VIIRS « CIMSS Satellite Blog

Residual winter ice in Lake Superior and Chequamegon Bay

April 27th, 2022 | Scott Bachmeier

Landsat-8 False Color image [click to enlarge]

A 30-meter resolution Landsat-8 False Color image viewed using RealEarth (above) displayed thin filaments of ice (brighter shades of cyan) in far western Lake Superior, just off the northern coast of Wisconsin, on 27 April 2022. Chequamegon Bay in northern Wisconsin also had significant amounts of ice remaining from the winter months. Remnant snow cover (muted shades of cyan) was also apparent across much of northeastern Minnesota and parts of northern Wisconsin.

During the preceding overnight hours, a NOAA-20 VIIRS Advanced Clear-Sky Processing for Ocean (ACSPO) Sea Surface Temperature image around 0831 UTC (below) indicated that SST values were generally around 34^oF (darker blue enhancement) in the portion of the lake north of the ice filaments. Farther to the east, the West Superior Buoy 45006 was reporting a SST value of 33^oF at that time.

NOAA-20 VIIRS ACSPO Sea Surface Temperature image [click to enlarge]

GOES-16 (GOES-East) True Color RGB images displayed using CSPP GeoSphere (below) showed that (1) the thin ice filaments just off the coast of Wisconsin were moving southwestward during the day, and (2) within Chequamegon Bay, significant ice fracturing began during the afternoon hours.

GOES-16 True Color RGB images [click to play animated GIF | MP4]

This ice filament motion and ice fracturing was the result of persistent northeasterly surface winds during the day, which gusted to 29 knots at Duluth Sky Harbor Airport (below).

Plot of surface report data from Duluth Sky Harbor Airport [click to enlarge]

Posted in GOES-16, Landsat, NOAA-20, RealEarth, Red-Green-Blue (RGB) images, VIIRS | Comments Off on Residual winter ice in Lake Superior and Chequamegon Bay

Flooding along the Red River of the North

April 27th, 2022 | Scott Lindstrom

ABI/VIIRS Flood/Inundation Product valid 0000 UTC 26 April 2022 (Click to enlarge)

The above image (from here; other flood product are available here) shows inundation occurring around the Red River of the North on the North Dakota/Minnesota border. The image combines the excellent spatial resolution of VIIRS on NOAA-20/Suomi-NPP with the excellent temporal resolution of the GOES-16 ABI) Precipitation over the past 7 days ending at 1200 UTC, below, from this site, shows an axis of heavy (>4″!) precipitation just south of Grand Forks. Flood gauges on 27 April (here, from “River Observations” at this site), show major flooding occurring over eastern North Dakota.

7-day precipitation ending 1200 UTC on 27 April 2022 (Click to enlarge)

The toggle below compares Band 2 and Band 5 (and the Day Land Cloud RGB) on 27 April 2022 at 1646 UTC. The 1.61 µm imagery has a very dark signal over the flooded region between Oslo and Drayton — because water absorbs energy at that wavelength (that is, it doesn’t reflect much back to the satellite) — so there is excellent contrast between land and water. Snow (and cirrus clouds) also absorb energy with a wavelength of 1.61 µm, so the reflectance differences between visible/0.64 µm (very bright) and the 1.61 µm (darker) can be used to identify regions of snow on the ground (for example between McClusky and Karlsruhe at the western edge of the image; between Langdon and Petersburg over the central part of the image); features that are bright in both the 0.64 µm and 1.61 µm imagery (for example, the feature stretching east-southeastward from between McClusky and Harvey to near Pingree) are clouds. Any RGB that includes both the 1.61 µm and the 0.64 µm (or 0.87 µm) imagery will highlight snow on the ground. The Day Land Cloud, shown in the toggle below, shows cyan in regions of snow (or cirrus).

GOES-16 Band 2 (0.64 µm), Band 5 (1.61 µm) and Day Land Cloud RGB, all at 1646 UTC on 27 April 2022 (Click to enlarge)

The series of webcam images below, spanning 21-27 April (with no 23 April image), from this website, shows the changes in the river at the Sorlie Bridge in East Grand Forks.

Webcam imagery showing the Red River of the North under Sorlie Bridge in East Grand Forks, Minnesota, 21-27 April 2022 (Click to enlarge)

Posted in GOES-16, Heavy rain / flooding, VIIRS | Comments Off on Flooding along the Red River of the North

Parallax with GOES-R and VIIRS Fire Detection

April 21st, 2022 | Scott Lindstrom

GOES-17 Fire Temperature RGB (upper left) and FDCA Fire Temperature (lower left) and GOES_16 FIre Temperature RGB (upper right) and FDCA Fire Tempeerature (lower right), 1541 – 1946 UTC 20 April 2022 (Click to enlarge)

The Tunnel Fire north of Flagstaff offers an excellent example of why knowledge of Parallax with satellite features is important. In the animations above, note how the location of the warmest pixels are shifted: GOES-17 has the warmest pixels very close to US Highway 89 leading northeast away from Flagstaff; GOES-16 has the warmest pixels just to the west of that road! Which is correct?

Even with surface-based features such as fires, parallax (see other blog posts dealing with parallax here, here, here and here) is an issue with GOES imagery. (Click here to see parallax with lakes) The perceived location is shifted away from the sub-satellite point. So for this example, the true fire location might be somewhere between the satellite-indicated locations. Note also that the FDCA values from GOES-17 differ from those GOES-16; for this fire, GOES-17 values were warmer.

NOAA-20 overflew this fire at 20:50, 20:30 and 20:10 on 19, 20 and 21 April, and imagery from the NASA Worldview site is shown below (Click here for a direct link to the 20 April scene) VIIRS imagery typically has smaller parallax shifts than GOES (and in fact, as detailed here, considerable effort has gone into better georeferencing of VIIRS imagery, as discussed in this blog post and shown in this toggle), and the fire location is therefore more accurate. The 20 April view from NOAA-20 occurred shortly after the end of the animation above, and shows a fire straddling the highway.

NASA Worldview NOAA-20 True Color Imagery and Fire Hot Spots (from I04 3.74 µm data) on 19, 20 and 21 April 2022 (Click to enlarge)

Posted in Fire detection, GOES-16, GOES-17, NOAA-20, VIIRS | Comments Off on Parallax with GOES-R and VIIRS Fire Detection

Tunnel Fire in Arizona

April 20th, 2022 | Scott Bachmeier

Suomi-NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (3.74 µm) images [click to enlarge]

A toggle between Suomi-NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (3.74 µm) images at 0954 UTC or 3:54 am local time (above) displayed the nighttime glow and thermal signatures of actively-burning portions of the Tunnel Fire on 20 April 2022. As noted in the Inciweb report, a 10-mile section of the north-south U.S. Highway 89 was closed (from milepost 425 to 435) as the fire crossed that road.

After sunrise, GOES-17 (GOES-West) Fire Temperature RGB, Shortwave Infrared (3.9 µm), Fire Power and Fire Temperature images (below) showed how the fire intensified during the day (the Fire Temperature and Fire Power derived products are components of the GOES Fire Detection and Characterization Algorithm FDCA).

GOES-17 Fire Temperature RGB (top left), Shortwave Infrared (3.9 µm, top right), Fire Power (bottom left) and Fire Temperature (bottom right) [click to play animated GIF | MP4]

A longer animation of GOES-17 Fire Temperature RGB images created using Geo2Grid is shown below. The less-intense signature of the Crooks Fire is also apparent, to the southwest of the more prominent Tunnel Fire.