Snow and ice across the Tennessee Valley and mid-Atlantic regions

January 31st, 2010
MODIS visible channel + MODIS Red/Green/Blue (RGB) false color images

MODIS visible channel + MODIS Red/Green/Blue (RGB) false color images

A large winter storm spread heavy snowfall, sleet, and freezing rain from Texas and Oklahoma to the East Coast of the US during the 28-30 January 2010 period. AWIPS images of the MODIS visible channel and a MODIS false-color Red/Green/Blue (RGB) image using the visible and the 2.1 µm near-IR “snow/ice” channels (above) showed the resulting wide swath of snow cover across the Tennessee Valley and mid-Atlantic regions on 31 January 2010. This example also offers a glimpse at the type of RGB image capability that should be available with the upcoming AWIPS II software.

Snow cover (which appears as brighter white features on the visible image) is a strong absorber at the 2.1 µm wavelength — so it appears red on the false-color RGB image. However, ice is an even stronger absorber, so areas that received a significant accrual of ice (from freezing rain, freezing drizzle, and/or sleet) appeared as an even darker red band along the southern periphery of the broad area of snow cover — this darker red band was especially evident across parts of southern Tennessee, southern North Carolina, and extreme northern South Carolina. In contrast, supercooled water droplet clouds appear as brighter features on the RGB image.

A MODIS true color image from the SSEC MODIS Today site (below; viewed using Google Earth) showed the locations of some of the heaviest snowfall amounts in each state, as well as 2 locations that received the highest accruals of ice (0.75 inch at Wallace in North Carolina, and 0.5 inch at Franklin in Tennessee).

MODIS true color image (viewed using Google Earth)

MODIS true color image (viewed using Google Earth)

Increasing ice along the western and southern nearshore waters of Lake Michigan

January 28th, 2010
MODIS visible + MODIS Red/Green/Blue (RGB) image

MODIS visible + MODIS Red/Green/Blue (RGB) image

A story on the National Weather Service Milwaukee/Sullivan website highlighted the appearance of ice on Lake Michigan on MODIS imagery on 28 January 2010. A comparison of AWIPS images of the 1-km resolution MODIS visible channel and a false color Red/Green/Blue (RGB) image (above) confirms that the brighter features seen on the visible image over the nearshore waters (from Milwaukee, Wisconsin to Chicago, Illinois to Gary, Indiana) were indeed lake ice (snow cover and ice appear as darker red features on the MODIS false color RGB image). This example offers a glimpse at the type of RGB image capability that should be available with the upcoming AWIPS II software.

A closer view using 250-meter resolution true color images from the SSEC MODIS Today site (below) revealed that the northwesterly surface winds were causing a small amount of motion of the ice field between the time of the Terra satellite overpass (17:11 UTC or 11:11 am local time) and the Aqua satellite overpass (18:54 UTC or 12:54 pm local time).

MODIS true color images

MODIS true color images

A comparison of the 18:54 UTC Aqua MODIS true color and false color images (below) again confirms that the features seen over the nearshore waters were indeed lake ice — snow cover and ice appear as cyan-colored features on this particular false color imagery.

MODIS true color and false color images

MODIS true color and false color images

Welcome back GOES-13!

January 27th, 2010
GOES-12 and GOES-13 sounder channel data

GOES-12 and GOES-13 sounder channel data

The GOES-13 satellite was brought out of on-orbit storage on 27 January 2010 — and a comparison of the 19 channels of the sounder instrument on GOES-12 and GOES-13 (above) shows an improvement in the noise characteristics that were beginning to plague the GOES-12 sounder in late 2009.

GOES-12 imager channel data

GOES-12 imager channel data

The imager instruments on GOES-12 (above) and GOES-13 (below) share the same 5 channels (1 visible and 4 InfraRed). However, the GOES-13 satellite has improved Image Navigation and Registration (INR), which eliminates a great deal of the image-to-image wobble that is often seen with GOES-12. In addition, larger batteries aboard the spacecraft allow GOES-13 to continue to operate through the Spring and Fall season “eclipse periods” (when the satellite is in the Earth’s shadow and the solar panels cannot generate the power needed to operate the various instrument packages).

GOES-13 imager channel data

GOES-13 imager channel data

GOES-13 (launched in May 2006, with a Post Launch Test conducted in December 2006) will replace GOES-12 (launched in July 2001) as the operational GOES-East satellite on 14 April 2010. At that point, GOES-12 will then be moved to a new position at 60º West Longitude to support South American operations. More information on the transition of GOES-13 into operations is available from the NOAA/NESDIS Satellite Services Division.

Snow cover across northern Arizona

January 26th, 2010
MODIS true color image (viewed using Google Earth)

MODIS true color image (viewed using Google Earth)

A series of powerful storms affected the southwestern US during the 18-23 January 2010 period, which resulted in record rainfall and snowfall in parts of northern Arizona. Flagstaff recorded 54.2 inches of snow, which was their 2nd largest storm total snowfall on record. A 250-meter resolution MODIS true color image from the SSEC MODIS Today site (above) showed the coverage of snow across the higher elevations of northern Arizona on 25 January 2010.

On the following day, a comparison of AWIPS images of the MODIS visible channel and a false-color Red/Green/Blue (RGB) image (below) shows that most of the bright features seen on the visible were snow cover (which shows up as darker pink features on the false color image).

MODIS visible image + MODIS false color RGB image

MODIS visible image + MODIS false color RGB image