GOES-16 ABI RGB product artifacts related to Keep Out Zones

April 6th, 2018 |

GOES-16 ABI Full Disk Imagery at 0430 UTC on 6 April. Bands 8 (6.19 µm), 10 (7.34 µm), 12 (9.6 µm) and 13 (10.3 µm) are shown (Click to enlarge)

GOES-16 ABI Full Disk Imagery at 0530 UTC on 6 April. Bands 8 (6.19 µm), 10 (7.34 µm), 12 (9.6 µm) and 13 (10.3 µm) are shown (Click to enlarge)

Eclipse season for GOES-16 occurs around the Equinoxes when the satellite can enters the Earth’s shadow. Long ago (before GOES-12), Eclipse Season meant the satellite lost power because the solar array that powers the satellite was in a shadow. GOES-16 has batteries that allow it to function when solar power is missing. However, as the satellite emerges from the Earth’s shadow, the Advanced Baseline Imager can point too close to the Sun, so portions of the image are not scanned and sent to the receiving station. The two animations above step through four different channels on ABI (Band 8 (6.19 µm), Band 10 (7.34 µm), Band 12 (9.6 µm) and Band 13 (10.3 µm), at 0430 UTC, when the Keep-Out Zone (KOZ, sometimes called the Cookie Monster effect) is northwest of the subsatellite point, and at 0530 UTC, (also Band 8 (6.19 µm), Band 10 (7.34 µm), Band 12 (9.6 µm) and Band 13 (10.3 µm)) when the KOZ is northeast of the subsatellite point.  Note in particular that the size of the KOZ is different with different channels.

If Channel Differences are used in a product, this intra-band size difference of the KOZ has an affect.  The toggle below shows the Airmass RGB (Red Component:  Split Water Vapor (6.19 µm – 7.34 µm) ; Green Component: Split Ozone, (9.6 µm – 10.3 µm); Blue Component: 6.19 µm) at 0430 UTC and 0530 UTC on 6 April 2018.  At 0430 UTC, there is a region where only the blue part of the Airmass RGB (from the 6.19 µm band) is present;  at 0530 UTC, the Keep-Out Zone border shows only magenta (i.e., a lack of Green) because the Split Ozone Channel (9.6 µm – 10.3 µm) is missing there.

AIrMass RGB (defined in Text) at 0430 and 0530 UTC on 6 April 2018 (Click to enlarge)

NOAA’s Office of Satellite and Product Operations (OSPO) maintains a website that describes Eclipses and Keep Out Zones.

Surface Cold Front over the High Plains of Texas

April 3rd, 2018 |

Hourly GOES-16 ABI Low-Level Water Vapor Infrared (7.34 µm) Imagery, and hourly observations, 0700-1600 UTC on 3 April 2018 (Click to enlarge)

A cold front moving southward along the western Great Plains showed a distinct signature in GOES-16 Water Vapor Imagery.  The hourly animation above, with surface observations, shows the front in the Low-Level Water Vapor passing over stations where winds shift from westerly and southwesterly to strong northerly.  The feature is far more trackable in GOES-16 ABI Imagery with a 5-minute cadence as is typical over CONUS, as shown below for both low-level water vapor infrared imagery (Band 10, 7.34 µm) and upper-level water vapor infrared imagery (Band 8, 6.19 µm). The infrared imagery allowed a precise determination of when the cold front would reach a location. (In fact, because a GOES-16 Mesoscale Sector was placed over west Texas, the time of arrival could be observed down to the minute, as shown in this animation of the clean window (10.3 µm) infrared imagery from GOES-16).

GOES-16 ABI Low-Level Water Vapor Infrared Imagery (7.34 µm), 0832-1637 UTC on 3 April 2018 (Click to animate)

GOES-16 ABI Upper-Level Water Vapor Infrared Imagery (6.19 µm), 0832-1637 UTC on 3 April 2018 (Click to animate)

Visible Imagery after sunrise (below) shows that some surface cloudiness was associated with this feature — but other parts were clear.

GOES-16 ABI “Red” Visible Imagery (0.64 µm), 1252-1637 UTC on 3 April 2018 (Click to animate)

It is not common for surface features to appear in the Upper-Level Water Vapor Imagery, even when the surface is near 900 mb, as over the High Plains of west Texas. Weighting Functions show from which layers in the atmosphere energy detected by the satellite originates. The Weighting function from Amarillo TX at 1200 UTC on 3 April is shown below.  The low-level water vapor weighting function — shown in magenta — shows contributions from the surface, but the upper-level water vapor weighting function — shown in green, shows contributions ending about 200 mb above the surface, at around 700 mb.  A conclusion might be that the depth of the cold air quickly increases to around 200 mb behind the front.  Thus is can appear in the Upper-Level water vapor imagery.   The cold front passes Amarillo (here is a meteorogram) shortly before 1200 UTC (and before the Radiosonde was launched).  The radiosonde from Dodge City Kansas, however, at 1200 UTC, shows a cold layer about 200 mb thick.  (Here is the Amarillo Sounding for the same time;  it’s shown in the Weighting Function plot below as well).

Clear-Sky Weighting Functions from Amarillo TX, 1200 UTC on 3 April 2018 (Click to enlarge)

Interpretation of water vapor imagery is simplified if you use information from weighting functions to understand the three-dimensional aspect of the water vapor imagery.

Super Typhoon Jelawat

March 30th, 2018 |

Himawari-8 “Red” Visible (0.64 µm) Imagery, hourly from 2200 UTC 29 March through 0800 UTC 30 March (Click to animate)

Super Typhoon Jelawat has developed in the central Pacific Ocean, to the west of Guam and the Marianas Islands. The hourly imagery, above, from Himawari-8, from 2200 UTC on 29 March through 0800 UTC on 30 March show a rapid eye development. Satellite presentation seems best at around 0500 UTC, with a well-defined eye. Subsequently, high clouds covered the eye as it became less symmetric.

