Remote Sensing of Wildfires
Remote sensing instruments, specifically satellite and radar, provide
imagery which can be quite useful for fire detection. Smoke plumes from fires can be
viewed with weather surveillance radars and visible channel satellite imagery
while the shortwave infrared (3.9 micron) satellite channel can literally sense
heat associated with fires.
The sensitivity of the WSR-88D radar and the Terminal Doppler Weather Radar (TDWR)
with its enhanced resolution allows forecasters to view
non precipitation echoes such as ground clutter, birds, insects, and smoke plumes.
On the evening of March 23, both the
KRAX WSR-88D located near Clayton, NC and the
TRDU TDWR located at the Raleigh-Durham International Airport, showed
the smoke plume over northeast Raleigh.
The animation to the right shows the base reflectivity product
from the Raleigh, Terminal Doppler Weather Radar (TDWR) from 2323 UTC on March 23
through 0017 UTC on March 24, 2010. Note the smoke plume that develops
to the northeast of Raleigh and then spreads southeasterly in the
northwesterly low level flow. The smoke plume is observed on this
radar for a little more then a half hour. A
Java Loop of
base reflectivity imagery from 2323 UTC on March 23 through 0017 UTC on March 24, 2010
that can be stopped, controlled and zoomed is available. This is one
of the first significant fires to be observed with TDWR data from TRDU.
Meteorologists often use long wave (10.7 micron) infrared satellite imagery in
weather forecasting. But the properties of the 3.9 micron channel, however, make it valuable for
detecting hot spots associated with fires. Blackbody radiance in the 3.9
micron channel increases more rapidly with temperature than the radiance
in the 10.7 micron channel. Therefore, the 3.9 micron channel is more
sensitive to sub pixel hot spots than the 10.7 micron channel, and is
resultantly better suited for fire detection. More information on
using 3.9 micron channel imagery for fire detection is available at the
and Mesoscale Meteorology Branch (RAMMB) 3.9 micron Channel Tutorial.
The image to the right is the 3.9 micron channel satellite imagery
from 2345Z (745 PM EDT) over Wake County North Carolina. The fire was first reported
around 2320Z (720 PM EDT) and the satellite image is believed to correspond to the
approximate time in which the fire was most intense; this was the best
3.9 micron channel image of the event. The one dark pixel that can
be seen in the imagery is associated with the fire on Armadale Lane. The image
indicates a pixel temperature of 14 deg C or more.
There are a few limitations to using the 3.9 micron channel to
detect sub pixel hot spots, they include:
The 3.9 micron imagery can not see through most clouds
Warm ground conditions can saturate the 3.9 micron sensor, making it impossible to discriminate fires that may be contained within the area