Mostly clear skies over the Great Lakes and a near-Full Moon allowed the Suomi NPP VIIRS Day/Night Band (DNB) imager to record the remaining extent of ice on the five Great Lakes with remarkable clarity at night.

Portions of Georgian Bay (Lake Huron), Green Bay (Lake Michigan) and southeastern Lake Superior continue to be ice-covered. Ice also remains in eastern Lake Erie, over northeastern Lake Michigan, and in parts of Lake Huron. Lake Ontario and Lake St. Clair are ice-free.

Taking a closer look at Lake Superior (above), it is interesting to compare the previous daytime VIIRS DNB image (at 19:23 UTC on 15 April) with the subsequent nighttime DNB image about 17 hours later (at 07:40 UTC on 16 April):

(1)  You can ascertain changes in the ice motion and areal coverage, even at night

(2) The later 16 April image showed that far northern portions of the Lake Superior ice had become snow-covered (exhibiting a brighter white appearance), after a weak disturbance brought small bands of lake-effect snow over that area (GOES-13 10.7 µm IR image animation). Even though the MODIS Sea Surface Temperature product showed that SST values over the open waters of northern Lake Superior were only in the low 30’s F, surface reports on the GOES-13 IR image animation indicated that the air moving across those waters in the wake of the weak disturbance was significantly colder. This fresh snow cover could have an impact on the ice melting rate in those areas.

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A Total Lunar Eclipse occurred over North America early in the morning of 15 April 2014. The resultant lack of lunar illumination had a profound impact on the “visible image at night” quality of the VIIRS 0.7 µm Day/Night Band imagery during the Suomi NPP satellite overpass at around 0800 UTC over the midsection of the United States. The animation above shows excellent illumination from the Full Moon at 0619 UTC (2:19 AM Eastern time) along the East Coast, and also at 0940 UTC (2:40 AM Pacific time) along the West Coast; however, the image at 0800 UTC (3:00 AM Central time), in the middle of eclipse totality, resembles Day/Night Band images seen during a New Moon. The three images can also be combined into a collage, as shown below, to illustrate the changes in the Day/Night band that occur as lunar intensity changes.

A comparison of three similar Day/Night Band images from the day before is here.

Even though the 08:00 UTC VIIRS Day/Night Band image exhibited a comparatively dull and “washed-out” appearance (due to very little illumination from eclipsed moonlight), there were still features of interest that could be seen. For example, a closer look over the southeastern US using the 0.7 µm Day/Night Band and 11.45 µm IR channel images (below) showed the effect of lightning activity associated with a pre-cold-frontal squall line over the Florida panhandle and the adjacent offshore waters of the Gulf of Mexico: a pair of long, narrow bright streaks (caused by cloud illumination from intense lightning activity as the sensor was rapidly scanning from northwest to southeast), abruptly followed by dark black streaks that eventually faded away. These dark black streaks represent post-saturation “recovery periods” after the sensor scanned the extremely bright cloud features. Incidentally, the coldest 11.45 µm IR brightness temperature over the Florida panhandle was -80º C (very near the area of dense cloud-to-ground lightning strikes).

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Strong winds helped a wildfire to spread very quickly through a portion of the city of Valparaíso, Chile — this fire forced large-scale evacuations, destroyed around 2000 homes, and was responsible for 12 fatalities. McIDAS images of 4-km resolution GOES-13 3.9 µm shortwave IR channel data (above) showed the fire “hot spot” (black to red color enhancement), which began late in the day on 12 April 2014, and burned through the night and into the day on 13 April. The hottest 3.9 µm IR brightness temperatures were 339.6 K (66.45º C) at 20:45 UTC and 340.8 K (67.65º C) at 23:45 UTC on 12 April.

Since the GOES-13 satellite only performs one full-disk scan (hence imaging the Southern Hemisphere) every 3 hours, the temporal behavior of this fire cannot be well ascertained. The ABI instrument on the future GOES-R satellite will perform a full-disk scan every 5 minutes.

Comparisons of 1-km resolution GOES-13 visible channel images and 4-km resolution GOES-13 3.9 µm shortwave IR images (below) showed that the narrow fire smoke plume spread rapidly to the northwest.

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A 375-meter resolution Suomi NPP VIIRS 3.74 µm (Band I4) shortwave IR image at 05:41 UTC (above) showed greater detail of the wildfire hot spot, which exhibited a maximum IR brightness temperature of 367.0 K (93.85º C). 367 K is actually the saturation temperature for the VIIRS Band I4 detectors, indicating that this was a very hot fire. Valparaiso is located about 112 km or 70 miles west-northwest of Santiago, Chile (station identifier SCEL).

By comparison, the 4-km resolution GOES-13 3.9 µm shortwave IR image close to that time (below) indicated that the maximum IR brightness temperature of the wildfire hot spot was only 316.5 K (43.35º C).

McIDAS-V images of VIIRS 3.9 µm (Band M15) shortwave IR and 0.7 µm Day/Night Band (DNB) data (below; courtesy of William Straka, CIMSS/SSEC) revealed that the large fire hot spot (yellow to red color enhancement on the shortwave IR image) was adjacent to and encroaching upon the bright night-time city lights of the Valparaiso area (as seen on the Day/Night Band image). In addition, ample illumination from a nearly-full Moon allowed the smoke plume to be seen on the DNB image, as it drifted northwestward over the adjacent waters of the Pacific Ocean.

Fires had been burning in parts of Chile since January 2014. Additional information on this Valparaíso fire can be found on the Wildfire Today site.

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Numerous grassland fires began to burn across parts of eastern Kansas (and also extreme northeastern Oklahoma) during the afternoon hours on 11 April 2014. AWIPS images of 4-km resolution GOES-13 3.9 µm shortwave IR channel data (above; click image to play animation) showed that many of these fires continued to burn into the overnight hours — the largest and most intense fire “hot spot” (black to yellow to red color enhancment) was seen northwest of Emporia, Kansas (station identifier KEMP) at 06:40 UTC or 1:40 AM local time, which exhibited an IR brightness temperature of 40º C. Smoke from these fires reduced the surface visibility as low as 2 miles at Manhattan (KMHK) and 4 miles at Topeka (KTOP). However, as high cirrus clouds began to move over the region later in the night and toward dawn, identification of the fire hot spots on GOES imagery became more difficult.

A comparison of 1-km resolution Suomi NPP VIIRS 3.74 µm and 4-km resolution GOES-13 3.9 µm shortwave IR images just after 07 UTC or 2 AM local time (below) demonstrated the advantage of higher spatial resolution for detecting not only the locations of many of the smaller fire hot spots, but also for providing a more accurate value of the intensity of the larger, hotter fires; in this case, the highest IR brightness temperature of the larger fire northwest of Emporia on the VIIRS image was 50.5º C (red color enhancement), compared to only 22.5º C (darker black color enhancement) on the GOES-13 image.

Since these fires were burning at night, they also exhibited bright signatures on the 0.7 µm Suomi NPP VIIRS Day/Night Band (DNB) image; lights from cities and towns also appeared as bright spots on the DNB image, but a comparison with the corresponding VIIRS 3.74 µm shortwave IR image helped to identify which could be attributed to actively burning fires (below).

As mentioned above, high cirrus clouds moving over the region later in the night made fire hot spot identification more difficult on the 4-km resolution GOES-13 shortwave IR imagery. However, a 1-km resolution POES AVHRR 3.74 µm shortwave IR image at 11:50 UTC or 6:50 AM local time (below) was able to detect a number of fire hot spots (darker black pixels) through the cirrus cloud features.

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