![](\"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/images\/2023\/10\/231003_goes18_ashRGB_so2RGB_Shishaldin_AK_anim.gif\")
<\/a>GOES-18 Ash RGB images (top) and SO2 RGB images (bottom), with plots of Pilot Reports and Volcanic Ash Advisory\/Forecast polygons, from 1250-1910 UTC [click to play animated GIF | MP4<\/strong><\/a>]<\/p><\/div>GOES-18\u00a0(GOES-West)<\/em>\u00a0SO2 RGB<\/strong><\/a>\u00a0and\u00a0Ash RGB<\/strong><\/a>\u00a0images\u00a0(above)<\/strong><\/em> showed the complex transport of a volcanic cloud produced by an explosive eruption of Mount Shishaldin<\/strong><\/a> that began around 1350 UTC on 03 October 2023. The bulk of the higher-altitude volcanic cloud was rich in SO2 (shades of yellow in both RGB types), while a smaller mid-level portion that had high ash content exhibited shades of reddish-brown in the Ash RGB (and shades of blue to pink in the SO2 RGB images).<\/p>\n 2 Pilot Reports (PIREPs) issued shortly after the eruption onset indicated an ash height of 21000 ft at 1400 UTC, and 40000 ft at 1446 UTC (below)<\/strong><\/em>.<\/p>\n GOES-18 Ash RGB (top) and SO2 RGB (bottom) images at 1400 UTC, with cursor sampling of a of Pilot Report issued at 1400 UTC [click to enlarge]<\/p><\/div>\n GOES-18 Ash RGB (top) and SO2 RGB (bottom) images at 1450 UTC, with cursor sampling of a of Pilot Report issued at 1446 UTC [click to enlarge]<\/p><\/div>In Nighttime Microphysics RGB\u00a0 + daytime True Color RGB images from the\u00a0CSPPGeoSphere<\/strong><\/a>\u00a0site\u00a0(below)<\/strong><\/em>, after sunrise the ash-rich portion of the volcanic cloud exhibited shades of tan to darker brown, as it moved to the south-southwest.<\/p>\n GOES-18 Nighttime Microphysics RGB + daytime True Color RGB images, from 1210-2140 UTC [click to play MP4 animation]<\/p><\/div>A radiometrically retrieved Volcanic Ash Cloud Height product from the NOAA\/CIMSS Volcanic Cloud Monitoring<\/strong><\/a>\u00a0site\u00a0(below)<\/strong><\/em> indicated that parts of the volcanic cloud may have reached heights in the 18-20 km range (black enhancement) within 20 minutes of the eruption onset.<\/p>\n Volcanic Cloud Ash Height derived product, from 1330-1700 UTC [click to play animated GIF | MP4<\/strong><\/a>]<\/p><\/div> Suomi-NPP VIIRS Day\/Night Band (0.7 \u00b5m) and Infrared Window (11.45 \u00b5m) images, valid at 1404 UTC [click to enlarge]<\/p><\/div>About 14 minutes after the explosive eruption began, a toggle between Suomi-NPP VIIRS Day\/Night Band (0.7 \u00b5m) and Infrared Window (11.45 \u00b5m) images valid at 1404 UTC<\/strong><\/a> (above)<\/strong><\/em> revealed that the coldest cloud-top infrared brightness temperature was -64.37\u00baC<\/strong><\/a> (cyan color enhancement) — while the hot lava flows spreading away from the summit of Shishaldin exhibited surface infrared brightness temperatures as high as 106.85\u00baC<\/strong><\/a> (darker black enhancement).<\/p>\n The -64.37\u00baC cloud-top infrared brightness temperature was indicative of a significant air parcel overshoot of the local tropopause — which was -50.5\u00baC at an altitude of 9292.4 m (30486.9 ft) according to 1200 UTC rawinsonde data<\/strong><\/a> from nearby Cold Bay, Alaska (below)<\/strong><\/em>.<\/p>\n Plot of rawinsonde data from Cold Bay, Alaska at 1200 UTC [click to enlarge]<\/p><\/div>On a side note, a toggle between Infrared Window images from Suomi-NPP and GOES-18 (below)<\/strong><\/em> showed (1) the large northwest parallax<\/strong><\/a> offset associated with GOES-18 imagery at such high latitudes, which would be about 35 km or 22 mi for a 50 kft cloud top feature<\/strong><\/a> in the vicinity of Shishaldin, and (2) the significantly colder cloud-top infrared brightness temperature sensed with the higher spatial resolution VIIRS instrument (375 m, vs the nominal 2 km at satellite sub-point for GOES-18 ABI).<\/p>\n<\/a><\/a><\/a><\/a>
\n<\/a><\/a>