CIMSS Satellite Blog

GOES-11 + GOES-13 visible images

A comparison of GOES-11 and GOES-13 visible images (above) showed that some smoke aloft (from wildfires that had been burning in parts of the northern Rocky Mountains) was drifting over the Foothills region of eastern Colorado during the morning hours on 28 August 2008. Northwesterly winds aloft were  blowing a good deal of the smoke toward the southeast, but some smoke at lower levels could be seen moving southwestward and backing up against the higher terrain (a result of  upslope winds in the wake of a cold frontal passage  on the previous day). Both the Denver, Colorado rawinsonde report and the Platteville, Colorado NOAA wind profiler data indicated the northeasterly upslope flow was restricted to the lowest 1 km or so of the atmosphere.

A similar comparison of GOES-12 and GOES-13 images during the afternoon hours (below) showed that  the low-level smoke was still backed up against the Foothills, but was also beginning to slowly drift toward the north as the boundary layer winds began to acquire more of a southerly component. Note that the surface features on the GOES-13 animations exhibit less image-to-image movement compared to both GOES-11 and GOES-12 — improvements to the GOES-13 spacecraft Image Navigation and Registration (INR) system  include the use of star trackers to provide more precise image navigation.

data

GOES-12 + GOES-13 visible images

The smoke was easier to identify using 250-m resolution MODIS true color imagery from the SSEC MODIS Today site (below), and this smoke was also evident on the MODIS Aerosol Optical Depth product.

MODIS true color image

The Denver National Weather Service forecast discussion mentioned the smoke:

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER CO
315 PM MDT THU AUG 28 2008

.AVIATION…VFR CONDITIONS TO CONTINUE THROUGH TONIGHT. SMOKE OVER AREA HAS BEEN CREATING SOME SLANT VISIBILITY PROBLEMS UPON APPROACH AS WELL AS TAKE OFFS…BUT NO CONCERNS WITH SURFACE VISIBILITY. IT DOESN`T APPEAR THAT SURFACE VISIBILITY WILL BE REDUCED.

While there were a couple of pilot reports of haze aloft over the region around 18:00 UTC, at altitudes of 11,500  and 14,000 feet (below), the surface visibilities only dropped to 6 miles at Boulder (KBJC) and 7 miles at Denver (KDEN)  during the afternoon hours, and remained around 10 miles at other surrounding airports.

AWIPS images of the MODIS visible channel

GOES-12 and GOES-13 visible images (Animated GIF)

A comparison of GOES-12 and GOES-13 visible images centered near Rolla (station identifier KVIH) in southern Missouri (above) showed that widespread river valley fog was dissipating during the morning hours on 27 August 2008. Note the improvement in image-to-image navigation on the GOES-13 data (less “wobble” of the images), due to changes in the spacecraft design on the newer GOES-13 satellite.

A comparison of GOES-11 and GOES-13 water vapor channel images (below) demonstrates the improved detection of mesoscale mountain waves over far southwestern Alberta and northwestern Montana on that same day. The spatial resolution of the GOES-13 water vapor channel is 4 km, compared to 8 km on the older GOES-11 satellite.

GOES-11 and GOES-13 water vapor images (Animated GIF)

Mountain waves seen on water vapor imagery have long been recognized as an indicator of potential clear air turbulence. There was one pilot report (PIREP) of light to moderate turbulence at an altitude of 32,000 feet near Great Falls, Montana around 17:40 UTC (below).

AWIPS image of GOES water vapor image + PIREP

AWIPS images of MODIS and GOES shortwave IR channels (Animated GIF)

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 µm and GOES 3.9 µm shortwave IR channels (above) showed a significantly warmer “fire hot spot” on the MODIS 18:20 UTC image (51.0º C, orange pixels) compared to the 18:25 GOES image (36.5º 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”  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 35º W longitude) and GOES-13 (positioned at 105º W longitude) during the late afternoon hours, which helped to highlight the smoke plume as it drifted southeastward.

GOES-11 + GOES-12 + GOES-13 shortwave IR and visible images (Animated GIF)

A plot of the GOES-11, GOES-12, and GOES-13 3.9 µm 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 20º K (for example, at 19:45 UTC).  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.

GOES-11 / GOES-12 / GOES-13 3.9 µm IR brightness temperatures