GOES-17 Data Fusion: An example, and where to find the data

February 15th, 2019 |

GOES-17 Water Vapor Imagery. 6.19 µm (top row), 6.95 µm (middle row), 7.34 µm (bottom row); Left Columm:  Imagery from the ABI; Right Column:  Data Fusion Imagery created using the GOES-17 ABI Band 13 (10.3 µm) Imagery. Animation from 0902 UTC – 1727 UTC. Data Fusion imagery is not computed for the first or last images. Click to play mp4 animation.

The GOES-17 Loop Heat Pipe issue means that certain infrared bands lose data integrity at certain times, times that vary over the course of the year. Late February is a time of year when the impacts on data are very noticeable (This figure — from this blog post — shows other times of the year when the issue is most noticeable).  The Data Fusion process that uses GOES-17 ABI Band 13 imagery (relatively unaffected by the LHP issues) can create approximations of the missing imagery.  This allows for qualitative views of those missing bands.

The animation above (click here for an animated gif) shows GOES-17 Water Vapor Channels on the left (6.19 µm, 6.95 µm and 7.34 µm) and GOES-17 Data Fusion images on the right. At the beginning of the animation (0902 UTC), Data Fusion is not implemented; it uses information at 0902 to create subsequent imagery, however. In the first few frames of the animation, the impact of the LHP warming are not apparent. By 1007 UTC, however, the GOES-17 Water Vapor Bands are becoming noticeably warmer than the Data Fusion imagery. (An initial signal that LHP issues are starting is a general warming in the imagery). Data dropouts start at 1102 UTC, first at 7.34 µm, then at 6.95 µm and finally at 6.19 µm. By 1202 UTC, data integrity is lost completely, but Data Fusion maintains a signal that allows a user to qualitatively track features in the image. Shortly after 1500 UTC, data starts to reappear, initially mostly at 6.19 µm, then 6.95 µm and finally at 7.34 µm. By 1632 UTC, the PACUS (Pacific/CONUS) image shows data, but it is cooler than the Fused data (Note the cooler cloud top temperatures in all three water vapor bands).

Warmth going into LHP Data Drop-outs and coolness coming out of LHP Data Drop-outs have been documented in this directory tree that compares GOES17 and GOES16 imagery in a region in between the two satellites (a region with similar view angles). The figure below (from here, accessible from this website) shows that GOES-17 brightness temperatures (in red) are warmer than GOES-16 (in blue) before data loss, and cooler than GOES-16 immediately subsequent to data loss.

GOES-17 (red) and GOES-16 (blue) brightness temperatures for an small domain midway between the two sub-satellite points. The GOES-17 6.19 Image at 1552 UTC is also shown (Click to enlarge).

Fusion Data (in the form of netCDF files written comforming to mission standards; the netCDF files are readable by SIFT and McIDAS-V, for example) are available via ADDE from the SSEC Data Center. Send an email here for more information. Imagery is also available at the SSEC Data Center via the geo browser.

Data Fusion to mitigate Loop Heat Pipe data dropouts with GOES-17

February 13th, 2019 |

GOES-17 Band 10 (7.34 µm) imagery, 0900-1700 UTC on 13 February 2018 (Click to animate)

(The Experimental GOES-17 Data Fusion link is here).

GOES-17 is now operational as GOES-West at 137.2º W Longitude, as noted here and elsewhere. However, Loop Heat Pipe (LHP) problems persist (as noted here and here and here), with the effect varying seasonally. Because of the Loop Heat Pipe malfunction, the Advanced Baseline Imager warms up, emitting radiation at wavelengths similar to those being sensed from the Earth. This does not happen during the day when the ABI instrument is pointing towards the Earth and the Sun is behind the satellite. During the night, however, the sun illuminates the ABI instrument and warms it. This effect is most noticeable (and detrimental to the imagery) around the solstices. The animation above shows the effects of the Loop Heat Pipe on Band 10, the low-level water vapor imagery. Starting at about 1015 UTC, there is a perceptible warming of the image, globally, shortly after that the image integrity is lost and the data become unuseable. At 1615-1630 UTC, the instrumentation cools enough to produce, again, useable imagery.

