Loop Heat Pipe Anomaly Impacts on GOES-17 ABI Band 9

October 13, 2020

2 minute read

What is happening to Band 9?

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 seen 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 October 9 - November 25

 

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

 

More Information on the Fall Season 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.