A comparison of AWIPS images of Suomi NPP VIIRS 1.61 µm “snow/ice discrimination channel” data from 19 May and 20 May 2013 (above) revealed the areal extent of flooding along the Yukon River upstream of the Fort Yukon (station identifier PFYU) area in northeastern Alaska. Both ice and water are strong absorbers at the 1.61 µm wavelength, so they appear very dark on the images. The flooding along the Yukon River began as a surge of ice and water moved through the Eagle, Alaska (station identifier PAEG) area on 17 May, then continued downstream to produce major flooding in the Circle, Alaska area on 19 May (Circle is located about halfway between PAEG and PFYU). An ice jam had formed about 12 miles upstream of Fort Yukon, which then impounded the flow of ice and water that had flooded Circle, leading to the increased flooding seen upstream of Fort Yukon on 20 May.

A comparison of Suomi NPP VIIRS 0.64 µm visible channel, 0.86 µm “land/water discrimination channel”, and 1.61 µm “snow/ice discrimination channel” at 20:52 UTC on 20 May (below) showed how the 0.86 µm and 1.61 µm images can be used to identify the darker flooded portions of the Yukon River that are not apparent on the 0.64 µm visible image.

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The GOES-15 (GOES-West) satellite was placed into Super Rapid Scan Operations (SRSO) on 18 May 2013 (to support the IfloodS field experiment), providing bursts of imagery at 1-minute intervals. At the same time, the GOES-13 (GOES-East) satellite had been placed into Rapid Scan Operations (RSO) due to the threat of severe weather over the central US, providing images as frequently as every 5-10 minutes. A comparison of 0.63 µm visible channel GOES-15 SRSO  images with GOES-13 RSO images covering western Kansas, western Oklahoma, and the Texas Panhandle regions (above; click image to play animation; also available as a QuickTime movie) showed interesting views of the convective storm development — both from a perspective of the different satellite viewing geometries, and also the different temporal resolution from the different scanning strategies of the two GOES satellites. One of the more notable tornadoes on this day (SPC storm reports) moved through Rozel, Kansas.

About a half hour prior  to the start of the GOES-15 SRSO period, a sequence of three AWIPS images of 1-km resolution IR data from POES AVHRR (12.0 µm), Suomi NPP VIIRS (11.45 µm), and Aqua MODIS (11.0 µm) showed the rapid cooling of cloud-top IR brightness temperatures (to values of -70 F and colder, black color enhancement), even before any cloud-to-ground lightning strikes were detected (below).

A comparison of the 19:43 UTC 1-km resolution Suomi NPP VIIRS 11.45 µm IR image with the corresponding 4.km resolution GOES-13 10.7 µm IR image (below) demonstrated the value of higher spatial resolution for the earlier and more accurate detection of the cold cloud-top IR brightness temperatures values associated with the rapidly-developing convective cells over southwestern Kansas. The actual times that the two satellite were imaging the storms were very close, yet the difference in coldest IR brightness temperature values (-58 C on GOES, compared to -77 C on VIIRS) was quite striking. The northwestward shift in the location of features on the GOES-13 image was due to parallax.

On the following day (19 May 2013), GOES-15 was again placed into SRSO mode, allowing a similar GOES-15 SRSO vs GOES-13 RSO visible image comparison of the development of severe convection over Oklahoma and Kansas (below; click image to play animation; also available as a QuickTime movie). One of the more notable tornadoes on this day (SPC storm reports) moved through Shawnee, Oklahoma, causing 2 fatalities.

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In normal or “Routine” operations, GOES Imagery (from both GOES-East and GOES-West) follows a schedule that includes scans of CONUS (Continental US) nominally every 15 minutes.

For GOES-East, these are images at :02, :15, :32 and :45 after the hour. The :02 and :32 images are CONUS only: the southern boundary is the central Caribbean Sea and the eastern boundary stretches from Newfoundland to the Windward Islands. The :15 and :45 images include the entire north Atlantic Ocean and stretch southward to 20 S latitude (these are called ‘Northern Hemisphere Extended’). Full-disk images are produced every three hours (02:45, 05:45, 08:45, 11:45, 14:45, 17:45, 20:45 and 23:45 — all times UTC). The Full-Disk image takes 26 minutes to scan and that means a CONUS scan does not occur during the Full-disk scan. In routine operations, after the CONUS scan at :02 and :32 minutes past the hour, a South American scan over Chile and Argentina occurs (starting at :09 and :39 minutes past the hour). On a ‘normal’ day, nearly 130 images are produced by the Imager of GOES-13; of these, 87 are CONUS. An example of the Routine scan sectors is shown above (also available as a QuickTime movie), and a diagram of the Routine scan sectors is also shown here.

There is also daily ‘station-keeping’ during which times (00:34-00:40 and 15:30-15:45 for GOES-13) system scheduling, diagnostics and maintenance are performed.

