Detailed Description

Color Key Case pending Case closed Case reopened QA note
Large Image
Case #:PM_NPP_VAFIP_18215   Opening date: 08/03/18   Last update: 08/03/18
Status: Note
False fire is observed outside wildfire perimeters in some cases when a super heated smoke plume can set off false fire during nighttime detection. This false fire artifact has been observed in the past, particularly at night in VNP14IMG. In these cases a hot plume is detected, which carries a signature that is easily confused with that of the 'real' fire perimeter. The tall heat plume combined with the high view angle will be projected laterally on the surface, generating a false fire artifact. The artifacts are usually observed in the nighttime data as typically these super plumes tend to be flagged as clouds in the daytime scenes which prevents this detection. Users are advised to reference the VNP14 user guide in this LINK for more details.

The first image below is an example image from the FIRMS website, which shows the NPP VIIRS active fire product reporting a fire detected on July 26th, 2018 (2018.207) over Northern California's Whiskey Bottom lake. This is the projection of the false fire that is being detected by the active fire algorithm in the presence of a hot plume at high altitude over the true fire on the ground, which could be several kilometers away from the lake. The second image is section 5, the FREQUENTLY ASKED QUESTIONS of the VNP14 user guide, which explains this fire artifact in greater detail.

FIRMS Image example of SNPP false fire plume over lake


The second example below shows USGSs GeoMAC perimeter of the California Holy fire from August 8th, 2018. Fire detected by the VIIRS AF process on NRT was acquired from the FIRMS archive for 08.08.18 and overlaid with the Holy fire perimeter. Review of the S-NPP orbit map and L2 fire data both confirmed the fire pixels are located at the edge of the swath, i.e. off nadir. This example shows spurious fire projected outside of the fire perimeter due to the combination of high altitude heat plume and high view angle.

California Holy fire perimeter and FIRMS VIIRS Active Fire NRT product 08.08.2018

Occurrence: Land SIPS AS 5000, VNP14IMG, nighttime detection
PGE: ?

Large Image