Air quality « CIMSS Satellite Blog

Blowing dust in the Four Corners region of the US

April 16th, 2013

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

Strong southwesterly winds ahead of an advancing cold front caused large areas of blowing dust across parts of the “Four Corners” region of the western US on 16 April 2013. Wind gusts were as high as 68 mph at Winslow, Arizona — and Interstate 40 was closed between Winslow and Winona, as visibility was reduced to 50 feet at times in some areas. McIDAS images of 1-km resolution GOES-13 0.63 µm visible channel data (above; click image to play animation) showed the growth of large plumes of blowing dust during the day, with primary source regions appearing in northeastern Arizona and northwestern New Mexico.

A comparison of AWIPS images of 1-km resolution MODIS 0.65 µm visible channel and 11-12 µm IR brightness temperature difference (BTD) data at 19:49 UTC (below) revealed the hazy signature (on the visible image) and large BTD values of -3 to -5 C (orange to red color enhancement) associated with the most dense plumes of blowing dust that were moving northeastward. In southwestern Colorado, surface visibility was reduced to 1 mile at Cortez (station identifier KCEZ), and winds gusted to 75 mph at Wolf Creek Pass (station identifier KCPW).

MODIS 0.65 µm visible image and 11-12 µm IR brightness temperature difference product

A 250-meter resolution MODIS true-color Red/Green/Blue (RGB) image from the SSEC MODIS Today site (below) showed the lighter tan-colored plumes of blowing dust in great detail.

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

Later in the day, there were public reports of “dirty rain” at Grand Junction, Colorado, as well as “dirty snow” in the Denver area.

Photo of dust sediment in melted snow water

In the Fort Collins, Colorado area, two photos (courtesy of Louis Grasso and Dan Bikos, CIRA) showed (1) blowing dust sediment in a container of melted snow water collected on 17 April (above), and (2) dust residue on a vehicle after the snow had melted on 18 April (below).

Dust residue on a vehicle after the snow had melted

Posted in Air quality, GOES-13, Google Earth, MODIS, Red/Green/Blue (RGB) images | No Comments »

Blowing dust in New Mexico and Texas

March 23rd, 2013

MODIS 0.65 µm visible channel and 1.375 µm nearr-IR “cirrus detection channel” images (with surface observations and frontal analysis)

Strong winds associated with a cold frontal passage created large areas of blowing dust across parts of New Mexico and Texas on 23 March 2013. The maximum wind gusts were as high as 82 mph in New Mexico and 77 mph in Texas. A comparison of AWIPS images of 1-km resolution MODIS 0.65 µm visible channel and 1.375 µm near-IR “cirrus detection channel” images (above) demonstrated the utility of the near-IR imagery for more accurately displaying the areal coverage of the airborne dust that might not be entirely apparent on the standard visible channel imagery. The strength of the 1.375 µm channel is the detection of particles that are efficient scatterers of light (such as cirrus ice crystals, volcanic ash, haze, and dust) — so in this case the dense plumes of blowing dust showed up very well, especially in comparison to the corresponding visible channel image.

For additional information and images of this event, see the NWS Lubbock TX news story and the Wide World of SPoRT blog.

Posted in Air quality, MODIS | No Comments »

Historic blizzard affects parts of Texas, Oklahoma, and Kansas

February 26th, 2013

GOES-13 6.5 µm water vapor channel images (click image to play animation)

A powerful winter storm brought historic snowfall amounts and widespread blizzard conditions to parts of Texas, Oklahoma, and Kansas during the 25 February – 26 February 2013 period (see additional information from the NWS forecast offices at Amarillo TX, Norman OK, Dodge City KS, Wichita KS, and Topeka KS). AWIPS images of 4-km resolution GOES-13 6.5 µm water vapor channel images (above; click image to play animation) showed the evolution of the storm system on 25 February, which included the development of well-defined dry slot and comma head signatures.

A comparison of 1-km resolution MODIS 0.65 µm visible channel, 11.0 µm IR channel, and 6.7 µm water vapor channel images (below) revealed a snapshot of the storm at 20:00 UTC or 3 PM local time on 25 February. A line of deep convection exhibiting cold cloud top temperatures extended from the Gulf of Mexico northward into Missouri, which produced large hail, damaging winds, and a tornado (SPC storm reports).

MODIS 0.65 µm visible, 11.0 µm IR, and 6.7 µm water vapor channel images

Very strong winds were associated with this storm, which created a large area of blowing dust across southwest Texas and southeastern New Mexico on 24 February — and GOES-13 0.63 µm visible channel images (below; click image to play animation) revealed additional areas of blowing dust across drought-stricken areas of southern Texas on 25 February, where winds gusted as high as 56 mph and visibilities were reduced to 1 mile or less in some locations (see NWS Brownsville TX summary).

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

During the following overnight hours the clouds had cleared across the Texas panhandle region, which allowed the Suomi NPP VIIRS 0.7 µm Day/Night Band (below) to provide a “visible image at night” (aided by bright illumination from the “full snow moon”) to display the areal extent of the fresh snow cover at 08:38 UTC or 3:38 AM local time. While the deep snow pack appeared somewhat colder on the corresponding VIIRS 11.45 µm IR image, the exact edges of the snow cover were easier to see on the Day/Night Band image.

Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR images

During the afternoon hours on 26 February, a comparison of the Suomi NPP VIIRS 0.64 µm visible channel image with the corresponding false-color Red/Green/Blue (RGB) image at 20:02 UTC or 3:02 PM local time (below) aided in the discrimination between snow cover (varying shades of darker red on the RGB image) and supercooled water droplet cloud features (lighter shades of white). Glaciated (ice crystal) cloud features exhibit a lighter pink appearance in the RGB image.