GOES-17 Loop Heat Pipe Anomaly Impacts Update

August 4, 2020

2 minute read

What is happening to Band 9?

Over the next few days, users of GOES-17 imagery from ABI Band 9 (Mid-level Water Vapor IR) will begin to notice the degradation of the imagery as a result of the seasonal loop heat pipe anomaly. A visual representation of the anticipated daily impacts for Band 9 can be found here and in Figure 1, below. A yellow cell with a "1" indicates estimated minimal to moderate degradation in the imagery for a given hour on a given day. Similarly, a red cell with a "2" indicates estimated severe degradation to the point that the imagery becomes unusable. The hour of day is at the top along the horizontal axis in UTC. The date is to the left along the vertical axis in ascending order.

Figure 1:  Anticipated impacts for Band 9 from July 24 - September 7

In Figure 1, above, the horizontal axis ranging from 0 to 23 (top) is the hour of the day in UTC
and the vertical axis is the calendar date from July 24 to September 7, 2020 in ascending order.​

 

Operational Impacts from Band 9 Degradation

Band 9 (6.95 µm) is the "Mid-level Water Vapor IR" band on the ABI. The "water vapor" bands are IR bands that sense the mean temperature of a variable-depth layer of moisture. For some tropical air masses, Band 9 may sense temperatures characteristic of the environment at pressures lower than 500 hPA (e.g. higher heights). In other dry or cold atmospheres, the satellite may sense at pressures higher than 500 hPa (e.g. lower heights), but surface features are not usually apparent in this band. It has many of the same applications as the other two water vapor bands. The impact of the loop heat pipe anomaly degradation to this band includes decreased ability to identify mountain waves, which may be more evident in this band than in the other two water vapor bands. More information on Band 9 can be found in this quick guide from CIMSS and this article published in the Journal of Operational Meteorology.

 

Impacted Data Products

The table below includes the GOES-17 data products that will be impacted by the degradation of Band 9. A quick guide for each data product is linked in the right column.

Data Product Link to Quick Guide
Clear Sky Mask CIMSS Quick Guide for Clear Sky Mask
Derived Motion Winds CIMSS Quick Guide for Derived Motion Winds
Derived Stability Indices CIMSS Quick Guide for Derived Stability Indices
Legacy Vertical Moisture and Temperature Profiles CIRA Quick Guide for Legacy Vertical Profiles
Total Precipitable Water CIRA Quick Guide for Total Precipitable Water
Sulfur Dioxide (SO2) RGB CIRA Quick Guide for SO2 RGB
Split Water Vapor Brightness Temperature Difference CIMSS Quick Guide for Split Water Vapor Difference

 

Supplemental GOES-15 Operations

From August 9 at 0000 UTC through September 3 at 1600 UTC, NESDIS will return the GOES-15 imager to temporary service for additional support purposes for Eastern Pacific tropical cyclones by providing imager only coverage. The GOES-15 operating position will be at 128 degrees west. GOES-17 will continue operating in the GOES-West role at 137.2 degrees with all instruments operating nominally. GOES-15 will be running a routine west schedule. For AWIPS users, GOES-15 imagery bands will once again update under the main Satellite Menu (e.g. IR Window, Water Vapor, Visible, 3.9u). Read the full message on the upcoming supplemental GOES-15 operations from the Office of Satellite and Product Operations (OSPO) here.

 

More Information on the Loop Heat Pipe Anomaly

For additional information regarding this seasonal loop heat pipe anomaly event, including the upcoming GOES-17 Mode 3 cooling timeline operations, refer to the article linked here. Mark your calendars for August 20th when Dave Pogorzala from the GOES-R Program will be presenting in the Satellite Book Club on the loop heat pipe anomaly. Stay tuned for more details on that session!