I wanted to point out a couple of Day-Night Band (DMB) observations from the VIIRS instrument aboard the Suomi NPP satellite since we are at full moon. Yesterday, smoke from firest could easily be seen in GOES 4-km visible imagery. However, the loss of visible at nighttime with conventional geostationary imagery makes it nearly impossible to detect smoke plumes at night. The DNB imagery, while just a snapshot from a polar orbiter, at least allows for a check of how phenomena have evolved since the loss of standard daytime visible imagery. Notice the plumes of smoke in the loop of GOES imagery below.
Image 1. GOES visible imagery and METAR observations loop 2231-0045 UTC March 26-27 2013.
A few of the smoke plumes really stand out: one in SW Arkansas at site KDEQ, one west of McComb, MS and another between Jackson and Hattiesburg, MS. Notice that the smoke plume from the fire in far SE OK was reducing visibility at KDEQ in SW Arkansas. At times, visibility was reduced to 1 3/4 SM, which is within IFR conditions. If this was a Terminal Aerodrome Forecast (TAF) site, this would cause potentially large aviation impacts and a forecaster would want to know about the evolution of the fire and smoke after sunset. Granted, while only serving as a snapshot, the DNB imagery (images 2 and 3 below) show that the fires and smoke in the region had essentially dissipated by the satellite pass at approximately 0751 UTC Mar March 27.
Image 2. VIIRS DNB Reflectance image valid 0752 UTC 27 March 2013.
Image 3. VIIRS DNB Radiance RGB product valid 0752 UTC 27 March 2013.
Now, the question might remain, did the smoke actually disappear/dissipate or are the smoke plumes simply not showing up in the imagery? It seems more likely that the smoke/fires had dissipated. Early morning daytime visible imagery just after sunrise (not shown) indicated that the fires indeed had burned out.
Now, for another type of phenomenon…snow.
During the day, clouds may linger over recent snowfall and it can be difficult for forecasters to discern the true extent of the snow. Sure, observations allow forecasters a sense of the extent of snow cover, but may not allow for a sufficient assessment of its true extent. Notice in the short loop below, the clouds moving across recent snow in sections of the Midwest.
Image 4. GOES visible image loop valid 2315 – 0015 UTC March 26-27 2013.
In the imagery above, a trained eye can differentiate snow on the ground in portions of eastern Missouri and western Illinois from cloud cover. However, forecasters and others would want to know the extent of snow cover on the ground over the area. The VIIRS DNB Radiance RGB combined with the VIIRS Nighttime Microphysics RGB later that night after clouds had cleared somewhat helped to answer that question.
Imager 5. VIIRS DNB Radiance RGB valid 0752 UTC 27 March 2013.
Image 6. VIIRS Nighttime Microphysics image valid 0752 UTC 27 March 2013.
In the DNB RGB image above (image 5), the snow field is relatively easy to see extending from eastern Missouri into western Ohio. Some clouds still obscure the view and SPoRT’s Nighttime Microphysics RGB product (image 6 above) makes it very easy to distinguish clouds from areas of snow. The low/mid clouds in the area appear as yellows/oranges, while higher, colder clouds appear as deeper magenta/reds. Toggling the two images (as shown in image 7 below) makes the ease of detecting snow vs. clouds apparent.
Image 7. Toggle of Nighttime Microphysics RGB with DNB radiance RGB, both images valid 0752 UTC March 27 2013.
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