Satellite Operations Updates - Total Operational Weather Readiness - Satellites (TOWR-S)
Loop Heat Pipe Anomaly Impacts on GOES-17 ABI Bands 13 & 14
August 26, 2020
2 minute read
What is happening to ABI Band 13?
Users of GOES-17 imagery from ABI Band 13 (Clean Longwave Window IR) should 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 13 can be found here and in Figure 1, below. A "1" in a cell indicates some degree of degradation in the imagery for a given hour on a given day. 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 13 from July 24 - September 7
and the vertical axis is the calendar date from July 24 to September 7, 2020 in ascending order.
Operational Impacts from Band 13 Degradation
Band 13 (10.3 µm) is the "Clean Longwave Window IR" band on the ABI. This band is the least sensitive to water vapor absorption compared to the other IR window bands. This results in improved atmospheric moisture corrections, identification and classification of clouds and other features, and cloud top temperature and cloud particle size estimates. Band 13 supports many baseline GOES products, such as Derived Stability Indices and Total Precipitable Water, and RGBs including Day Cloud Phase Distinction, Day Convection, and Simple Water Vapor. One impact of the loop heat pipe anomaly degradation when using Band 13 includes a decreased ability to track convective features during the day/night transition. More information on Band 13 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 13. A quick guide for each data product is linked in the right column.
What is happening to ABI Band 14?
Users of GOES-17 imagery from ABI Band 14 (Longwave Window IR) should 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 14 can be found here and in Figure 2, below. A "1" in a cell indicates some degree of degradation in the imagery for a given hour on a given day. 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 2: Anticipated impacts for Band 14 from July 24 - September 7
and the vertical axis is the calendar date from July 24 to September 7, 2020 in ascending order.
Operational Impacts from Band 14 Degradation
Band 14 (11.2 µm) is the traditional "Longwave Window IR" band on the ABI. There is more absorption of energy by water vapor at this wavelength versus Band 13. Brightness temperatures in Band 14 will therefore be cooler than those in Band 13 by an amount that is a function of the amount of moisture in the atmosphere. Band 14 plays a prominent role in many baseline GOES products, such as Fire Detection and Derived Motion Winds, as well as an ingredient to the Ash and Dust RGBs. One impact of the loop heat pipe anomaly degradation when using Band 14 includes a decreased ability to delineate storm-top signatures such as overshooting tops. More information on Band 14 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 14. A quick guide for each data product is linked in the right column.