Eruption of the Kelut volcano in Java, Indonesia

February 13th, 2014
MTSAT-1R 10.8 µm IR channel images (click to play animation)

MTSAT-1R 10.8 µm IR channel images (click to play animation)

McIDAS-X images of MTSAT-1R 10.8 µm IR channel data (above; click image to play animation; also available as an MP4 animation) showed the rapid expansion of the volcanic umbrella cloud resulting from the eruption of Kelut (aka Kelud) on the Indonesian island of Java on 13 February 2014. The MTSAT-1R satellite was in rapid scan mode, providing images at 10-minute intervals (with some gaps). The initial signal of a volcanic cloud appeared as a small cluster of cold pixels on the 16:09 UTC (11:09 PM local time) IR image.

The dramatic signature of a distinct circular-shaped warm core (shades of red, around -60º C) surrounded by a ring of colder (shades of white, -75º to -80º C) cloud-top IR brightness temperatures possibly indicated that a portion of the cloud plume associated with the explosive eruption rose well into the lower stratosphere, and was therefore radiating at the warmer temperatures that existed far above the tropopause. The leading edge of the top of the cloud plume eventually exhibited IR brightness temperatures colder than -80º C (shades of violet) as it drifted toward the west-southwest, with a minimum of -84.5º C on the 19:29 UTC image. Along the upwind (eastern) portion of the volcanic cloud, a signature of “bow shock waves” was evident: an indication that the massive and dense volcanic cloud was acting as a barrier to the ambient easterly flow across the region. Volcanic lightning was also generated by the rising ash plume (see photos on the Wired Science “Eruptions” blog posts 1 and 2).

Suomi NPP VIIRS 11.45 µm IR channel and 0.7 µm Day/Night Band images

Suomi NPP VIIRS 11.45 µm IR channel and 0.7 µm Day/Night Band images

A more detailed view was provided by McIDAS-V images of Suomi NPP VIIRS 375-meter resolution 11.45 µm IR channel and 750-meter resolution 0.7 µm Day/Night Band data (above; images courtesy of William Straka, CIMSS). A ring of gravity waves could be seen around the periphery of the volcanic cloud shield; the coldest IR brightness temperature within the small cluster of “overshooting tops” was 175 K or -98º C (closer view). Since the Moon was in the Waxing Gibbous phase at 98% of full, it provided ample illumination for a “visible image at night” using the VIIRS Day/Night Band — note how the ash-laden volcanic cloud exhibited a darker gray appearance compared to the surrounding brighter white meteorological clouds.

Surabaya/Juanda rawinsonde data (12 UTC on 13 February)

Surabaya/Juanda rawinsonde data (12 UTC on 13 February)

A plot of the 13 February/12:00 UTC rawinsonde data from the nearby (map/IR image comparison) Surabaya/Juanda International Airport (above) showed that a very moist and marginally unstable (Lifted Index of only  -1.7) atmosphere existed over the region about 4 hours prior to the eruption — the tropopause was located at 105 millibars (mb), at an altitude of 16.29 km where the air temperature was -84.5º C. According to the volcanic ash advisory issued by the Darwin VAAC at 00:43 UTC on 14 February, the top of the volcanic ash extended to 55,000 feet or 16.76 km — somewhere between 100 mb and 87.1 mb on the Surabaya sounding. The warmest temperature recorded in the stratosphere by the sonde instrument was -71.3º C at 64.9 mb or 19.02 km.

A GOES-R Volcanic Ash Height product (VISITview lesson | PowerPoint) — derived using MTSAT-2 data — indicated that downwind portions of the ash cloud reached the 18-20 km ASL range (black color enhancement), with a maximum ash height value of 22 km (below; click image to play animation). CALIOP data from a CALIPSO overpass of the Kelut volcanic cloud just around 18:13 UTC on 13 February showed that the top of the volcanic cloud was generally at an altitude of 18-19 km, with some cloud/ash material reaching a maximum height of 26 km; taking that data source into consideration, a subsequent volcanic ash advisory issued by the Darwin VAAC at 17:09 UTC on 14 February revised the maximum ash height to 65,000 feet or 19.8 km.

MTSAT-2 Volcanic Ash Height product (click to play animation)

MTSAT-2 Volcanic Ash Height product (click to play animation)

With the arrival of early morning daylight, MTSAT-1R 0.68 µm visible channel images (below) showed the dense volcanic ash plume drifting west-southwestward; there was also a subtle signature of the “bow shock waves” seen along the eastern edge of the ash plume, similar to what was observed on the IR imagery.

