POES AVHRR 10.8 µm “IR window” image

A pair of interesting “Figure 8” aircraft condensation trails (or “contrails”) could be seen on a 1-km resolution POES AVHRR 10.8 µm “IR window” image over eastern North Dakota on 07 March 2011 (above). The contrails appeared slightly colder (brighter white) than the surrounding snow-covered ground surfaces. These contrail patterns were presumably made by military jets conducting training exercises from nearby Grand Forks Air Force Base.

The contrail patterns were even more apparent on the corresponding POES AVHRR 3.7 µm “shortwave IR” image (below). The contrail features appeared darker on the shortwave IR image due to reflection of solar radiation off the small supercooled water droplets that comprised the cloud features — and their shadows appeared as slightly cooler (brighter white) signatures on the surface.

POES AVHRR 3.7 µm “IR window” image

On the 0.63 µm POES AVHRR visible image (below), the contrail shadows showed up very well as darker features against the bright snow-covered ground. Using an Interactive Image Fader Tool, the distance offset between the contrails themselves (darker features on the shortwave IR image) and their shadows (darker features on the visible image) was quite obvious — this distance offset was due to the fairly low sun angle at this time of the day over North Dakota in early March.

POES AVHRR 0.63 µm visible image

Tip of the hat to Gregg Gallina (NOAA/NESDIS/SAB) for bring this interesting feature to our attention!

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GOES-13 0.63 µm visible channel images (click image to play animation)

AWIPS images of 1-km resolution GOES-13 0.63 µm visible channel data (above; click image to play animation) revealed the formation of convergence bands withing a weak cyclonic circulation over western Lake Superior on 07 March 2011. These convergence bands were responsible for producing some lake-effect snowfall along the north shore of the lake, over parts extreme northeastern Minnesota — Lutsen reported 8.5 inches of snow, with 5.8 inches falling north of Grand Marais.

POES AVHRR 0.86 µm visible images

A sequence of 1-km resolution POES AVHRR 0.86 µm visible channel images (above) and the corresponding 1-km resolution POES AVHRR 12.0 µm IR images (below) showed a slightly more detailed view of the convergence bands.

POES AVHRR 12.0 µm IR images

A comparison of 1-km resolution POES AVHRR Cloud Optical Depth products at 18:41 and 19:18 UTC (below) showed that the primary convergence band along the eastern side of the cyclonic circulation feature  exhibited significantly higher cloud optical depth values (blue to cyan color enhancement).

POES AVHRR Cloud Optical Depth product images

===== 08 MARCH UPDATE =====

Another well-defined vortex was observed over northern Lake Superior on the following day. A comparison of 250-meter resolution MODIS true color and false color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (below) showed the vortex cloud feature with a very long and narrow “tail” extending southward and westward from the center of the circulation, along with a complex ice structure across the far southern portion of Lake Superior. Ice and snow cover appear as cyan-colored features on the MODIS false color image, in contrast to supercooled water droplet clouds (which appear as brighter white features).

MODIS true color and false color images

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GOES-13 0.63 µm visible images (click image to play animation)

McIDAS images of GOES-13 0.63 µm visible channel data (above; click image to play animation) showed the large smoke plume from a wildfire that forced the closure of Interstate 95 in eastern Florida on 28 February 2011. A MODIS true color Red/Green/Blue (RGB) image from the SSEC MODIS Today site (below; viewed using Google Earth) offered a closer view of the growing smoke plume at 19:14 UTC. The fire burned several structures and forced evacuations of parts of Scottsmoor, Florida.

MODIS true color Red/Green/Blue (RGB) image (viewed using Google Earth)

A sequence of AWIPS images of 1-km resolution POES AVHRR and MODIS 3.7 µm shortwave IR data (below) revealed the very large “hot spot” (black to red to yellow pixels) associated with the wildfire as it jumped eastward across Interstate 95 after about 23:00 UTC (4 pm local time).

POES AVHRR 3.7 µm and MODIS 3.7 µm shortwave IR images

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MODIS true color Red/Green/Blue (RGB) image (viewed using Google Earth)

High winds (gusting to 69 mph at Amarillo, Texas) downed power lines that ignited a number of grassland wildfires across western Texas on 27 February 2011 — according to media reports, these fires destroyed at least 60 homes, burned more than 140,000 acres, and caused an accident on Interstate 20 near Midland, Texas that killed a 5-year-old child. These high winds were also responsible for widespread areas of blowing dust, which reduced surface visibilities in a number of locations. Laredo, Texas recorded a daily high temperature of 103ºF (the first high temperature of 100º F or greater of the year in the US). A MODIS true color Red/Green/Blue (RGB) image from the SSEC MODIS Today site (above, viewed using Google Earth) showed the areas which were affected by blowing dust and smoke plumes from wildfires.

A comparison of AWIPS images of 4-km resolution GOES-13 3.9 µm shortwave IR data with the corresponding 1-km resolution MODIS 3.7 µm shortwave IR data (below) demonstrated the improved fire hot spot (red to yellow color enhancement) detection capability provided by higher spatial resolution. On the MODIS image, some of the fire pixels were so hot that they “wrapped around” on the color scale and appeared as white pixels.

MODIS 3.7 µm + GOES-13 3.9 µm shortwave IR images

An AWIPS comparison of the MODIS 0.65 µm visible channel and the corresponding MODIS 1.38 µm “cirrus detection channel” image (below) showed the utility of the near-IR cirrus detection channel for highlighting the areal coverage of the blowing dust (which showed up as the slightly brighter areas, since this MODIS channel is sensitive to any particles that are efficient scatters of light). At the time of the MODIS image, winds across this region were gusting as high as 46 knots at Pecos (station identifier KPEQ).

MODIS 0.65 µm visible image + MODIS 1.38 µm "cirrus detection" image

Farther to the north over the Texas Panhandle region, a similar comparison of the 4-km resolution GOES-13 3.9 µm shortwave IR data with the corresponding 1-km resolution MODIS 3.7 µm shortwave IR data (below) again demonstrated the improved fire hot spot (red to yellow color enhancement) detection capability provided by higher spatial resolution.

MODIS 3.7 µm + GOES-13 3.9 µm shortwave IR images

A similar AWIPS comparison of the MODIS 0.65 µm visible channel and the corresponding MODIS 1.38 µm “cirrus detection channel” image (below) again showed the utility of the near-IR cirrus detection channel for highlighting the areal coverage of the blowing dust. At the time of the MODIS image, winds across this region were gusting as high as 60 knots at Amarillo (station identifier KAMA), where surface visibility was restricted to 1.5 miles.

MODIS 0.65 µm visible image + MODIS 1.38 µm "cirrus detection" image

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