Wildfires in southern California

By Scott Bachmeier • 5 December 2017

GOES-15 Shortwave Infrared (3.9 µm) images, with hourly surface plots [click to play MP4 animation]

GOES-15 (GOES-West) Shortwave Infrared (3.9 µm) images (above; also available as an animated GIF) showed the rapid development of wildfires driven by strong Santa Ana winds in Southern California on 05 December 2017. The fire thermal anomalies or “hot spots” are highlighted by the dark black to yellow to red pixels — the initial signature was evident on the 0230 UTC image (6:30 PM local time on 04 December), however the GOES-15 satellite was actually scanning that particular area at 0234 UTC or 6:34 PM local time. The Thomas Fire (the largest of the fires) advanced very quickly toward the southwest, nearly reaching the coast.

Nighttime image toggles between Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Day/Night Band (0.7 µm) data at 0904 UTC and 1044 UTC (below) revealed the large fire hot spots, along with the extensive smoke plume that was drifting over the adjacent nearshore waters of the Pacific Ocean. With ample illumination from the Moon (which was in the Waning Gibbous phase, at 95% of Full), the “visible image at night” capability of the VIIRS Day/Night Band — which will also be available from the recently-launched JPSS-1/NOAA-20 satellite — was clearly demonstrated.

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Day/Night Band (0.7 µm) images, with plots of surface reports [click to enlarge]

A toggle between the two VIIRS Day/Night Band images (below; courtesy of William Straka, CIMSS) showed initial darkness resulting from fire-related power outages in Santa Barbara County to the north, and Ventura County to the south (in the Oxnard/Camarillo area).

Suomi NPP VIIRS Day/Night Band (0.7 µm) images [click to enlarge]

This large wind-driven fire was also very hot — the maximum brightness temperature on the VIIRS 4.05 µm Shortwave Infrared image was 434.6 K or 322.6º F, which was above the saturation threshold of the VIIRS 3.75 µm Shortwave Infrared detectors (below).

Suomi NPP VIIRS 4.05 µm and 3.75 µm Shortwave Infrared images [click to enlarge]

In a comparison of daytime GOES-15 Visible (0.63 µm) and Shortwave Infrared (3.9 µm) images (below), the west-southwestward transport of smoke over the Pacific Ocean was clearly seen.

GOES-15 Visible (0.63 µm, top) and Shortwave Infrared (3.9 µm, bottom) images [click to play MP4 animation]

A more detailed view of the thick smoke originating from the 3 fires (from north to south: the Thomas, Rye and Creek fires) was provided by a 250-meter resolution Aqua MODIS true-color Red-Green-Blue (RGB) image from the MODIS Today site (below).

Aqua MODIS true-color RGB image [click to enlarge]

Immediately downwind of the Creek Fire, smoke was reducing the surface visibility to 1 mile at Van Nuys and adversely affecting air quality (below).

Time series plot of surface reports at Van Nuys, California [click to enlarge]

===== 06 December Update =====

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (3.75 µm and 4.05 µm) images [click to enlarge]

The fires in Southern California continued to burn into the following night, as shown by Suomi NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (3.75 µm and 4.05 µm) images (above; courtesy of William Straka, CIMSS). A large-scale view with Day/Night Band imagery revealed the extent of smoke transport westward over the Pacific Ocean.

GOES-15 Shortwave Infrared (3.9 µm) images (below) displayed the thermal signatures exhibited by the fires. Note the appearance of a new fire — the Skirball Fire — first appearing on the 1300 UTC (5:00 AM local time) image, just north of Santa Monica (KSMO). Although the Santa Ana winds were not quite as strong as the previous day, some impressive wind gusts were still reported.

GOES-15 Shortwave Infrared (3.9 µm) images, with hourly surface plots [click to play MP4 animation]

A toggle between 250-meter resolution Terra (1911 UTC) & Aqua (2047 UTC) MODIS true-color images from MODIS Today (below) showed significant pyrocumulus development from a flare-up along the northeast perimeter of the Thomas Fire. The cloud plume only exhibited a minimum infrared brightness temperature of +5.5º C on the corresponding Aqua MODIS Infrared Window image, far above the -40ºC threshold assigned to pyroCumulonimbus clouds.

Comparison of Terra (1911 UTC) & Aqua (2047 UTC) MODIS true-color RGB images [click to enlarge]

===== 07 December Update =====

Suomi NPP Day Night Band Imagery, 3-7 December 2017, over southern California

RealEarth imagery of the Day Night Band over 5 days (one image each night from 3 through 7 December), above, shows the evolution of the fire complex (Imagery courtesy Russ Dengel, SSEC). Similarly, a closer view of daily composites of VIIRS Shortwave Infrared (3.74 µm) imagery (below) revealed the growth and spread of the Thomas Fire from 04-07 December.

$Suomi NPP VIIRS Shortwave Infrared (3.74 µm) image composites [click to enlarge\$

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) image composites [click to enlarge]

In a toggle between Terra MODIS true-color and false-color RGB images (below), the large burn scar of the Thomas Fire (shades of red to brown) was very apparent on the false-color image.

Terra MODIS true-color and false-color images [click to enlarge]

Categories: Air quality, Aqua, Fire detection, GOES-15, MODIS, Red-Green-Blue (RGB) images, Suomi NPP, Terra, VIIRS

CIMSS Satellite Blog

CIMSS Satellite Blog

Wildfires in southern California