Re-suspended volcanic ash from the Novarupta volcano in Alaska

September 29th, 2014
GOES-15 0.63 µm visible channel images (click to play animation)

GOES-15 0.63 µm visible channel images (click to play animation)

McIDAS images of GOES-15 0.63 µm visible channel data (above; click image to play animation) showed the hazy signature of a plume of re-suspended volcanic ash originating from the region of the Novarupta volcano in Alaska, moving southeastward over the Shelikof Strait toward Kodiak Island on 29 September 2014. The 1912 eruption of Novarupta left a very deep deposit of volcanic ash, which often gets lofted by strong winds in the early Autumn months before snowfall covers the ash (another example occurred on 22 September 2013). Surface winds gusted as high as 30 knots at regional reporting stations, with numerical models estimating terrain-enhanced winds as high as 40-50 knots over the Novarupta ash field.

An AWIPS II image of POES AVHRR 0.86 µm visible channel data (below) showed the ash plume at 22:46 UTC; a pilot report at 22:45 UTC indicated that the top of the ash plume was between 4000 and 6000 feet above ground level.

POES AVHRR 0.86 µm visible channel image, with METAR surface reports and Pilot reports (PIREPs)

POES AVHRR 0.86 µm visible channel image, with METAR surface reports and Pilot reports (PIREPs)

A sequence of 3 Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images from the SSEC RealEarth web map server (below) indicated that the re-suspended ash plume had been increasing in areal extent during that period.

Suomi NPP VIIRS true-color images from 27, 28, and 29 September

Suomi NPP VIIRS true-color images from 27, 28, and 29 September

A sequence of 4-panel products from the NOAA/CIMSS Volcanic Cloud Monitoring site (below) shows False-color images, Ash/dust cloud height, Ash/dust particle effective radius, and Ash/dust loading (derived from either Terra/Aqua MODIS or Suomi NPP VIIRS data).

4-panel MODIS/VIIRS products: False color image; Ash/dust cloud height; Ash/dust particle effective radius; Ash/dust loading

4-panel MODIS/VIIRS products: False color image; Ash/dust cloud height; Ash/dust particle effective radius; Ash/dust loading

Hat tip to Mark Ruminski (NOAA/NESDIS) for alerting us to this event.

Eruption of the Mount Ontake volcano in Japan

September 27th, 2014
Suomi NPP VIIRS true-color images on 27, 28, and 29 September

Suomi NPP VIIRS true-color images on 27, 28, and 29 September

The Mount Ontake volcano erupted on the main Japanese island of Honshu around 02:52 UTC (11:52 AM local time) on 27 September 2014. A sequence of three daily (27, 28, and 29 September) Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images from the SSEC RealEarth web map server (above) showed the volcanic plume drifting eastward then southeastward during that period. The ash plume disrupted air travel in some parts of Japan.

A comparison of pre-eruption (22 September) and post-eruption (28 September) VIIRS true-color images (below) revealed the light gray signature of thick volcanic ash covering the region around the summit of Mount Ontake. There was also a narrow volcanic plume streaming southeastward on the 28 September image.

22 September vs 28 September VIIRS true-color images

22 September vs 28 September VIIRS true-color images

Eruption of the Sangeang Api volcano in Indonesia

May 30th, 2014
MTSAT-2 0.63 µm visible channel and 10.8 µm IR channel images at 08:32 UTC

MTSAT-2 0.63 µm visible channel and 10.8 µm IR channel images at 08:32 UTC

A comparison of McIDAS images of MTSAT-2 0.63 µm visible channel and 10.8 µm IR channel data at 08:32 UTC on 30 May 2014 (above) showed the volcanic cloud from the first in a series of eruptions of the Sangeang Api volcano in Indonesia (aircraft photos). The coldest cloud-top IR brightness temperature at that time was -74.5º C; note that the tall volcanic cloud was casting a large shadow toward the east-southeast in the visible image.

An animation of MTSAT-2 10.8 µm IR images (below; click image to play animation; also available as an MP4 movie file) revealed that there were a number of smaller eruptions that followed the initial, larger eruption.

MTSAT-2 10.8 µm IR channel images (click to play animation)

MTSAT-2 10.8 µm IR channel images (click to play animation)

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MTSAT-2 false-color RGB images (click to play animation

MTSAT-2 false-color RGB images (click to play animation)

The NOAA/CIMSS Volcanic Cloud Monitoring MTSAT-2 false-color Red/Green/Blue (RGB) images (above; click image to play animation) showed the southeastward spread of volcanic ash cloud from the first 2 eruptions, while the Volcanic Ash Height product (below; click image to play animation) indicated that the ash may have reached altitudes of at least 12-14 km. Pilot reports in the vicinity placed the height of the volcanic cloud at 65,000 feet or 19.8 km.

NOAA/CIMSS Volcanic Ash Height product (click to play animation)

NOAA/CIMSS Volcanic Ash Height product (click to play animation)

Night-time McIDAS-V images of Suomi NPP VIIRS 11.45 µm IR, 3.9 µm shortwave IR, and 0.7 µm Day/Night Band (DNB) images of one of the secondary eruptions at 17:43 UTC on 30 May (below; courtesy of William Straka, SSEC) showed a cloud-top IR brightness temperature as cold as -77º C, along with the yellow-enhanced “hot spot” on the shortwave IR and the bright glow on the DNB image from the hot volcano vent and lava flows.

Suomi NPP VIIRS 11.45 µm IR, 3.9 µm shortwave IR, and 0.7 µm Day/Night Band images

Suomi NPP VIIRS 11.45 µm IR, 3.9 µm shortwave IR, and 0.7 µm Day/Night Band images

A composite of Suomi NPP VIIRS true-color RGB images from 31 May, viewed using the SSEC RealEarth web map server (below) showed the widespread extent of the volcanic ash cloud from the ongoing eruption.

Suomi NPP VIIRS true-color RGB image composite

Suomi NPP VIIRS true-color RGB image composite

Due to the southeastward drift of the primary volcanic ash plume toward Australia, flights were cancelled at the Darwin airport. MTSAT-2 visible and IR images with polygons of Volcanic Ash Advisories are shown below (click image to play animation).

MTSAT-2 visible and IR images, with Volcanic Ash Advisory polygons

MTSAT-2 visible and IR images, with Volcanic Ash Advisory polygons

===== 01 June Update =====

A comparison of Suomi NPP VIIRS true-color images from 31 May and 01 June (below) showed that while the eruption was still ongoing, the amount of ash output had dramatically decreased.

Suomi NPP VIIRS true-color images

Suomi NPP VIIRS true-color images

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).