Blowing dust in New Mexico and Texas

March 26th, 2010 |
GOES-12 visible images

GOES-12 visible images

McIDAS images of the GOES-12 0.65 µm visible channel data (above) showed the development of a large plume of blowing dust across parts of southern New Mexico and western Texas late in the day on 26 March 2010. Surface winds gusted to 84 mph at El Paso in Texas, with the blowing dust temporarily reducing the surface visibility to 0.1 mile.

A 250-meter resolution Aqua MODIS true color Red/Green/Blue (RGB) image from the SSEC MODIS Today site (below) revealed that at the time of the Aqua satellite overpass (20:24 UTC), plumes of blowing sand were already beginning to stream northeastward from the White Sands National Monument and Missile Range in southern New Mexico — the blowing sand had already reached the partially snow-covered Sacramento Mountains located to the east of Alamogordo. At that time, the surface visibility at Alamogordo was 5 miles…but within 3 hours the visibility there dropped to 0.5 mile.

Aqua MODIS true color image (viewed using Google Earth)

Aqua MODIS true color image (viewed using Google Earth)

With the approach of darkness, the GOES-12 (GOES East) visible channel imagery could no longer be utilized to track the location and movement of the thick airborne dust — however, the older GOES-11 (GOES West) satellite imager instrument still retains a 12.0 µm channel that is helpful for creating a simple 10.7 – 12.0 µm (channel 04 – channel 05) IR temperature difference product that is useful for tracking airborne dust (and also volcanic ash) at night. Such a sequence of GOES-11 10.7 – 12.0 µm images (below) showed that the dust plume (yellow to cyan color enhancement) continued to move eastward and northeastward across Texas and into southwestern Oklahoma during the hours after sunset.

GOES-11 10.7-12.0 µm IR temperature difference images

GOES-11 10.7-12.0 µm IR temperature difference images

A few hours later, a similar MODIS IR difference product created by subtracting the brightness temperatures of the 11.0 µm and 12.0 µm channels (below) showed that the leading edge of the dust (yellow color enhancement) had moved as far as northern Oklahoma and extreme southern Kansas. Note the “cleaner” appearance of the MODIS IR difference product, a result of the higher spatial resolution (1 km) and improved spectral response of the IR channels on the MODIS instrument compared to the GOES imager.

Aqua MODIS 11.0-12.0 µm IR temperature difference product

Aqua MODIS 11.0-12.0 µm IR temperature difference product

The ABI instrument aboard the GOES-R satellite will mark the return of the 12.0 µm channel on the GOES imager, which will allow such phenomena to be more easily identified and tracked.

Fire and Ice in northern Minnesota

March 26th, 2010 |
MODIS true color and false color images

MODIS true color and false color images

A comparison of 250-meter resolution MODIS true color and false color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (above) showed a large fire (perhaps a prescribed burn?) in a remote area of the Red Lake Indian Reservation, just to the west of the Upper and Lower Red Lakes in far northern Minnesota on 26 March 2010. On the false color RGB image, the fire hot spot shows up as a large bright red feature — note the rapid increase in areal coverage of the burn area between the time of the 17:04 UTC Terra satellite overpass and the 18:50 UTC Aqua satellite overpass. The still-frozen lakes appear as varying shades of cyan, while unfrozen bodies of water show up as a much darker blue color. On the true color RGB image, the hazy-looking smoke plume can be seen drifting northward (advected by surface winds from the south that were gusting as high as 29 knots).

MODIS 3.7 µm, POES AVHRR 3.7 µm, and GOES-12 3.9 µm shortwave IR images

MODIS 3.7 µm, POES AVHRR 3.7 µm, and GOES-12 3.9 µm shortwave IR images

AWIPS images of the 1-km resolution MODIS 3.7 µm, the 1-km resolution POES AVHRR 3.7 µm, and the 4-km resolution GOES-12 3.9 µm shortwave IR channel data (above) shows some important differences in both the location of the hottest pixels (GOES-12 has the fire located farther to the west, in far eastern Pennington county) as well as the intensity of the hot spots: the 18:42 UTC MODIS image registered a maximum IR brightness temperature value of 46.5º C, and the 18:48 UTC POES AVHRR image registered a value as high as 54.5º C. At that same time, the cursor readout for the 18:45 UTC GOES-12 image read “NO DATA” — thus demonstrating the value of the 1-km resolution MODIS and POES AVHRR imagery for identifying the exact location of the hottest portion of the fire.

An animation of the 4-km resolution GOES-12 3.9 µm shortwave IR images (below) did show that the fire hot spot was gradually growing in size, and briefly began to exhibit IR brightness temperature values as high as 37.5º C at 17:45 UTC and 48.0º C at 18:15 UTC — but then the fire intensity exceeded the AWIPS temperature threshold and “NO DATA” was indicated by the AWIPS cursor readout before the fire hot spot eventually became obscured by a dense cirrus cloud canopy drifting overhead from the southwest..

GOES-12 3.9 µm shortwave IR images

GOES-12 3.9 µm shortwave IR images

The shortwave IR channels on the ABI instrument aboard the GOES-R satellite will have a spatial resolution of 2 km, which should produce images that more closely resemble the 1-km resolution MODIS and POES AVHRR images shown above (further enhancing our fire detection capabilities in the future).