![\"\"](\"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/images\/2023\/04\/230423_goes18_nighttimeMicrophysicsRGB_trueColorRGB_FD_Katmai_AK_resuspended_ash_anim.gif\")
<\/a>10-minute GOES-18 Nighttime Microphysics RGB + daytime True Color RGB images [click to play animated GIF | MP4<\/strong><\/a>]<\/p><\/div>10-minute Full Disk sector GOES-18 (GOES-West)<\/em> Nighttime Microphysics RGB<\/strong><\/a> + daytime True Color RGB images from the CSPP GeoSphere<\/strong><\/a> site (above)<\/strong><\/em> showed a plume of resuspended ash (from the 1912 Novarupta-Katmai<\/strong><\/a> eruption in Alaska) that was being transported offshore across the Shelikof Strait<\/strong><\/a> toward Kodiak Island — and wrapping into an eddy circulation within the Strait on 23 April 2023.<\/p>\n The entrainment of resuspended ash within the eddy circulation was more apparent in 1-minute Mesoscale Domain Sector<\/strong><\/a> GOES-18 Nighttime Microphysics + daytime True Color RGB images (below)<\/strong><\/em>.<\/p>\n 1-minute GOES-18 Nighttime Microphysics + daytime True Color RGB images [click to play animated GIF | MP4<\/strong><\/a>]<\/p><\/div>1-minute GOES-18 Dust RGB<\/strong><\/a> images (below)<\/strong><\/em> include plots of surface\/buoy\/ship reports and GOES-18 Derived Motion Winds<\/strong><\/a> — note how the wind direction at Shelikof Strait Buoy 46077<\/strong><\/a> changed as the eddy circulation developed. Derived Motion Winds indicated that portions of the offshore resuspended ash plume were moving at speeds up to 20 knots.<\/p>\n GOES-18 Dust RGB images [click to play animated GIF | MP4<\/strong><\/a>]<\/p><\/div>A toggle between GOES-18 Dust RGB and Topography images (below)<\/strong><\/em> showed that the plume was emerging from the ash-filled Valley Of Ten Thousand Smokes<\/strong><\/a>.<\/p>\n GOES-18 Dust RGB and Topography images [click to enlarge]<\/p><\/div>Since this particular plume was composed of a mixture of aged ash and more recent sediment from glacial melt (rather than purely fresh volcanic ash), the Dust RGB did a better job at highlighting the plume — as seen in a comparison of Ash RGB<\/strong><\/a> and Dust RGB<\/strong><\/a> images at 1500 UTC and 1600 UTC (below)<\/strong><\/em>. Although the two RGBs use the same spectral bands, they are scaled differently (in order to better depict typical ash or dust features).<\/p>\n Comparison of Ash RGB and Dust RGB images at 1500 UTC and 1600 UTC [click to enlarge]<\/p><\/div>RCM-1 Synthetic Aperture Radar (SAR) winds (source<\/strong><\/a>) at 1646 UTC (below)<\/strong><\/em> revealed the area of lighter wind speeds (darker shades of blue) within the eddy circulation over the Shelikof Strait.<\/p>\n<\/a><\/a><\/a><\/a>