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GOES-R 8.4 um (Channel 11)

GOES-R ABI Fact Sheet Band 11 (“Cloud-Top Phase” Infrared Band)

The “need to know” Advanced Baseline Imager reference guide for the NWS forecaster

By: The Cooperative Institute for Meteorological Satellite Studies (CIMSS)

 

The 8.4 μm, or “cloud-top phase” band is used in combination with the 11.2 and 12.3 μm bands to derive cloud phase and type products. This band is similar to the “traditional” IR longwave window band, although the 8.4 μm band assists in determining the microphysical properties of clouds. Using this band produces a more accurate and consistent delineation of ice clouds from water clouds during both day and night. The same three spectral bands enable detection of volcanic dust clouds containing aerosols and sulfur dioxide. Other uses of the 8.4 μm band include thin cirrus detection in conjunction with the 11.2 μm band, better atmospheric moisture correction in relatively dry atmospheres in conjunction with the 11.2 μm band, and estimation of surface properties in conjunction with the 10.3 μm band. This band is essential for generating many products.
Source: Schmit et al., 2005 in BAMS, and the ABI Weather Event Simulator (WES) Guide by CIMSS

 

Figure 1: The Advanced Himawari Imager (AHI) 8.6 μm image for Typhoon Maysak from March 31, 2015, at 06 UTC. Credit: CIMSS and JMA

 

In a Nutshell:
GOES-R ABI Band 11 (approximately 8.4 μm central, 8.2 μm to 8.7 μm)
Similar to Suomi NPP VIIRS Band M14, MODIS Band 29, SEVIRI Band 7, AHI Band 11
Not available on current GOES sounder nor imager
Nickname:
"Cloud-top phase" infrared band
Availability:
Both day and night
Primary Purpose:
Cloud-top phase, dust, and SO2 detection
Uses Similar to:
GOES-R ABI Band 13, 14, and 15

Table 1: Overview of the 8.4 μm channel

 

Figure 2: A derived product image of cloud type as diagnosed with AHI data shows three tropical systems over the western Pacific Ocean. This example demonstrates how a derived product can be used, instead of interrogating the individual spectral bands. The image is from July 7, 2015, at approximately 2:30 UTC. A scatter plot for this case using the 8.6,  11.2, and 12.4 μm channels is shown on the second page to demonstrate how the spectral bands are used to delineate between ice and water clouds. Credit: JMA, ASPB, and CIMSS.

 

Did You Know? The first geostationary imager with a band similar to ABI Band 11 (8.4 μm) was the SEVIRI from EUMETSAT, first available in 2002. The similar SEVIRI band is centered at 8.7 μm and has been used operationally for many applications, including monitoring of dust, volcanic ash, and cloud phase. The presence of this spectral band from the geostationary Perspective helped make the case for the inclusion of this band on the GOES-R series.

 

GOES-R Baseline Product Used?
Aerosol Detection  
Aerosol Optical Depth  
Clear Sky Mask X
Cloud & Moisture Imagery x
Cloud Optical Depth  
Cloud Particle Size Distribution  
Cloud Top Phase x
Cloud Top Height  
Cloud Top Pressure  
Cloud Top Temperature  
Hurricane Intensity  
Rainfall Rate / QPE x
Legacy Vertical Moisture Profile x
Legacy Vertical Temperature Profile x
Derived Stability Indices x
Total Precipitable Water x
Downward Shortwave Radition: Surface  
Reflected Shortwave Radiation: TOA  
Derived Motion Winds x
Fire / Hot Spot Characterization  
Land Surface Temperature  
Snow Cover  
Sea Surface Temperature x
Volcanic Ash: Detection & Height x
Radiances x

Table 2: List of GOES-R baseline products that use the 8.4 μm channel

 

Ward's Words: There are four infrared window channels on the GOES-R ABI and Himawari AHI. It is Important to know the nuances of the spectral response functions for these  channels, because weak absorption of water vapor is evident to the  critical user. This band is considered a “dirty window” because water vapor absorption is more prevalent than in the traditional window region at about 11.0 μm. The practical implication of this is that the brightness temperatures of surface features are slightly cooler in the presence of near-surface deep moisture. In addition, this band is useful for sulfur dioxide detection, also decreasing brightness temperatures.
Bill “Hima-Ward-i” Ward is the ESSD Chief in NWS Pacific Region and a former Guam forecaster.

 

Figure 3: This scatterplot compares brightness temperature differences over an area of both water and ice clouds. Only ice clouds have brightness temperature differences (8.6 μm minus 11.2 μm) of more than approximately 5 K. Credit: JMA, ASPB, and CIMSS.

 

Tim's Topics: In late 1989, Steven A. Ackerman, then a researcher at CIMSS, wrote a memo to NOAA NESDIS. The purpose of the letter was to suggest “as NOAA plans the spectral band passes for its future satellite instruments...consider a channel in the 8-8.5 μm region...based on recent observational and theoretical studies...that 8 and 11 μm channels are very useful in detecting...cirrus information. Inclusion of the 8 μm channel removes the ambiguity associated with the use of the 11 and 12 μm channels alone. In addition, we have found that the combination of the 8 and 11 μm channels contain information regarding the  microphysical properties of the cloud.” The memo was written and now this band is on the ABI, along with a host of other advanced geostationary imagers.
Tim Schmit is a research meteorologist with NOAA NESDIS in Madison, Wisconsin

 

ABI Band Approximate Central Wavelength (µm) Band Nickname Type Nominal Sub Satellite Pixel Spacing (km)
11 8.4 "Cloud-top phase" band IR 2.0
13 10.3 "Clean" IR Longwave Window IR 2.0
14 11.2 IR Longwave Window IR 2.0
15 12.3 "Dirty" IR Longwave Window IR 2.0

Table 3: Comparison of GOES-R channels

 

Further reading
ABI Bands Quick Information Guides: http://www.goes-r.gov/education/ABI-bands-quick-info.html
GOES-R VolAsh fact sheet: http://www.goes-r.gov/education/docs/Factsheet-Volcanic%20Ash.pdf
ABI Weighting Function page: http://cimss.ssec.wisc.edu/goes/wf/ABI/
CIMSS Satellite Blog: http://cimss.ssec.wisc.edu/goes/blog/archives/638
EUMETSAT: http://eumetrain.org/resources.html
GOES-R COMET training: http://www.goes-r.gov/users/training/comet.html  
GOES-R acronyms: http://www.goes-r.gov/resources/acronyms.html

 

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