MODIS fog/stratus product and 11.0 µm IR images

Even though very cold arctic air had invaded much of the north-central US  (minimum temperatures on the morning of 15 December were -33º F at Havre, Montana and -28º F at Bottineau, North Dakota), the deeper man-made lakes (created by dams) along the Missouri River remained unfrozen on 16 December 2008. AWIPS images of the MODIS fog/stratus product and the 11.0 µm IR window (above) revealed long plumes of supercooled water droplet clouds (MODIS Cloud Phase product) streaming eastward from the relatively warm lakes — the cloud plumes were enhanced with yellow to orange colors on the fog/stratus product image, and the warm lakes were enhanced with yellow to orange colors on the IR window image.

GOES-12 10.7 µm IR images (below) showed the evolution of these “lake-effect cloud plumes” during the night-time and early morning hours on 16 December. While winds at the surface were fairly light, the winds higher aloft (at the 925 hPa or 3000 ft level) were advecting the cloud material eastward.

GOES-12 10.7 µm IR images

250-meter resolution MODIS true color and false color Red/Green/Blue (RGB) imagery from the SSEC MODIS Today site (below) showed a closer view of Fort Peck Lake in northeastern Montana and Lake Sakakawea in western North Dakota on the previous day (15 December). Small plumes of  lake-effect clouds could be seen beginning to stream southeastward off the unfrozen lakes at that time — these supercooled water droplet clouds exhibited a brighter white appearance on the false color images, in contrast to the cyan snow-covered ground.

MODIS true color and false color images (Fort Peck Lake, Montana)

MODIS true color and false color images (Lake Sakakawea, North Dakota)

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AWIPS 4-panel GOES imagery (IR, visible, water vapor channels)

The GOES-12 satellite (the operational GOES-East satellite) suffered a Thruster 2B oxidizer leak around 22:00 UTC on 14 December 2008, which caused the suspension of GOES-12 Imager and Sounder data. For several hours following the GOES-12 thruster anomaly, GOES-11 (the operational GOES-West satellite) was placed into Full-Disk mode to provide coverage as far east as possible. AWIPS 4-panel GOES images (above) show that the image quality was adversely impacted over the far eastern US and Canada during that time, due to the very large viewing angle from GOES-11 (which is positioned at 135º W longitude). Also, note that the water vapor channel imagery (lower right panel) was not available in AWIPS during the time that GOES-11 IR imagery (upper 2 panels) was filling in for the missing GOES-12 data — and of course, there was no visible channel data (lower left panel) since it was night-time.

However, the GOES-13 satellite — which had been in an extended period of on-orbit storage at 105º W longitude — had been activated in early August of 2008, so it could very quickly be utilized to replace GOES-12. As of 12:30 UTC on 15 December, GOES-13 data began to replace GOES-12 data as the GOES-East satellite data source for AWIPS, which then allowed  the image quality over the far eastern US and Canada to return to normal. The channels on the GOES-13 Imager and Sounder are identical to those on GOES-12 (including the 4-km resolution water vapor channel) — however, the primary improvements with GOES-13 are better image navigation, and larger on-board batteries to allow the satellite to operation through Spring and Fall eclipse periods (when the satellite is in the Earth’s shadow, and the solar panels cannot provide power to the spacecraft instruments).

For the latest information, see the NOAA Satellite Services Division Special Bulletins.

Note: GOES-13 data is being re-broadcast through GOES-12, so users with GOES East direct broadcast ground stations do not need to adjust their antennas.

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MODIS visible, cirrus, 3.7 µm IR, and water vapor images

Strong winds were producing plumes of blowing dust across parts of southeastern New Mexico and the  Texas panhandle region on 14 December 2008 — this blowing dust was reducing surface visibility to 1 mile at Lubbock, Texas (station identifier KLBB). AWIPS images of the MODIS visible, “cirrus detection”, 3.7 µm shortwave IR, and 6.7 µm water vapor channels (above) showed the plumes around 19:51 UTC. The plumes of airborne aerosols exhibited a lighter gray “hazy” appearance on the visible image (and to a lesser extent on the “cirrus detection” image, due to that channel’s sensitivity to particles that scatter light).

In addition, there was a small cluster of hot MODIS 3.7 µm IR pixels with a maximum temperature of 46º C located just northwest of Hobbs, New Mexico (station identifier KHOB), due to a grass fire that was burning in that area (MODIS 3.7 µm image) — and 250-meter resolution MODIS true color imagery (below) confirmed the presence of a lighter-colored smoke plume embedded within the longer orange-colored blowing dust plume. The burn scar from this fire was clearly evident on MODIS true color imagery (viewed using Google Earth) on the following day (located between Lovington and Maljamar, New Mexico).

MODIS true color image

The strong winds (which gusted as high as 71 mph at Tatum, New Mexico) were producing mountain waves immediately downwind of the higher terrain in the “Big Bend region” of Texas — a comparison of 1-km resolution MODIS 6.7 µm and 4-km resolution GOES-12 6.5 µm water vapor images (below) demonstrated the value of better spatial resolution for detecting such mesoscale phenomena.

MODIS 6.7 µm and GOES-12 6.5 µm water vapor images

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MODIS visible and "snow/ice channel" images

A major ice storm impacted much of the Northeast US on 11 December – 12 December 2008 — many locations across that region experienced several hours of freezing rain, leading to widespread ice accumulations of 0.5 to 1.0 inch which brought down tree limbs and power lines (causing power outages for an estimated 1 million customers). After the storm, AWIPS images of the MODIS visible and near-IR “snow/ice” channel from the morning of 13 December 2008 (above) offered some clues as to the areal coverage of the more significant ice accrual. Since snow and ice are strong absorbers of radiation at the near-IR 2.1 µm wavelength,  the darkest areas on the snow/ice image are areas where the thickest accrual of ice occurred (although lakes and other bodies of water also appear as dark black features). Note that some of the darker ice-covered areas on the snow/ice image do not look as “bright” on the visible image as adjacent areas with deeper snow cover, since the ice (without a layer of snow on top) is generally more “translucent” or light gray in appearance than the brighter white snow cover.

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