True-color RGB images from Terra MODIS, Suomi NPP VIIRS and Aqua MODIS, viewed using RealEarth (below) revealed the long ash plume during the late morning and early afternoon on 25 March. The dark signature of ash fall onto the snow-covered terrain was evident on the Terra and Aqua images, just west of the high-altitude ash plume.26 March Update: a closer view of Terra MODIS true-color images from 25 and 26 March (below) showed that the perimeter of the darker gray surface ash fall signature had fanned out in both the west and east directions.
Multispectral Red/Green/Blue (RGB) images from the NOAA/CIMSS Volcanic Cloud Monitoring site (below) displayed a signal of the volcanic cloud during the ~2.5 hours following the onset of the eruption — since this particular RGB combination uses the 3.9 µm Shortwave Infrared band, the volcanic cloud feature appeared as darker shades of magenta during the first few images while reflected solar illumination was present before sunset.Another variant of RGB images (below) uses the 8.5 µm “cloud top phase” band, which is also sensitive to SO2 absorption; in this case, the appearance of the volcanic cloud feature was dominated by shades of yellow, indicating high levels of SO2. A comparison of the 3 Himawari-8 water vapor bands (below) showed that a strong signature of the volcanic cloud was seen on the lower-tropospheric 7.3 µm band; this was due to the fact that the 7.3 µm band is also sensitive to elevated levels of SO2 loading in the atmosphere (which was also noted at the bottom of this Mount Pavlof eruption blog post). These same 3 water vapor bands (Upper-level, Mid-level and Lower-level) will be available from the GOES-R series ABI instrument. A closer view using Himawari-8 false-color images (below) includes a magenta polygon surrounding the volcanic cloud soon after the onset of the eruption — this is an example of an experimental automated volcanic eruption alerting system. According to Michael Pavolonis (NOAA/NESDIS), “Using our automated cloud object tracking algorithm, the eruption produced a cloud at 01:30 UTC that was about 19 deg C colder than the background imaged by Himawari-8 at 01:20 UTC. Taking into account the pixel size, background cloud cover, and time interval between successive images, the 19 deg C change is about an 11 standard deviation outlier relative to a very large database of meteorological clouds. The vertical growth anomaly calculation is the basis of one the components of our experimental automated volcanic eruption alerting system”. The creation of RGB images such as those shown above will be possible from the GOES-R series of satellites (beginning with GOES-16), since the ABI instrument has the 8.4 µm and 12.3 µm bands that are not available from the current generation of GOES imager instruments.
Additional satellite images of this event are available from NWS Anchorage.
A closer view of the GMS-4 Infrared Window (11.5 µm) images (below) revealed interesting characteristics of the volcanic plume which penetrated the tropopause (which was at an air temperature of around -83º C, according to nearby rawinsonde reports) during the 3-8 hours following the onset of the 0227 UTC eruption. Note the initial appearance of a small area of very warm IR cloud-top IR brightness temperatures (-21.6º C at 0631 UTC, and -25.7º C at 0730 UTC) which then blossomed outward and became a westward-moving stratospheric plume that was notably warmer than the majority of the cold volcanic cloud canopy (which exhibited IR brightness temperatures in the -80º to -90º C range, denoted by the violet to yellow color enhancement).
———————————————————————————————————-A higher-resolution (1.1-km) view of the post-eruption cloud was provided by NOAA-10 AVHRR images at 1034 UTC on 15 June (above). Even though it was just past sunset over the Philippines, the narrow stratospheric plume could be seen towering above the canopy of the main volcanic cloud (the plume was at a high enough altitude — estimated at a maximum of 40 km (reference 1 | reference 2) — to still be illuminated by sunlight). The summit of Pinatubo is located 8.7 miles/14 km west-southwest of what was then Clark Air Force Base (station identifier RPLC). On the 10.8 µm Infrared Window image, cloud-top gravity waves could be seen propagating radially outward from the overshooting top located above the volcano (which exhibited a minimum IR brightness temperature of -86º C, violet color enhancement). Note the much warmer IR brightness temperatures (as warm as -31º C, green color enhancement) associated with the stratospheric plume just off the west coast of Luzon. A closer view is available here.
About 10 hours prior to the climactic eruption, a volcanic ash cloud from one of the earlier eruptions was captured by NOAA-10 AVHRR images at 2329 UTC on 14 June (below). Around this same time it can be seen that Yunya was making landfall as a minimal-intensity typhoon along the eastern coast of Luzon. A closer view is available here.
GOES-3 started service on 16 June 1978 and was the operational GOES-West satellite until the late 1980s. Having lost imaging capabilities, it started a second long life as a communications satellite; GOES-3 is currently the oldest operating satellite. Decommissioning will begin on 8 June and run for 15 days. If final decommissioning happens as planned on 23 June, GOES-3’s service life will be 38 years, 7 days.
GOES-3’s arguably most famous imagery occurred during the eruption of Mount St. Helens on 18 May 1980, shown above (click here for an animation of the eruption, courtesy of Barry Roth, SSEC; Tim Schmit, NOAA/ASPB also provided longer visible animations: MP4 | animated GIF).
A comparison of GOES-3 Visible (0.65 µm) and Infrared Window (11.5 µm) images, below, showed that a large portion of the volcanic cloud exhibited IR brightness temperatures of -60º C (dark red color enhancement) or colder as the feature moved rapidly eastward during the first 10 hours following the eruption. It is interesting to note that an “enhanced-V” or cold/warm (-65º/-47º C) thermal couplet signature was evident on the initial 1545 UTC Infrared image (zoom), as the volcanic ash cloud rapidly rose to an estimated altitude of 12 to 16 miles (20 to 27 km) above sea level.Some early examples of full disk GOES-3 images (on 20 November 1978) are shown below, courtesy of Tim Schmit, NOAA/ASPB.