Lightning was the cause of a wildfire in southeastern Montana (about 45 miles east-southeast of Miles City) during the afternoon hours on 22 August 2008, which burned a total of about 2600 acres. AWIPS images of the MODIS 3.7 Âµm and GOES 3.9 Âµm shortwave IR channels (above) showed a significantly warmer “fire hot spot” on the MODIS 18:20 UTC image (51.0Âº C, orange pixels) compared to the 18:25 GOES image (36.5Âº C, dark black pixels). The fire hot spot on GOES imagery did not approach the temperatures seen on the MODIS image until about 20:15 UTC.
This wildfire could be viewed using GOES-11 (GOES-West), GOES-12 (GOES-East), and GOES-13 (undergoing a period of operational testing as “GOES-Central”) — you can see that there was a slight amount of image “wobble”Â on the GOES-11 and GOES-12 shortwave IR and visible images, while the corresponding GOES-13 image navigation was very steady (below). Changes to the GOES-13 spacecraft have resulted in improved image navigation compared to the previous GOES satellites.
Also note that the smoke plume on the visible images was much more apparent on the GOES-12 and GOES-13 images — this is due to the fact that the forward scattering angle was more favorable from the viewing perspectives of GOES-12 (positioned at 35Âº W longitude) and GOES-13 (positioned at 105Âº W longitude) during the late afternoon hours, which helped to highlight the smoke plume as it drifted southeastward.
A plot of the GOES-11, GOES-12, and GOES-13 3.9 Âµm shortwave IR brightness temperature values (below) showed a fair amount of variability between the maximum “fire hot spot” temperatures sensed by the different satellites. Although there was general agreement in the trend of increasing temperatures as the wildfire continued to burn, at times the measured IR temperatures differed by as much as 20Âº K (for example, at 19:45 UTC).Â The different satellite viewing angle was a contributing factor to some of these differences — at times the fire was partially obscured by cloudiness that was moving through the region during that period.