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

250-m resolution MODIS true color image

Moderate to extreme drought conditions across much of North Dakota during the Spring and Summer of 2008 had caused the water levels at Long Lake (a small  alkaline lake located east-southeast  of Bismarck) to become very low — as a result, bright white “salt flats” began to grow in size, becoming large enough to be seen on 1-km resolution GOES-12 visible imagery as well as on 250-meter resolution MODIS true color imagery from the SSEC MODIS Today site (above) on 18 August 2008. This feature could also be seen on MODIS true color imagery from the previous day (below, viewed using Google Earth).

MODIS true color image (viewed using Google Earth)

AWIPS images of the MODIS visible channel, Land Surface Temperature (LST) product, and Normalized Difference Vegetation Index (NDVI) product from 17 August (below) revealed that LST values were significantly cooler over the high albedo areas of the white “salt flats” (in the upper 70s to low 80s F, compared to 100-110 F over the surrounding areas), and NDVI values were very low over the dry lake bed (less than 0.1, compared to 0.4 to 0.6 in the surrounding areas).

AWIPS images of MODIS visible, LST, and NDVI (Animated GIF)

** 20 AUGUST UPDATE **

Strong southerly winds on 20 August (gusting to 40 mph at Mobridge SD, 44 mph at Jamestown ND, and 36 mph at Bismarck ND) were creating a plume of “blowing dust” off the dry lake bed of Long Lake. A comparison of GOES-12 and GOES-13 Rapid Scan Operations (RSO) visible imagery at 5-10 minute intervals (below) shows the extent of the plume. This image comparison also serves to highlight the improved navigation on the newer GOES-13 satellite — note the excellent image-to-image navigation on the GOES-13 images on the right, compared to the notable wobble on the GOES-12 images on the left.

GOES-12 + GOES-13 RSO visible images (Animated GIF)

MODIS true color imagery (below, viewed using Google Earth) showed that the plume extended northward  to the Turtle Mountain plateau (the darker green feature) along the North Dakota/Canada border! A forecaster from Rapid City SD spoke to his nephew via telephone, who was driving an agricultural combine harvester south of Martin and west of Harvey in central North Dakota — this location appeared to be right in the middle of the plume — and the nephew reported 2-3 miles visibility, but no apparent smell or odor. 

MODIS true color image (viewed using Google Earth)

Hat-tip to Lee Czepyha, Meagan Holm, and Matthew Bunkers of the National Weather Service forecast office at Rapid City, SD for first noting this interesting feature and bringing it to our attention (and getting ground truth reports)!