixels.

===== 20 APRIL UPDATE =====

MODIS Red/Green/Blue (RGB) and 3.7 µm shortwave IR images

Eyjafjallajökull continued to erupt on 20 April 2010. An Aqua MODIS Red/Green/Blue (RGB) image (above) showed a thin but well-defined cloud plume (likely a plume of volcanic steam) arcing southeastward, with a hint of a broader volcanic ash plume spreading out southward from the volcano. The corresponding MODIS 3.7 µm shortwave IR image displayed a pronounced “hot spot” (yellow to red color enhancement) associated with the source of the eruption.

An animation of Meteosat-9 volcanic ash retrieval products (below) indicated that the cloud heights decreased rapidly with time (likely a result of relatively large particles), and the ash cloud quickly became undetectable with increasing distance from the source volcano, due to its low optical depth and obstruction by meteorological clouds.

Meteosat-9 volcanic ash retrieval products

Posted in AVHRR, Aviation, MODIS, POES, Red/Green/Blue (RGB) images, Volcanic activity | No Comments »

Volcanic Ash over the North Atlantic

April 15th, 2010

Eyjafjallajökull, a now-active volcano in southern Iceland that erupted in late March, has recently erupted again, ejecting significant volcanic ash into the atmosphere. Iceland is at high enough latitudes (between 63 and 66.5 degrees north Latitude) that views from geostationary satellites are not as helpful in diagnosing evolving events such as ash clouds as they would be for lower-latitude events. Meteorologists instead rely on polar orbiters to observe the atmosphere surrounding the eruption.

For example, A Terra overpass yesterday allowed MODIS to image the eruption, shown as a true color composite below.

Ash from volcanoes is a significant aviation hazard if it is drawn into jet turbines. For that reason, all flights at London’s Heathrow (and at other airports throughout northern Europe) have been grounded as of mid-afternoon London time on 15 April. The volcanic ash cloud is visible from satellite. The imagery above shows 10.8- and 12.0-micron imagery from a NOAA-18 pass at 0342 UTC on 15 April. The volcanic plume is visible as colder cloud tops arcing eastward from Iceland towards northern Scotland. The color enhancement in the loop shows that the 12.0-micron image has colder brightness temperatures than the 10.8-micron image. For example, the coldest point (red pixels) just off the coast of Iceland have 12.0-micron brightness temperatures of 212.6 K; 10.8-micron temperatures in that region are closer to 214.5 K. This difference in temperature arises because volcanic ash has a lower emissivity at 12.0 microns than at 10.8 microns. Thus, proportionally less radiation compared to a blackbody is being emitted at 12.0 microns than at 10.8 microns. When that emitted radiation is detected by the satellite, the proportionally smaller values at 12.0 microns yield cooler blackbody temperatures.

Indeed, a difference between the two channels can yield a rough approximation of the ash cloud outline, and that is shown above. Colored pixels here have 10.8-micron brightness temperatures at least 2 K warmer than the 12.0-micron brightness temperature. Maximum temperature differences exceed 10 K.

Meteosat-9 volcanic ash products (15 April)

15-16 April Update: The SEVIRI instrument on Meteosat-9, with more spectral resolution than AVHRR, can yield more information about the ash cloud, including total mass, maximum height, and effective radius. These derived products (courtesy of Mike Pavolonis, NOAA/NESDIS/STAR/CoRP/ASPB) are shown for 15 April (above; also available as a QuickTime movie), and for 16 April (below; also available as a QuickTime movie).

Meteosat-9 volcanic ash products (16 April)

18 April Update: below are individual quantitative volcanic ash product images that show characteristics of the volcanic ash features at various times and locations during the 16-18 April period.

Meteosat-9 volcanic ash products at 06:00 UTC on 16 April

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Meteosat-9 volcanic ash products at 18:30 UTC on 16 April

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MODIS volcanic ash products at 03:40 UTC on 17 April

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MODIS volcanic ash products at 04:20 UTC on 18 April

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MODIS volcanic ash products at 12:05 UTC on 18 April

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MODIS volcanic ash products at 14:00 UTC on 18 April

A McIDAS image of a 500-meter resolution Aqua MODIS Red/Green/Blue (RGB) composite using channels 01/04/03 (below) shows a beautiful view of the volcanic ash plume streaming southward on 17 April 2010. Annotated on the image are the tiny village of Skógar, as well as the Mýrdalsjökull Glacier. As an aside, it is interesting to note that a great deal of lightning has been observed associated with the volcanic ash cloud.