The chart below shows how the temperature of the focal plane in the ABI changes throughout the course of the year. The differences between Northern Hemisphere Vernal and Autumnal Equinoxes occur because the Earth is closer to the Sun at the Northern Hemisphere Vernal Equinox. The chart also shows the effects of ‘Eclipse’ — when the satellite moves through the Earth’s shadow. When the ABI is in the Earth’s shadow, it is not being heated by the Sun (and that’s why the GOES-R Series carries batteries to power the satellite at that time). The reduced heating occurs between 26 February and 14 April in the Spring, and between 30 August and 16 October in the Fall. The chart also contains for the longwave infrared bands the temperature at which the heat from the satellite increases the likelihood of bad data.

Warmest Focal Plane Temperature as a function of Year. Also included: the threshold temperatures when the ABI Detection is affected by the warmer Focal Plane. The step in values near both Equinoxes occurs when a Yaw Flip is performed on the satellite (Click to enlarge)

Note in the plot above that Band 13 and Band 14, the clean window and longwave infrared window bands at 10.3 µm and 11.2 µm, respectively, is relatively unaffected by warming. This 10.3 µm animation (spanning the same times as the animation above) shows subtle features that are related to warming because of the faulty Loop Heat Pipe, but overall, data integrity is preserved.

The GOES-17-only fusion solution for mitigating data outages uses GOES-17 ABI Clean Window (10.3 µm) radiances to create missing spectral band radiances. In this method, the last full set of calibrated radiances at time t0 is marked (For GOES-17 at present this is done at 0900 UTC). Then, for subsequent times when LHP issues cause missing data, a so-called k-d tree search (discussed in this paper: Weisz, E., B. A. Baum, and W. P. Menzel, 2017: Construction of high spatial resolution narrowband infrared radiances from satellite-based imager and sounder data fusion. J. Appl. Remote Sens. 11 (3), 036022, doi: 10.1117/1.JRS.11.036022) is performed on time t0 infrared window band 13 measurements to find the five t0 pixels that best match each time t infrared window band 13 pixel; the five k-d tree time t0 matches for each pixel are then averaged for all ABI IR spectral bands to estimate ABI bands at time t for that pixel.

In other words, the fusion method (1) finds the five best matches of time t0 Band 13 measurements for each time t Band 13 measurement and then (2) uses the average of those t0 matches for each missing spectral band to create a fusion estimate at time t. Using time 0900 UTC for t0, when Loop Heat Pipe issues subsequently impact data quality, the Band 13 image at that time is used to predict what the other bands would look like — based on the relationship established for Band 13 measurements between time t and time t0 at 0900 UTC. The fusion method is most challenging for the Band 10 imagery — because it is the least correlated with Band 13 (especially in regions of clear skies). In contrast, a window channel like Band 11 is highly correlated with Band 13 and the Data Fusion product has few artifacts. This animation compares Band 13 and Band 11 — very similar! — and Band 13 and Band 10 — not that similar, except in regions of clouds.

A resultant image is shown below. The left-most image is the unusable GOES-17 Band 10 image. The middle image shows the GOES-17 water vapor image produced via data fusion; the right-most image is the corresponding GOES-16 Band 10 image over the same region (a region that is midway between the two satellite nadirs so that view angle differences are minimized). There are some subtle differences; in particular the Fusion product shows values that are cooler than GOES-16 in some regions, but the qualitative aspects of the match are good.

(The GOES-17 Imagery below pre-dates the 1800 UTC 12 February 2019 time when GOES-17 became operational and should therefore be considered preliminary and non-operational)

GOES-17, GOES-17 Data Fusion, and GOES-16 Low-Level Water Vapor (Band 10, 7.3 µm) Imagery, 1300 – 1445 UTC on 4 February 2019 (Click to play mp4 animation)

Data Fusion Imagery is available at the SSEC Geo Browser (Link).  It is a separate drop-down menu (‘GOES-17 Fusion’) and should be considered experimental.  The animation below shows the transition between non-fusion and fusion data.  Here is a full-disk animation from 13 February (1200 UTC to 1700 UTC) that shows Fusion Data transitioning back to GOES-17 data as the Loop Heat Pipe issues end in the morning.

