Undular bore and industrial plumes in Minnesota

December 11th, 2020 |

GOES-16 Day Snow-Fog RGB,

GOES-16 Day Snow-Fog RGB, “Red” Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images [click to play animation | MP4]

GOES-16 (GOES-East) Day Snow-Fog Red-Green-Blue (RGB), “Red” Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images (above) showed and undular bore propagating slowly north-northwestward across northeastern Minnesota and western Lake Superior on 11 December 2020. Also evident on the RGB and 1.61 µm images was the presence of a few industrial plumes — with their point sources being north of Hibbing — moving south-southwestward. These plume sources were likely large coal-fired power plants and other industrial sites located across that region; emissions from these industrial sources acted as cloud condensation nuclei, causing a higher concentration of smaller supercooled cloud droplets downwind of each plume source.

In a comparison of Suomi NPP VIIRS Visible (0.64 µm), Near-Infrared (1.61 µm) and Shortwave Infrared (3.74 µm) images at 1734 UTC (below), the industrial plumes appeared warmer (shades of green) due to enhanced reflection of incoming solar radiation by the smaller cloud droplets within the plumes.

Suomi NPP VIIRS Visible (0.64 µm), Near-Infrared (1.61 µm) and Shortwave Infrared (3.74 µm) images at 1734 UTC [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm), Near-Infrared (1.61 µm) and Shortwave Infrared (3.74 µm) images at 1734 UTC [click to enlarge]

Plots of rawinsonde data from International Falls, Minnesota (below) depicted a strong temperature inversion based around 1.2 km — the undular bore was likely ducted within this inversion.

Plot of rawinsonde data from International Falls, Minnesota [click to enlarge]

Plots of rawinsonde data from International Falls, Minnesota [click to enlarge]

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