A sequence of 3 VIIRS True Color Red-Green-Blue (RGB) images from Suomi NPP and NOAA-20 as visualized using RealEarth (above) showed plumes of blowing dust moving off the coast of Namibia and South Africa on 07 August 2020.

EUMETSAT Meteosat-11 Visible (0.6 µm) images (below) displayed the motion of the dust plumes during the daytime hours.

A plot of surface data from Luderitz, Namibia (station identifier FYLZ) is shown below; it indicated that winds gusted to 36 knots (41 mph) at 08 UTC.

H/T to Santiago Gassó for bringing this event to our attention.

#sentinel2 had a not-so-centered overpass, but some of the northern plumes seem to me like sand although there are plumes coming of the pan further inland. #highlatitudedust @sheffield_dust @jobullard https://t.co/pBaIQf2Z3v pic.twitter.com/4hwnR59CNa

— Santiago Gassó (@SanGasso) August 9, 2020

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VIIRS Today, like MODIS today, subsects the US into 8 sectors of equal size. If you live in central South Carolina, or in the middle of Florida, for example, the Sector 7/Sector 8 seam is right on top of you. Perhaps you want to view the entire Great Lakes in one image, rather than a split between Sector 3 and Sector 4. (This image, from this website, shows the 8 sectors over the United States).  There are easy ways to create seam-spanning imagery.

Because the sectors are of fixed and unchanging locations and sizes (1300×1500 for 1-km resolution, 5200×6000 for 250-m resolution), it’s a simple matter to create a script to access the imagery, cut parts out, and paste them back together. For this task, I use ImageMagick, a useful, scriptable image manipulation package. The two grid sizes (950x1100 for sector USA3, 700x1100 for sector USA4) and offsets (+351+101 for sector USA3,+0+101 for sector USA4) were determined by trial and error that took about 5 minutes.

The first script below is for the 1-km resolution images. The second script below is for 250-m resolution images; it has a multiplication factor of 4 applied. These scripts are on a unix system, and it would be simple enough to put some date-enabling at the front end to make this useful in a cron. That exercise, as they say, is left to the reader.

wget http://ge.ssec.wisc.edu/viirs-today/images/noaa20/true_color/2020_08_03_216/n2.20216.USA3.143.1000m.jpg
wget http://ge.ssec.wisc.edu/viirs-today/images/noaa20/true_color/2020_08_03_216/n2.20216.USA4.143.1000m.jpg
convert -crop 950x1100+351+101 n2.20216.USA3.143.1000m.jpg test1_1000.jpg
convert -crop 700x1100+0+101 n2.20216.USA4.143.1000m.jpg test2_1000.jpg
convert test1_1000.jpg test2_1000.jpg +append n2.20216.GreatLakes.143.1000m.jpg

wget http://ge.ssec.wisc.edu/viirs-today/images/noaa20/true_color/2020_08_03_216/n2.20216.USA3.143.250m.jpg
wget http://ge.ssec.wisc.edu/viirs-today/images/noaa20/true_color/2020_08_03_216/n2.20216.USA4.143.250m.jpg
convert -crop 3800x4400+1401+401 n2.20216.USA3.143.250m.jpg test1_250.jpg
convert -crop 2800x4400+0+401 n2.20216.USA4.143.250m.jpg test2_250.jpg
convert test1_250.jpg test2_250.jpg +append n2.20216.GreatLakes.143.250m.jpg

The 1-km resolution True-Color imagery from NOAA-20 (‘n2’ in the file name; ‘n1’ is Suomi-NPP) for the Great Lakes on day 216 of the years 2020 (i.e., 3 August 2016, represented as 20216 in the url) is shown above; it spans sectors USA3 and USA4. The 250-m resolution image is here.

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From an email received from South Carolina:  Our area is always split between USA7 and USA8, making it hard to use the sectorized imagery.

A script for that region, in this case for Day Night Band imagery, is below. This script accesses both Suomi-NPP and NOAA-20 data.

wget http://ge.ssec.wisc.edu/viirs-today/images/noaa20/night_dynamic/2020_08_05_218/n2.20218.USA8.DNBD.1000m.jpg
wget http://ge.ssec.wisc.edu/viirs-today/images/noaa20/night_dynamic/2020_08_05_218/n2.20218.USA7.DNBD.1000m.jpg
convert -crop 800x750+501+0 n2.20218.USA7.DNBD.1000m.jpg test1_1000.jpg
convert -crop 800x750+0+0 n2.20218.USA8.DNBD.1000m.jpg test2_1000.jpg
convert test1_1000.jpg test2_1000.jpg +append n2.20218.SOUTHCAROLINA.DNBD.1000m.jpg
wget http://ge.ssec.wisc.edu/viirs-today/images/snpp/night_dynamic/2020_08_05_218/n1.20218.USA8.DNBD.1000m.jpg
wget http://ge.ssec.wisc.edu/viirs-today/images/snpp/night_dynamic/2020_08_05_218/n1.20218.USA7.DNBD.1000m.jpg
convert -crop 800x750+501+0 n1.20218.USA7.DNBD.1000m.jpg test1_1000.jpg
convert -crop 800x750+0+0 n1.20218.USA8.DNBD.1000m.jpg test2_1000.jpg
convert test1_1000.jpg test2_1000.jpg +append n1.20218.SOUTHCAROLINA.DNBD.1000m.jpg

The Day Night Band Composite from NOAA-20 is shown below. Click here to see the Suomi-NPP image.

This technique would work with MODIS Today imagery as well.

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A sequence of Suomi NPP VIIRS Day/Night Band (0.7 µm), Near-Infrared (1.61 µm and 2.25 µm), Shortwave Infrared (3.75 µm) and Active Fires product at 2335 UTC on 04 August 2020 (above) showed nighttime reflective and thermal signatures of the fire that was burning about 8.5 hours following a large explosion that occurred at 1508 UTC in Beirut, Lebanon.

Plots of Spectral Response Functions (SRFs) for similar spectral bands on the GOES-R series ABI instrument (1.61 µm, 2.24 µm and 3.9 µm) are shown below — note that the 1.61 µm and 2.24 µm SRF curves are located close to the peak emitted radiance of very hot features such as large fires.

EUMETSAT Meteosat-8 Visible (0.8 µm) images (below) showed a subtle signature of the explosion cloud as it slowly spread out to the northwest, west and southwest before sunset. Station identifier OLBA is Beirut  Rafic Hariri International Airport.

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CIMSS has hosted the MODIS Today website for many years.  Its follow-on, the VIIRS Today has gone live as of 4 August 2020.

As with MODIS today, the USA is subdivided into 8 sectors, and imagery on a 2-km, 1-km and 250-m grid is provided, even though VIIRS’ best resolution at nadir is 375 m (and 750 m for the Day Night Band).

The images above show True-Color and False Color imagery from Suomi NPP on shortly after noon on 3 August over the northeast United States, along with Day Night Band Imagery from NOAA-20, also from (the early morning of) 3 August, shortly before the Full Moon.

VIIRS Today does have an archive going back several years.  The website allows you to choose either Suomi-NPP or NOAA-20 data (links at the page will also show you today’s Suomi-NPP and NOAA-20 orbital passes), and you can view True Color Imagery (combining channels only in the visible part of the electromagnetic spectrum), False-Color Imagery (combining visible and near-infrared information) or (unique to VIIRS) Day Night Band Imagery.  There is also a link to a webpage showing the Moon Phase.

The image below, downloaded from VIIRS Today, shows the NOAA-20 Day Night Band composite from the morning of 4 August 2020 (link).

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