GOES-17 Low-Level water vapor imagery (7.3 µm) at 1100, 1115 and 1130 UTC. Data Fusion was used to produce the 1130 UTC image (Click to enlarge)

GOES-17 becomes the operational GOES-West satellite

February 12th, 2019 |

GOES-17 Full Disk

GOES-17 Full Disk “Red” Visible (0.64 µm) images [click to play animation | MP4]

GOES-17 Mid-level Water Vapor (6.9 µm) images [click to play animation | MP4]

GOES-17 Mid-level Water Vapor (6.9 µm) images [click to play animation | MP4]

GOES-S (named GOES-17 once it reached geostationary orbit) was launched on 01 March 2018. Beginning at 1800 UTC on 12 February 2019, it became the operational GOES-West satellite (replacing GOES-15, which was launched in March 2010). The period of transition to operational status is shown on Full Disk images of “Red” Visible (0.64 µm) and Mid-level Water Vapor (6.9 µm) images (above).

In an animation of GOES-17 images from the 16 ABI spectral bands, centered on the Big Island of Hawai’i (below), an increase in cumulus clouds was evident in the Visible and Near-Infrared bands (1-6) along with a warming signature of the island summits (Mauna Kea and Mauna Loa) in the Infrared bands (7-16) as daytime heating increased during the morning hours. Weighting functions for all of the Infrared bands which are not strongly affected by water vapor absorption (7, and 11-16) have peaks at/near the surface — and the presence of dry air within the middle troposphere shifted the three Water Vapor band (8-10) weighting functions downward to allow some of the island summit thermal signature to be sensed. This dry air aloft (and a lack of cirrus clouds over the island) also enabled the summits to be sensed by the 1.37 µm Near-Infrared “Cirrus” band (4).

GOES-17 images from the 16 ABI spectral bands, centered on the Big Island of Hawai'i [click to play animation | MP4]

GOES-17 images from the 16 ABI spectral bands, centered on the Big Island of Hawai’i [click to play animation | MP4]

A comparison of all 16 ABI bands from GOES-17 covering most of Alaska and the adjacent Bering Sea is shown below.

Image loop that cycles through all 16 ABI Bands from GOES-17, covering most of Alaska [click to play MP4 animation]

Image loop that cycles through all 16 ABI Bands from GOES-17, covering most of Alaska [click to play MP4 animation]

In the animation below (source), GOES-17 and GOES-16 (GOES-East) Longwave Infrared (11.2 µm) images have been combined and displayed in a Mollweide projection. This shows the broad area of coverage provided by the current GOES constellation, which reaches from far eastern Australia to far western Europe and Africa.

GOES-17 + GOES-16 Infrared (11.2 µm) images [click to play animation | MP4]

GOES-17 + GOES-16 Longwave Infrared (11.2 µm) images [click to play animation | MP4]

Although the GOES-17 ABI instrument experiences a nocturnal Loop Heat Pipe (LHP) cooling problem (also discussed here) — which increases around the time of the Spring and Autumn equinox —  the issue only affects the emitted Longwave Infrared spectral bands (bands 08-16), and only for periods lasting as long as a few hours (peaking daily around 1300-1330 UTC). Trends of the Focal Plane Module (FPM) temperature of the ABI instrument can be monitored at this site — and examples of Band 09 (6.9 µm Water Vapor) imagery from 11 February are shown below. Note how the images return to normal after the peak FPM temperatures cool from around 97 K to around 80 K. More information on the daily variation of FPM temperatures throughout the year is available here, here and here.

