Working midnight shifts this past weekend, I had the opportunity to take a look at the VIIRS Day-Night Band Imagery for the detection and analysis of fog. Early Monday morning, the observation at Ft. Payne was indicating fog with 1/2 statute mile visibility. However, the presence of thin cirrus over parts of the area did not allow for the observation of ground phenomena, including fog, in the region via traditional Shortwave IR imagery (Image 1). However, low clouds and fog were observed in the VIIRS Day-Night Band imagery since the cirrus were sufficiently translucent in the visible portion of the spectrum (Image 2).
I could show the standard fog product imagery (11-3.9 µm), but the story is essentially the same as that of the 3.9 µm imagery of course. The ability to see through thin cirrus is one of the primary advantages offered by the VIIRS Day-Night Band imagery and thus is among its most useful applications, operationally speaking. These imagery are a part of the JPSS Proving Ground and have been available in AWIPS here at the HUN office for several years now, including other SPoRT collaborative partners.
In this particular case, it was operationally advantageous to see that the extent of the fog was not widespread and was just confined to some of the more fog-prone valley locations, especially the Paint Rock Valley, and may have only been highly localized to Ft. Payne, or even just the Ft Payne airport observation location. Had the fog been observed through a larger area in Jackson and especially in DeKalb Counties, then a dense fog advisory might have been necessary.