Australian Wildfires
Nighttime visible imagery (i.e. Near-Constant Contrast or NCC) clearly shows the Australian wildfires that are raging and ablaze in New South Wales, a state in southeastern Australia. NCC detects emitted lights from the fires, and at times shows the fire perimeter lines and reflected light from the extensive smoke plumes. The animation below displays nightly Suomi-National Polar-orbiting Partnership (SNPP) NCC imagery between 13-15Z from 11-13 November 2019. Cloud cover and emitted city lights from Sydney and Brisbane can also be seen. The moon phase and moon elevation angle are depicted in the bottom-left corner. The full moon phase of the lunar cycle and positive moon elevation angle imply the moon was above the horizon and provided adequate moonlight to illuminate atmospheric features (i.e. an ideal time to view NCC).
The smoke from the fires can be accentuated further utilizing an NCC enhancement technique. The AWIPS NCC color table scale can be customized to bring out certain atmospheric features in the imagery. In the images below, the default NCC 0-1 enhancement is compared to the NCC 0-0.5 enhancement on 12 November 2019. Notice how the NCC 0-0.5 enhancement brings out the smoke from the fires along with nearby cloud cover, but increases the saturation of city lights in comparison to the NCC 0-1 enhancement. For interested users, this quick guide provides steps on how to apply different enhancements to NCC imagery.
But how can one differentiate between emitted lights from fires to the emitted city lights? Users can overlay NCC with VIIRS infrared 3.74µm to identify fire hotspots at 375-m spatial resolution. NCC and VIIRS IR imagery are observed at ~1430Z, 13 November 2019 below. Hotspots (i.e. high brightness temperatures) and outlines of fire perimeters coincide with certain emitted lights. The emitted lights from cities disappear when compared to the thermal infrared.
To get an idea of the atmospheric instability near the fires users can display NUCAPS soundings; polar-orbiting satellite derived soundings that are optimal in clear-sky environments, and where in-situ observations are poor or limited. The NUCAPS sounding that is picked for this event is circled in blue (see below), observed right over one of the fires. It shows a moderately unstable, dry environment conducive for fire initiation and fire spread, where precipitable water values (derived from the sounding) are 0.31 inches. Note NUCAPS soundings are overlaid onto NCC imagery on 14 November 2019. NCC imagery observes smoke advection towards the coastline.
Downwind of the fire, another NUCAPS sounding is observed near the coastline (see blue circle). NUCAPS depicts a shallow inversion indicating a stable environment. Sounding is predominately dry, albeit there is slightly more moisture observed near the surface; increased precipitable water values (i.e. 0.55 inches) could be due to maritime influences and/or ‘fire produced water vapor advection’ towards the coastline.