Sequence of GOES-17 Band 09 (6.9 µm Water Vapor) images during a spike in the Focal Plane Module temperature on 11 February 2019 [click to enlarge]

Sequence of GOES-17 Full Disk Band 09 (6.9 µm Water Vapor) images during a spike in the Focal Plane Module temperature on 11 February 2019 [click to enlarge]

Sequence of GOES-17 CONUS sector Band 09 (6.9 µm Water Vapor) images during a spike in the Focal Plane Module temperature on 11 February 2019 [click to enlarge]

Sequence of GOES-17 CONUS sector Band 9 (6.9 µm Water µm) images during a spike in the Focal Plane Module temperature on 11 February 2019 [click to enlarge]

The LHP cooling issue affects various ABI spectral bands to differing degrees, with the Band 14 (11.2 µm Longwave Infrared) imagery being the least impacted — this can be seen in a Full Disk animation covering the same time period (below).

Sequence of GOES-17 Full Disk Band 14 (11.2 µm Longwave Infrared) images during a spike in the Focal Plane Module temperature on 11 February 2019 [click to enlarge]

GOES-17 and GOES-15 will operate in tandem from their respective locations of 137.2º West and 128º West longitude through early July 2019 — so GOES-15 imagery can be used during times when GOES-17 is adversely affected by the LHP cooling issue.

Mode 4 Testing for both GOES-16 and GOES-17

October 1st, 2018 |

GOES-17 upper-level water vapor infrared imagery (6.19 µm) from 1425-1550 UTC on 1 October (Click to animate)

GOES-17 Data shown in this post are preliminary and non-operational.

Continuous Full Disk (Mode 4) Testing is occurring on October 1 2018.   Mode 4 is the highest data flow rate for the ABI and results in a Full Disk image every 5 minutes.  No mesoscale sectors are produced during Mode 4 operations.  Five-minute CONUS imagery can be produced by subsecting the 5-minute Full-Disk Imagery.  This testing started at 0000 UTC on 1 October and will end at 0000 UTC on 2 October.

The animation above shows GOES-17 Full-Disk imagery for the upper-level water vapor imagery (6.19 µm) with a 5-minute cadence.  The GOES-16 animation for the same time and location is below.

GOES-16 upper-level water vapor infrared imagery (6.19 µm) from 1425-1550 UTC on 1 October (Click to animate)

Careful inspection of the imagery from the two satellites might reveal differences in brightness temperatures between the two instruments. This difference is due to view-angle differences. When the satellite is scanning near the limb, computed brightness temperatures will be cooler because more information detected by the satellite comes from the upper part of the atmosphere. Compare, for example, brightness temperatures just west of former Pacific Hurricane Rosa just west of Baja California. GOES-17, at 89.5 W Longitude, sees warmer temperatures than GOES-16 at 75.2 W Longitude. GOES-16’s view is more oblique, and is through more of the colder upper atmosphere.

GOES-16 and GOES-17 upper-level water vapor infrared (6.19 µm) imagery at 1500 UTC on 1 October 2018 (Click to enlarge)

(Update: GOES-16 returned to Mode-3 scanning at 1549 UTC on 1 October. Continuous Full Disk scanning on GOES-16 lead to degradation of derived products).

Update #2: Animations of 5-minute Full Disk GOES-17 Mid-level Water Vapor (6.9 µm) and “Red” Visible (0.64 µm) images from 0000-2355 UTC on 01 October are shown below.

GOES-17 Mid-level Water Vapor (6.9 µm) images [click to play MP4 animation]

GOES-17 Mid-level Water Vapor (6.9 µm) images [click to play MP4 animation]

GOES-17

GOES-17 “Red” Visible (0.64 µm) images [click to play MP4 animation]

One interesting feature on GOES-17 Visible imagery was the east-to-west progression of sun glint off the water of the Amazon River and its tributaries, beginning near the mouth of the river in northeastern Brazil and ending in Ecuador (below).

GOES-17 "Red" Visible (0.64 µm) images [click to play MP4 animation]

GOES-17 “Red” Visible (0.64 µm) images [click to play MP4 animation]