Himarwari-8 AHI Band 13 (“Clean Window”, 10.41 µm) Infrared Imagery, 2300 UTC on 29 March 2018 through 0140 UTC on 30 March 2018 (Click to enlarge)

Infrared Imagery (10.41 µm) imagery, above, shows a well-defined eye shortly after 0000 UTC. Following a data outage, imagery from 1400 UTC to 1600 UTC, below, shows a central region of cold convective clouds, but no obvious eye.

Himarwari-8 AHI Band 13 (“Clean Window”, 10.41 µm) Infrared Imagery, 1420 UTC on 30 March 2018 through 1600 UTC on 30 March 2018 (Click to enlarge)

Water Vapor Infrared Imagery from Himawari, below, shows that outflow from Jelawat is well-established to the north; outflow appears to be entrained into the mid-latitude westerlies. MIMIC Total Precipitable Water for the 24 hours ending 1600 UTC on 30 March (shown underneath the water vapor infrared imagery below) also shows the entrainment of tropical moisture around Jelawat into mid-latitudes.  The Total Precipitable Water shows a band of rich moisture extending to the east-southeast of Jelawat, portending a wet period for the Marianas Islands.

Himawari-8 AHI Water Vapor Imagery, Bands 8 (6.24 µm) and 10 (7.35 µm) at 1600 UTC on 30 March 2018 (Click to enlarge)

Morphed Microwave Observations of Total Precipitable Water, 1700 UTC on 29 March 2018 to 1600 UTC on 30 March 2018 (Click to enlarge)

Morphed Storm-centered Microwave Imagery for the 24 hours ending at 0900 UTC on 30 March, 2018 (from this site), show the rapid intensification after 0000 UTC on 30 March.  (Update:  a similar animation that ends at 1900 UTC on 30 March 2018 demonstrates a rapid collapse of the eyewall convection!)

Morphed Microwave Imagery for the 24 hours ending at ~0900 UTC on 30 March 2018 (Click to enlarge)

Full-resolution Visible Imagery from AHI (Band 3, 0.64) is shown below. (Faster and slower animations are available). A rapid organization and clearing of the eye is apparent around 0400 UTC with an equally-rapid apparent subsequent obscuration.

Full-Resolution Himawari-8 “Red” Visible (0.64 µm) Imagery, hourly from 0000 UTC 30 March through 0850 UTC 30 March (Click to animate)

GCOM overflew the storm at around 1610 UTC on 30 March, and the toggle below shows the 36.5 and 89.0 Ghz imagery over the storm (the same enhancement is used in each image).  The 36.5 Ghz imagery suggests a very asymmetric storm.  Eyewall convection in the 89 Ghz imagery is not robust. (These data were downloaded at the Direct Broadcast antenna on Guam and are courtesy Kathy Strabala, SSEC/CIMSS)

GCOM AMSR-2 36.5 and 89.0 GHz imagery over Jelawat, 1604 UTC on 30 March 2018 (Click to enlarge)

NOAA-20 and Suomi NPP also both overflew Jelawat around 1600 UTC on 30 March. The toggles below show NOAA-20 and then Suomi NPP Day Night Band visible imagery. and Infrared 11.45 Imagery, at 1549 and 1639 UTC. (Imagery courtesy William Straka, SSEC/CIMSS)  In contrast to the Visible and Infrared imagery from Himawari earlier in the day (at top), an eye is not present.  (Note that NOAA-20 data are provisional, non-operational, and undergoing testing still.)

VIIRS Infrared Imagery (11.45 µm) from NOAA-20 (1549 UTC) and Suomi NPP (1639 UTC) on 30 March 2018 (Click to enlarge)

VIIRS Day Night Band Visible Imagery (0.70 µm) from NOAA-20 (1549 UTC) and Suomi NPP (1639 UTC) on 30 March 2018 (Click to enlarge)

Suomi NPP also overflew the storm on 29 March 2018, at 0421 UTC. This was before Jelawat’s rapid intensification. The toggle below again uses data from the Direct Broadcast antenna on Guam and shows VIIRS visible (0.64 µm) and infrared (11.45 µm) imagery, MIRS products (Total Precipitable Water and Rain Rate) derived from data from the ATMS microwave sounder on Suomi NPP, and individual microwave channels from ATMS: 31, 88, 165 and 183 Ghz.

Suomi NPP VIIRS Visible (0.64 µm) and Infrared (11.45 µm) Imagery, MIRS Total Precipitable Water and Rain Rate, and individual Suomi NPP ATMS Channels: 31, 88, 165 and 183 GHz, all at 0421 UTC on 29 March 2018 (Click to enlarge)

Interests in the Marianas Islands should closely monitor the progress and evolution of this storm. This site and this site both have information on the system.

The March of Cyclones in a ‘Foureaster’ Animation

March 27th, 2018 |

GOES-16 ABI Imagery from 28 February through 24 March 2018 at 15-minute time steps. CIMSS Natural Color imagery is shown during the day, a blend of GOES-16 ABI Shortwave (3.9 µm) and Longwave (10.3 µm) Infrared imagery is shown at night. (Click to open YouTube animation)

Four weeks of GOES-16 Full-Disk imagery, spanning 28 February to 24 March at a 15-minute interval, showing four Nor’easters, are available via the image above at YouTube.  The imagery shows CIMSS Natural Color during the day and a blend of GOES-16 ABI Shortwave (3.9 µm) and Longwave (10.3 µm) Infrared imagery at night.

The original mp4 (200 megabytes) is available for download here.