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)

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

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)

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

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

Dust residue on a vehicle after the snow had melted

Ship tracks in the Atlantic Ocean

April 13th, 2013 |
GOES-13 0.63 µm visible (left) and 3.9 µm shortwave IR (right) images (click image to play animation)

GOES-13 0.63 µm visible (left) and 3.9 µm shortwave IR (right) images (click image to play animation)

A comparison of McIDAS images of 1-km resolution GOES-13 0.63 µm visible channel with the corresponding 4-km resolution 3.9 µm shortwave IR channel data (above; click image to play animation) revealed a number of ship tracks in the marine boundary layer stratocumulus cloud deck over the western Atlantic Ocean on 13 April 2013. Aerosols from the exhaust of ships causes a “cloud seeding effect”, which results in a higher concentration of smaller cloud droplets compared to the surrounding undisturbed cloud deck. These smaller cloud droplets are more effective reflectors of sunlight, resulting in a warmer (darker gray) signature on the 3.9 µm shortwave IR imagery.

A more detailed view of the ship tracks was provided using AWIPS images of 1-km resolution MODIS 0.65 µm visible channel, 3.7 µm shortwave IR channel, and 11.0 µm longwave IR channel images (below). Note that the ship track features could not be identified on the 11.0 µm longwave IR (or “IR window”) image.

MODIS 0.65 µm visible channel, 3.7 µm shortwave IR channel, and 11.0 µm longwave IR channel images

MODIS 0.65 µm visible channel, 3.7 µm shortwave IR channel, and 11.0 µm longwave IR channel images

Record snowfall in Rapid City, South Dakota

April 10th, 2013 |
GOES-13 6.5 µm water vapor channel images (click image to play animation)

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

A late-season winter storm brought heavy snowfall to much of the central US — Rapid City, South Dakota (station identifier RAP) set records that included 20.0 inches on 09 April 2013 (most snowfall on a calendar day) and 28.2 inches on 08 April10 April (greatest muti-day snowfall). McIDAS images of 4-km resolution GOES-13 6.5 µm water vapor channel data covering the 08 April – 10 April period (above; click image to play animation; also available as a QuickTime movie) showed the development of several convective elements that helped to enhance snowfall rates as they moved northward across the region on 09 April, as well deformation bands that formed as the circulation of the upper-level low slowly migrated over western South Dakota and western Nebraska on 10 April.

An AWIPS image of 1-km resolution MODIS 0.65 µm visible channel data (below) showed some of the convective elements responsible for producing a period of heavy snow at Rapid City on 09 April. Large thunderstorms were also seen at the time over notheastern Nebraska and southeastern South Dakota.

MODIS 0.65 µm visible channel image

MODIS 0.65 µm visible channel image

A surface meteorogram (below) shows the conditions at Rapid City Regional Airport during the 08-10 April period.

Surface meteorogram for Rapid City Regional Airport

Surface meteorogram for Rapid City Regional Airport

===== 12 April Update =====

Widespread cloudiness masked a good view of the areal extent of the resulting snow cover across South Dakota, but farther to the south over Nebraska and far northern Kansas an AWIPS comparison of 1-km resolution Suomi NPP VIIRS 0.64 µm visible channel and false-color Red/Green/Blue (RGB) images (below) showed interesting detail in a number of mesoscale bands of snow cover. Snow appears as white on the visible image, and as darker shades of red on the RGB image; supercooled water droplet clouds are lighter shades of white, while ice crystal clouds appear as shades of pink on the false-color image.

Suomi NPP VIIRS 0.64 µm visible channel and false-color Red/Green/Blue image

Suomi NPP VIIRS 0.64 µm visible channel and false-color Red/Green/Blue image

Ice and cloud streets in the Bering Sea

April 8th, 2013 |
Suomi NPP VIIRS 0.64 µm visible channel and false-color Red/Green/Blue (RGB) image

Suomi NPP VIIRS 0.64 µm visible channel and false-color Red/Green/Blue (RGB) image

A comparison of AWIPS images of Suomi NPP VIIRS 0.64 µm visible channel and false-color Red/Green/Blue (RGB) images (above) showed the extent of ice in the Bering Sea (snow and ice appear as shades of red in the RGB image), along with curved bands of cloud streets due to cold air advection as arctic high pressure moved toward the area from Siberia on 08 April 2013.

Consecutive VIIRS 0.64 µm visible channel images from 22:39 on 07 April and 00:21 UTC on 08 April (below) showed the amount of sea ice motion in the short time span (less than 2 hours) between the 2 images.

Suomi NPP VIIRS 0.64 µm visible channel images

Suomi NPP VIIRS 0.64 µm visible channel images