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)

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)

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)

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)

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 Loading product

Aqua MODIS Dust/Ash Particle Effective Radius product

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Terra and Aqua MODIS true-color RGB images

After a cold night (morning low temperatures of -24ºF were recorded at several inland locations in Wisconsin, along with -12ºF in northern Illinois), ice was seen forming in the western and southern nearshore waters of Lake Michigan on 24 December 2013. The ice motion could be seen on consecutive 250-meter resolution Terra and Aqua MODIS true-color Band 1/4/3 Red/Green/Blue (RGB) images from the SSEC MODIS Today site (above).

A comparison of the Aqua MODIS true-color and Band 7/2/1 false-color RGB images (below) confirms that the brighter features seen along the western and southern nearshore waters were ice — ice and snow (as well as clouds composed of ice crystals) appear as varying shades of cyan in the false-color image, in contrast to supercooled water droplet clouds which appear as varyinng shades of white.

Aqua MODIS true-color and false-color RGB images

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Suomi NPP VIIRS 0.64 µm visible channel and false-color snow/ice-vs-cloud RGB images

A large portion of central and southwestern Oklahoma experienced a signifcant freeezing rain event during the 20 December – 21 December 2013 period, as abundant moisture moved over shallow cold air at the surface (NWS Norman OK event summary). On the following day, as clouds began to clear across the region, AWIPS images of Suomi NPP VIIRS 0.64 µm visible channel data and the corresponding false-color Red/Green/Blue (RGB) product (above) revealed a broad swath of snow on the ground that stretched from the New Mexico/Texas border northeastward across Kansas (where as much as 15 inches fell) and into southeastern Nebraska and northwestern Missouri.

The false-color “snow/ice-vs-cloud discrimination” RGB image used the VIIRS instrument 0.64 µm visible channel and the 1.61 µm “snow/ice channel”, taking advantage of the fact that snow and ice are strong absorbers of radiation at the 1.61 µm wavelength (and therefore appear darker on that particular image). The result of this image combination shows snow cover as varying shades of red, with significant ice accretion on the ground showing up as the darkest shades of red. These darker shades of red in central and southwestern Oklahoma corresponded to the area between Clinton (KCSM) and Oklahoma City (KOKC) which received as much as 0.75 to 1.00 inch of ice accretion. The weight of this thick layer of ice caused widespread downed trees and powerlines, with power outages at several locations. Note that the significant glaze of ice on the ground  — for example, in areas surrounding Clinton (KCSM) and Hobart (KHBR) — did not show up particularly well on the visible image, since an ice layer is generally translucent in appearance as viewed from above (unless covered with a thin layer of snow, as was the case farther to the north).

Through holes in the clouds, there were some hints of darker red seen in southeastern Kansas, where significant accrual of ice also occurred.

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

Strong southerly winds (gusting over 30 mph) generated a plume of blowing dust that originated in far northeastern Mexico and moved over Deep South Texas on the afternoon hours of 19 December 2013. McIDAS images of GOES-13 0.63 µm visible channel data (above; click image to play animation) showed the plume as it moved northward; surface visibility dropped as low as 2.5 miles at Jim Hogg Country Airport (station identifier KHBV) at 23:35 UTC.

A signal of the airborne dust plume was evident on an AWIPS image of the MODIS 11-12 µm IR brightness temperature difference (below). At the time of the MODIS image the surface visibility had dropped to 5 miles at McAllen, Texas (station identifier KMFE).

MODIS 11-12 µm IR brightness temperature difference

The hazy tan signature of the blowing dust plume was also quite evident on the corresponding 250-meter resolution MODIS true-color Red/Green/Blue (RGB) image (below).

Aqua MODIS true-color RGB image

The POES AVHRR Cloud Top Height product at 20:55 UTC (below) indicated that the top of the blowing dust plume was at 2 km above ground level.

POES AVHRR Cloud Top Height product

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