Numerous wildfires were burning near Concepción, Chile during the 02 February – 04 February 2023 period (media report) — GOES-16 (GOES-East) CIMSS Natural Color RGB images combined with the Fire Power derived product (above) showed the diurnal variation of fire thermal signatures along with the dense daytime smoke plumes. The maximum Fire Power values exceeded 2500 MW with some of the larger fires. Surface reports in the vicinity of the wildfires were sparse and intermittent, but did indicate reductions in visibility due to the dense smoke.

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According to NOAA’s Great Lakes Surface Environmental Analysis (GLSEA) the Great Lakes were 11.6% ice covered on February 2nd when an arctic air mass was descending southward over the region. The cold air boosted ice coverage to 14.7% on February 3rd, less than half of the average extent (1973-2022) of 34% for February 3rd. This meant ample open waters for lake-effect clouds and snow, per the 5-hour GOES East animation below.

Ice extent on the Great Lakes is highly variable. In the past five years ice coverage on February 3rd has been as low as 5.3% in 2020 and as high as 40.9% in 2019. Records have been kept since 1973. (Check current conditions via https://coastwatch.glerl.noaa.gov/ice.html)

In spite of wide year-to-year variability, studies show a downward trend in Great Lakes ice coverage since records began.

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At around 9 PM EST on 03 February 2023 (0200 UTC on 04 February) a 50-car train derailed in East Palestine in far eastern Ohio, with some of the rail cars carrying hazardous chemicals that caught fire (media report) — and GOES-16 (GOES-East) Shortwave Infrared (3.9 µm) images (above) showed the thermal signature of this long-lived fire, which was still evident 27 hours after the derailment (at 0006 UTC on 05 February). At times, thick cloud cover totally obscured the thermal signature; however, when relatively thin clouds were over the fire this thermal signature could still be seen. The peak 3.9 µm infrared brightness temperature was 17ºC, about an hour after the accident (at 0306 UTC).

===== 06 February Update =====

On the afternoon of 06 February, a controlled vent and burn of toxic chemicals (contained in 5 of the rail cars) was conducted (media report) — and 1-minute Mesoscale Domain Sector GOES-16 “Red” Visible (0.64 µm), Shortwave Infrared, Cloud Top Phase derived product, “Clean” Infrared Window (10.3 µm), Cloud Top Temperature derived product and Cloud Top Height derived product (above) showed signatures of the resulting black smoke plume that penetrated the top of a supercooled water droplet (light green in the Cloud Top Phase product) stratus cloud layer that was over the area at that time. The black smoke plume first emerged from the cloud top at 2139 UTC, casting a long shadow to the northeast at 2140 UTC. Beginning at 2149 UTC, the Clear Sky Mask derived product (animated GIF | MP4) mistakenly identified the black smoke as a hole in the stratus cloud deck — so with a “Clear” sky falsely indicated, the derived cloud products (Cloud Top Phase / Cloud Top Temperature / Cloud Top Height) were not created for those particular pixels. Note that the Cloud Top Height product was distributed in AWIPS at a reduced spatial resolution (4 km, compared to the native resolution of 2 km for infrared spectral bands used to create the product).

The black smoke cloud seen in Visible imagery also exhibited a signature in Dust RGB and Split Cloud Top Phase brightness temperature difference imagery (below) — which both leverage the 8.5 µm spectral band that is sensitive to differences in emissivity (in this case, the emissivity of the smoke particles differed from that of the supercooled water droplets along the top of the surrounding stratus cloud layer) .

The infrared brightness temperature of the overshooting black smoke plume was 1-2ºC warmer than that of the adjacent underlying stratus cloud layer — and a plot of rawinsonde data from Pittsburgh, Pennsylvania (below) revealed the presence of a strong boundary layer temperature inversion, with air temperatures rising quickly with height. The presence of light winds at those low altitudes also prevented a rapid dispersion or significant advection of the above-stratus smoke plume.

GOES-16 True Color RGB images from the CSPP GeoSphere site (below) provided a better portrayal of the contrast between the dark black smoke plume and the surrounding stratus cloud deck.

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After a prolonged 3-day winter storm that produced highly disruptive accumulations of sleet and freezing rain (WPC Storm Summary) across parts of the Southern Plains and Mid-South from 31 January – 02 February 2023, clouds cleared out across much of those regions on 03 February — allowing GOES-16 (GOES-East) “Red” Visible (0.64 µm) and Day Snow-Fog RGB images (above) to depict some of the areas where significant ice accrual occurred.

The Day Snow-Fog RGB imagery is more useful here, because it leverages the 1.61 µm “Snow/Ice” spectral band. As seen in a plot of ABI Spectral Response Functions (below), snow and ice are efficient absorbers of radiation (and therefore exhibit a low reflectance) at the 1.61 µm wavelength — making those features appear as shades of red in the RGB images (and since ice absorbs even more strongly than snow, ice appears as the darkest shades of red).

Due to the translucent nature of thicker ice accrual (providing that it is not covered with a layer of light snow), note that some areas of significant ice accrual are not as apparent in the Visible imagery as they are in the RGB imagery — in particular, over parts of western Tennessee, far northwestern Mississippi and southern Arkansas (as shown in a GOES-16 image comparison at 1616 UTC and a NOAA-20 image comparison at 1831 UTC, below).

Other blog posts documenting the identification of areas with significant ice accrual can be found here.

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