MTSAT-1R 0.68 µm visible channel images

MTSAT-1R 0.68 µm visible channel images

Back to the topic of the 26 km height seen on the CALIPSO data: on the 10-minute interval MTSAT-1R 10.8 µm IR imagery, the warmest cloud-top IR brightness temperature within the “circular warm spot” of the volcanic cloud was -56ºC at 17:19 UTC. The 13 February/12 UTC Surabaya/Juanda rawinsonde only made it up to 64.9 mb or 19.02 km (where it was -71.3ºC) — however, the 14 February/00 UTC rawinsonde ascended all the way to 10 mb (below). So using this later sounding, the air temperature of -56ºC corresponded to an height somewhere between 24.9 mb (24.8 km) and 20 mb (26.2 km) — which roughly agrees with the 26 km height seen on the CALIOP data.

Surabaya/Juanda rawinsonde data (00 UTC on 14 February)

Surabaya/Juanda rawinsonde data (00 UTC on 14 February)

Additional satellite products showing details of the Kelut volcanic eruption can be found on Nicarnica Aviation blog posts (1 | 2).

 

Eruption of the Tungurahua volcano in Ecuador

February 2nd, 2014
GOES-13 false-color RGB images (click to play animation)

GOES-13 false-color RGB images (click to play animation)

After 2 days of renewed activity, the Tungurahua volcano in Ecuador produced some minor eruptions punctuated by a single large eruption on 01 February 2014. GOES-13 false-color Red/Green/Blue (RGB) images specifically tailored to help identify and track volcanic features (above; click image to play animation) showed (1) the southeastward drift of the initial volcanic plume (estimated to be as high as 26,000 feet) from 19:45 – 22:15 UTC, followed by (2) the rapid expansion and southward drift of the larger volcanic plume (estimated to be as high as 45,000 feet) after 22:45 UTC, and (3) another smaller volcanic plume (estimated to be as high as 23,000 feet) drifting southeastward after 02:45 UTC on 02 February.

McIDAS images of GOES-13 3.9 µm shortwave IR data (below; click image to play animation) revealed the presence of a distinct “hot spot” (dark black to yellow to red enhancement) at the summit of the volcano after 22:45 UTC — the hottest pixel detected was 338.5 K or 66.4º C at 00:45 UTC on 02 February.

GOES-13 3.9 µm shortwave IR images (click to play animation)

GOES-13 3.9 µm shortwave IR images (click to play animation)

As the sun was setting, the rapidly-rising volcanic ash plume associated with the stronger eruption cast a long shadow toward the east-northeast on the 22:45 UTC GOES-13 0.63 µm visible channel image (below).

GOES-13 0.63 µm visible channel image

GOES-13 0.63 µm visible channel image

Chaparrastique erupts in El Salvador

December 29th, 2013
GOES-13 0.63 µm visible imagery during Chaparrastique eruption (click to play animation)

GOES-13 0.63 µm visible imagery during Chaparrastique eruption (click to play animation)

The volcano Chapparastique in eastern El Salvador near the city of San Miguel experienced a brief eruption on Sunday the 29th of December (YouTube video). Half-hourly 0.63 µm visible channel imagery from GOES-13 or GOES-East (the most frequent imagery available at 13.5º N, the latitude of the volcano), above, plainly shows the appearance of the volcanic ash cloud between 16:15 and 16:45 UTC (media sources reported that the time of the eruption was 16:32 UTC). Most of the ash cloud then moved westward across the coast and over the adjacent waters of the Pacific Ocean, although parts of the ash cloud also moved eastward over Honduras. This is the first complete Chapparastique advisory from the VAAC in Washington DC on this eruption. The most recent volcanic ash advisories can be found here.

GOES-15 or GOES-West, positioned at 135º W, was also able to view the ash cloud, and that animation is below. El Salvador is near the eastern edge of the satellite view. Routine scanning that was taking place on Sunday 29 December only viewed El Salvador every three hours.

GOES-15 0.63 µm visible imagery during Chaparrastique eruption (click to play animation)

GOES-15 0.63 µm visible imagery during Chaparrastique eruption (click to play animation)

It happens occasionally that useful information about volcanic eruptions can be gleaned from extreme limb views from geostationary satellites (see here, for example, or this animation from this blog post). In the present case, the MTSAT-2 visible imagery, below, was a bit too far to the west to view the atmosphere over central America.

