Suomi NPP VIIRS 1.61 µm “snow/ice discrimination channel” images

A sequence of AWIPS images of Suomi NPP VIIRS 1.61 µm near-IR “snow/ice discrimination channel” data covering the period from 13:47 UTC on 27 May to 23:24 UTC on 28 May 2013 (above) showed the effects of ice jam flooding along the Yukon River in the vicinity of Galena, Alaska (station identifier PAGA). In addition to snow and ice, water is also a strong absorber at the 1.61 µm near-IR wavelength — so it appears darker on the images. This dark signature of water inundation can be seen increasing in areal coverage during that 1.5 day period. This flooding forced the evacuation of around 300 residents of Galena, as many homes were extensively damaged by the flooding.

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” images at 21:43 UTC on 28 May (below) showed that the Yukon River downstream of Galena was still snow/ice covered (appearing brighter white on the 0.64 µm and 0.86 µm images). Meanwhile, the darker signature of floodwaters near and upstream of Galena was evident to some extent on the 0.86 µm image, but was even more pronounced on the 1.61 µm image. The Yukon River ice jam flooding in the Galena area occurred about a week after similar ice jam flooding occurred much farther upstream in the Fort Yukon area.

Suomi NPP VIIRS 0.64 µm visible channel, 0.86 µm land/water discrimination channel, and 1.61 µm snow/ice discrimination channel images

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GOES-14 6.5 µm water vapor channel images (click image to play animation)

An unusual late-season nor’easter storm produced heavy rainfall (as much as 6.14 inches at Whiting, Maine) and heavy snow (as much as 13.4 inches at Mount Mansfield in Vermont and 34 inches at Whiteface Mountain, New York) during the 24 May – 26 May 2013 period. McIDAS images of GOES-14 6.5 µm water vapor channel data (above; click image to play animation) displayed some interesting storm structures during the 25-26 May timeframe.

AWIPS images of the MIMIC Total Precipitable Water product (below; click image to play animation) showed that a long atmospheric river was transporting abundant tropical moisture northward, which was then wrapping inland around the storm circulation.

MIMIC Total Precipitable Water product (click image to play animation)

A comparison of 1-km resolution Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR channel images at 05:52 UTC or 1:52 AM local time on 26 May (below) showed cloud features associated with the storm as it was centered just off the coast of Maine. Strong northerly/northwesterly winds along the back side of the storm (gusting as high as 102 mph at Mt. Washington, New Hampshire) were producing bands of orographic waves clouds over parts of Vermont and New York. This example helps to highlight the “visible image at night” capability of the VIIRS Day/Night Band (given ample illumination by moonlight).

Suomi NPP VIIRS 0.7 µm Day/Night Band abd 11.45 µm IR channel images (with overlay of surface analysis)

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CONUS view of GOES 10.7 µm Longwave Infrared (IR Window) imagery

At 10:00 UTC on 23 May, GOES-14 imagery started flowing to AWIPS as the GOES-East satellite (as seen in the comparison between the 09:30 and 10:10 UTC IR images above). Work continues on evaluating the status of GOES-13. GOES-14 remains in geostationary orbit at 105.5 West longitude, and GVAR data are being broadcast directly from GOES-14 (not relayed through GOES-13). Updates on GOES-13 — and all satellites — can be found here.

GOES sounder water vapor channel (6.5 µm) imagery from GOES-13 and GOES-14

Sounder data from GOES-14 are also flowing into AWIPS. The 6.5µm water vapor channel imagery from the GOES Sounder is much cleaner on GOES-14 than on GOES-13, as shown in the image comparison above. Note also that the Sounder footprint is slightly different between GOES-13 (positioned at 75 W) and GOES-14 (positioned at 105.5 W).

GOES-14 0.63 µm visible channel images (click image to play animation)

For the first 24 hours or so, users will notice some slight problems with the accuracy of the Image Navigation and Registration (INR), as can be seen in a sequence of GOES-14 0.63 µm visible channel images (above; click image to play animation).

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Last GOES-13 10.7 µm image before outage

GOES-13 suffered an anomaly overnight: the satellite is no longer pointed towards the Earth for as yet unknown reasons. The anomaly started at 03:40 UTC on 22 May, and at 04:29 UTC, GOES-15 (GOES-West) began a 30-minute full disk scan schedule.

Last GOES-13 10.7 µm images before outage

Successive images from just before the anomaly (above), at nominal times of 03:15 UTC and 03:32 UTC, are shown. There is a large navigation offset (~200 km) apparent in the right panel, which panel shows the last scanned image from GOES-13 before the major anomaly. The offset is also apparent in the image at the top of the page (Look, for example, at Cuba, or in the northwest corner of the image)

GOES-14, in standby mode at 105.5 W longitude, has been activated; the first images from GOES-14 will be available at 05:00 UTC 23 May. There are no plans now to move GOES-14 from its current position. In the meantime, GOES engineers are working on a solution to GOES-13’s problems. An update from the Environmental Satellite Processing Center (ESPC) is scheduled for around Noon eastern time (see NOAA NESDIS GOES Special Bulletins). Note that GOES-14 data will *not* be relayed via GOES-13 — so ground station users will need to reposition their antennas to receive GOES-14 direct readout data.

In addition, GOES-12 (GOES-South America) continues to give coverage from its position over 60 W. Full-disk imagery is available every three hours, and routine sampling (both Imager and Sounder) continues and is available here.

— Note to NWS AWIPS Users —

GOES-15 (GOES-West) full-disk coverage

With the temporary loss of GOES-13 (GOES-East), the GOES-15 (GOES-West) satellite has been placed into Full Disk scan mode, which only provides imagery over CONUS every 30 minutes — and the quality of the imagery degrades over the eastern US (above), due to the very large view angle from GOES-15 (which is located at 135 West longitude). Parallax error is also greatly increased.

During such an outage of geostationary satellite data, imagery from polar-orbiting satellite instruments (such as Terra and Aqua MODIS, Suomi NPP VIIRS, and POES AVHRR) can be used when available to help fill in temporal data gaps, and also provide a much more detailed image in terms of spatial resolution (and with a lack of a large parallax error).  The animation below covers the time period from 04:00 UTC to 11:00 UTC, showing the GOES-15 IR imagery at 30 minute intervals with the insertion of IR images from MODIS, VIIRS, and AVHRR when available. You can immediately see the value of the higher spatial resolution provided by the polar-orbiting satellite data.

Animation of GOES-15 IR images, with available polar-orbiter satellite IR images inserted

A direct comparison of GOES-15 and Suomi NPP VIIRS IR imagery around 07:00 UTC (below) again shows the better detail provided by the higher spatial resolution of VIIRS (along with a lack of parallax error) for severe thunderstorms that were producing large hail and damaging winds across parts of the lower Mississippi Valley region.

Comparison of 07:03 UTC Suomi NPP VIIRS IR image and 07:00 UTC GOES-15 IR image

In addition, the availability of a Day/Night Band on the VIIRS instrument can provide a “visible image at night”, which can be helpful for locating important  features such as convective overshooting tops and low-level cloud edges (below).

Suomi NPP VIIRS IR and Day/Night Band images

Imagery and products from AVHRR, MODIS, and VIIRS are available in AWIPS via LDM subscription.

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