During GOES-East Rapid Scan Operations (RSO), scanning of the Southern Hemisphere is curtailed sharply. The Northern Hemisphere Extended imagery at :15 and :45 is replaced by images that extend only to the Equator (and take 9 minutes to scan, versus 14 for the Northern Hemisphere Extended). The only Southern Hemisphere imagery scanned — other than the full disk image every three hours — is a small segment over the tropical eastern Pacific, the Southern Hemisphere Short sector that provides information for Sea surface temperature estimates. These images are produced hourly on the half-hour and take less than two minutes to scan. RSO operations yields CONUS imagery from GOES-13 at :02, :10, :15, :25, :32, :40, :45, and :55, every hour, except when the full disks are scanned at times noted above, in which cases the :55, :02 and :10 imagery are not scanned. RSO imaging produces almost 160 images; more than 120 of those are CONUS. An example of the RSO scan sectors is shown above (also available as a QuickTime movie), and a diagram of the RSO scan sectors is shown here.

During Super Rapid Scan Operations (SRSO), southern Hemisphere scanning includes only the every-three-hour Full Disk image. Northern Hemisphere scanning continues (:15 and :45), the CONUS scans are shifted slightly (:59 and :30) and small sectors are scanned at one-minute intervals (the one-minute interval determines how many lines can be scanned). These are at :04, :05, :06, :07, :08, :09, :10 or :11, :12, :25, :35, :36, :37, :38, :39, :40, :41 or :42, :43 and :55. An example of SRSO scan sectors is shown here (QuickTime movie), and a diagram of SRSO sectors is shown here. During a few days in August-October 2012 and also in June and August 2013 GOES-14 will be performing Super Rapid Scan Operations for GOES-R Super Rapid Scan Operations for GOES-R (SRSOR) scans (SRSOR image viewer).

The link for GOES-East scheduling is here.

The table below presents the schedules for GOES-East for the different operations: Routine, Rapid-Scan Operations (RSO), Super Rapid-Scan Operations (SRSO), Experimental Super Rapid-Scan Operations for GOES-R (SRSOR), and GOES-R ABI (GOES-R is scheduled to launch in 2015).

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Pavlof Volcano (located at about 55.5 N, 162 W) in the Aleutian Islands had been experiencing a series of small eruptions that were captured by the constellation of polar-orbiting satellites that pass over the region. For example, a MODIS 11.0 µm IR Window channel image from 08:07 UTC on 16 May (above) showed a dark (warm) pixel over the volcano. That 0º C pixel was surrounded by values closer to -15º C.

A comparison of Suomi NPP VIIRS 0.7 µm Day/Night Band (DNB) and 3.74 µm shortwave IR images at 12:12 UTC on 16 May 2013 (above) showed the bright glow of the volcano on the DNB, centered over a warm thermal anomaly of 47.5º C (orange color enhancement) on the shortwave IR. These were both signatures of hot lava flows from the summit and down along the northwest flank of Pavlof.

The high spectral resolution of MODIS — 36 different channels in the visible and infrared — on board the Terra and Aqua satellites allows for creation of products that quantitatively describe the volcanic ash cloud, beyond just locating the hot spot of the volcano itself. False color imagery, shown above (top left panel, derived from the brightness temperature differences indicated in the figure) from Aqua MODIS at 13:50 UTC, nicely outlines the volcanic ash plume in shades of red. The other three figure panels show the Ash Cloud Height (very important information for aviation concerns), the Ash Cloud Particle Size (which is related to how long it will take to settle out — small particles stay in the atmosphere for a longer time) and Ash Cloud Loading (what is the mass of volcanic ash in the column?).

A later 4-panel suite of products derived from MODIS data on Terra, at 21:31 UTC, is shown below. In addition to the high spectral resolution on MODIS, the polar orbiter satellites have good horizontal resolution over Alaska as well.

A comparison of Suomi NPP VIIRS 0.64 µm visible channel and 3.74 µm shortwave IR channel images at 22:08 UTC (below) showed the hazy signature of the volcanic plume on the visible image, as well as a warm thermal anomaly exhibiting a brightness temperature of 40º C (yellow color enhancement) on the shortwave IR image. A Volcanic Ash Advisory had been issued for altitudes between the surface and 15,000 feet, as the volcanic plume drifted southeastward at 15 knots.

GOES imaging of this eruption suffers because of limited channels (5) on the GOES Imager, and because of degraded spatial resolution at the high latitudes (as result of the very large satellite viewing angle). However, the hazy signature of the volcanic plume could still be seen drifting southeastward from Pavlof on GOES-15 0.63 µm visible channel images (below; click image to play animation). The location of the Pavlof volcano is denoted by the “P” on the images. Also of interest in the animation is the motion of sea ice in the Bering Sea north of the Aleutians, which could be seen once a break in the clouds moved over that area.

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