GOES-15 Super Rapid Scan Operations (SRSO) imagery

May 19th, 2013 |
GOES-15 (left) SRSO visible images and GOES-13 (right) RSO visible images (click image to play animation)

GOES-15 (left) SRSO visible images and GOES-13 (right) RSO visible images (click image to play animation)

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).

POES AVHRR 12.0 µm IR, Suomi NPP VIIRS 11.45 µm IR, and MODIS 11.0 µm IR images

POES AVHRR 12.0 µm IR, Suomi NPP VIIRS 11.45 µm IR, and MODIS 11.0 µm IR images

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.

Suomi NPP VIIRS 11.45 µm IR and GOES-13 10.7 µm IR images

Suomi NPP VIIRS 11.45 µm IR and GOES-13 10.7 µm IR images

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.

GOES-15 (left) SRSO visible and GOES-13 (right) RSO visible images (click image to play animation)

GOES-15 (left) SRSO visible and GOES-13 (right) RSO visible images (click image to play animation)

GOES-13 (GOES-East) Scanning Strategies

May 17th, 2013 |
GOES-East "Routine" scan sectors (covering a 6-hour period from 17:45 to 23:45 UTC)

GOES-East “Routine” scan sectors (covering a 6-hour period from 17:45 to 23:45 UTC)

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.

GOES-East "Rapid Scan Operations (RSO)" scan sectors (covering a 6-hour period from 17:45 to 23:45 UTC)

GOES-East “Rapid Scan Operations (RSO)” scan sectors (covering a 6-hour period from 17:45 to 23:45 UTC)

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).

List of the attributes associated with GOES imager Routine, RSO, SRSO, SRSOR and the GOES-R ABI schedules. Sample scenes are shown at the bottom.

List of the attributes associated with GOES imager Routine, RSO, SRSO, SRSOR and the GOES-R ABI schedules. Sample scenes are shown at the bottom.

Mount Pavlof erupts in the Aleutians

May 16th, 2013 |
MODIS 11.0 µm IR Window channel brightness temperature

MODIS 11.0 µm IR Window channel brightness temperature

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.

Suomi NPP VIIRS 0.7 µm Day/Night Band and 3.74 µm shortwave IR images

Suomi NPP VIIRS 0.7 µm Day/Night Band and 3.74 µm shortwave IR images

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.

Volcanic plume characteristics derived from Aqua MODIS at 13:50 UTC

Volcanic plume characteristics derived from Aqua MODIS at 13:50 UTC

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.

Volcanic plume characteristics derived from Terra MODIS at 21:31 UTC

Volcanic plume characteristics derived from Terra MODIS at 21:31 UTC

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.

Suomi NPP VIIRS 0.64 µm visible channel and 3.74 µm shortwave IR channel images

Suomi NPP VIIRS 0.64 µm visible channel and 3.74 µm shortwave IR channel images

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.

GOES-15 0.63 µm visible channel images (click image to play animation)

GOES-15 0.63 µm visible channel images (click image to play animation)

Tornado outbreak in the Dallas/Ft. Worth area in north Texas

May 15th, 2013 |
GOES-15 (left) and GOES-13 (right) 0.63 µm visible channel images (click image to play animation)

GOES-15 (left) and GOES-13 (right) 0.63 µm visible channel images (click image to play animation)

An outbreak of tornadoes across the Dallas/Ft. Worth area in north Texas on 15 May 2013 produced up to 16 tornadoes (NWS summary) which were responsible for 6 fatalities. Hail as large as 4.0 inches in diameter and a wind gust as high as 80 mph also accompanied these severe thunderstorms (SPC storm reports). A McIDAS image comparison of GOES-15 (GOES-West) and GOES-13 (GOES-East) 0.63 µm visible channel data (above; click image to play animation)  showed the rapid development of convection across the north Texas region, with the storms exhibiting a number of overshooting tops. The locations of Granbury (G) and Cleburne (C) were noted on the images, where EF-4 and EF-3 tornado damage occurred.

A similar comparison of GOES-15 (GOES-West) and GOES-13 (GOES-East) 10.7 µm IR channel images (below; click image to play animation) showed the cold cloud top IR brightness temperatures associated with these storms, which were as cold as -63 C (darker red color enhancement) in the vicinity of Granbury and Cleburne around the time of the tornadoes.

GOES-15 (left) and GOES-13 (right) 10.7 µm IR channel images (click image to play animation)

GOES-15 (left) and GOES-13 (right) 10.7 µm IR channel images (click image to play animation)

 

GOES-13 sounder Lifted Index derived product images (click image to play animation)

GOES-13 sounder Lifted Index derived product images (click image to play animation)

These storms developed along an axis of instability and moisture that was located to the east of a dryline that was bulging eastward across north Texas — the GOES-13 sounder Lifted Index (LI) derived product images (above; click image to play animation) revealed LI values as low as -12.4 C (dark purple color enhancement) at 23:00 UTC, and the GOES-13 sounder Total Precipitable Water (TPW) derived product images (below; click image to play animation) showed that TPW values were as high as 46.7 mm or 1.84 inches (darker red color enhancement) at 22:00 UTC. METAR surface reports are plotted on the sounder images (Granbury is station identifier KGDJ, and Cleburne is station identifier KCPT).

GOES-13 sounder Total Precipitable Water derived product images (click image to play animation)

GOES-13 sounder Total Precipitable Water derived product images (click image to play animation)