MTSAT-2 0.73 µm visible imagery during Chaparrastique eruption (click to play animation)

MTSAT-2 0.73 µm visible imagery during Chaparrastique eruption (click to play animation)

Meteosat-10 data possibly saw the eruption; however, the remapped imagery that is broadcast does not include pixels for which a latitude/longitude value can be computed, such as pixels that are at the extreme edge of the limb, in outer space. To ascertain the presence of a signal in the satellite data would require access to the raw data from the satellite, and that is not routinely available. Meteorsat-10 visible images surrounding the eruption time are shown below.

METEOSAT-10 0.6 µm visible imagery during Chaparrastique eruption (click to play animation)

METEOSAT-10 0.6 µm visible imagery during Chaparrastique eruption (click to play animation)

Note that when GOES-R ABI is broadcasting data, its limb edge will resemble the METEOSAT-10 data above rather than the more complete MTSAT-2 data. Level 0 data from ABI includes space looks at the limb; that level 0 data will be calibrated, navigated and remapped and distributed as level 1 GOES-R series ReBroadcast (GRB) data that will not include points at the limb that are un-navigable (but that nevertheless can include interesting data).

As part of CIMSS/ASPB participation in GOES-R Proving Ground activities, various volcanic ash detection and analysis products have been developed. Below is an animation of GOES-13 multi-spectral false-color Red/Green/Blue (RGB) images that also show the dispersion of the volcanic ash cloud.

GOES-13 multi-spectral RGB images (click to play animation)

GOES-13 multi-spectral RGB images (click to play animation)

Examples of some of the quantitative volcanic ash products are shown below, using MODIS data from an overpass of the Aqua satellite at 18:50 UTC. The maximum ash height appeared to be around 10 km along the eastern end of the cloud; the maximum ash loading approached 6 g/m2 on the western edge of the plume; the maximum ash particle effective radius was in the 14-16 µm range along the edges of the cloud.

Aqua MODIS Ash/Dust Cloud Height product

Aqua MODIS Ash/Dust Cloud Height product

Aqua MODIS Ash/Dust Loading product

Aqua MODIS Ash/Dust Loading product

Aqua MODIS Dust/Ash Particle Effective Radius product

Aqua MODIS Dust/Ash Particle Effective Radius product

Re-suspended ash from the Cordón Caulle volcano in Chile?

December 14th, 2013
GOES-13 0.63 µm visible channel images (click to play animation)

GOES-13 0.63 µm visible channel images (click to play animation)

On the morning of 14 December 2013, GOES-13 0.63 µm visible channel images (above; click image to play animation) showed what appeared to be a plume of re-suspended volcanic ash moving northward from the region of the Cordón Caulle volcano in Chile. As the airborne ash plume begain to disperse later in the day, it then began to move in a more northeasterly direction. Since no volcanic ash advisories were issued by the Beunos Aires Volcanic Ash Advisory Center (VAAC), it was assumed that this was a case of re-suspended ash that covered the ground following previous eruptions.

Although there is not always a thermal anomaly or “hot spot” seen on shortwave IR satellite images accompanying a volcanic eruption, no such hot spot was seen on the corresponding GOES-13 3.9 µm shorwave IR imagery (below; click image to play animation). The higher terrain of the Cordón Caulle volcano complex — located in the center of the images — initially appeared cooler (lighter gray) prior to sunrise, but then their higher-elevation surfaces begain to warm (darker gray pixels) after sunrise. The plume of re-suspended volcanic ash also exhibited a darker appearance after sunrise, due to the reflection of solar radiation off the small particles.

GOES-13 3.9 µm shortwave IR images (click to play animation)

GOES-13 3.9 µm shortwave IR images (click to play animation)

Quantitative products derived from Terra MODIS imagery (below) indicated that the plume had a maximum height of around 5-6 km, with ash/dust loading in the 4-5 g/m2 range, and a mean particle effective radius as large as 4-6 µm.

Terra MODIS Ash Height product

Terra MODIS Ash Height product

Terra MODIS Ash/Dust Loading product

Terra MODIS Ash/Dust Loading product

Terra MODIS Ash Particle Effective Radius product

Terra MODIS Ash Particle Effective Radius product