7.3 microns - Total Operational Weather Readiness - Satellites (TOWR-S)
GOES-R 7.3 um (Channel 10)
GOES-R ABI Fact Sheet Band 10 (“Lower-Level Water Vapor” 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 7.3 μm band is one of three mid-tropospheric water vapor bands on the ABI. It reveals information about lower mid-level atmospheric flow (depending on the amount of moisture in the upper troposphere) and can help identify jet streaks. It has been proven to be useful, under certain conditions, in identifying and tracking volcanic plumes due to upper-level sulfur dioxide absorption. Vertical moisture information can be gained from comparison of measurements in all three ABI water vapor bands as is done with current GOES sounder bands. This water vapor band is similar to a band on the current GOES sounders, although those bands are spectrally narrower. The heritage GOES imager water vapor band falls “between” this band and the 6.2 μm.
Source: Schmit et al., 2005 in BAMS, and the ABI Weather Event Simulator (WES) Guide by CIMSS.
Figure 1: The Advanced Himawari Imager (AHI) 7.3 μm image for Typhoon Maysak from March 31, 2015, at 06 UTC. Credit: CIMSS and JMA
|In a Nutshell:|
|GOES-R ABI Band 10 (approximately 7.3 μm central, 7.2 μm to 7.4 μm)|
|Similar to MODIS Band 28, SEVIRI Band 6, AHI Band 10|
|Available on current GOES sounder|
|"Lower-Level Water Vapor" infrared band|
|Both day and night|
|Monitor atmospheric water vapor features|
|Uses Similar to:|
|ABI/AHI Bands 8/9|
Table 1: Overview of the 7.3 μm channel
Figure 2: This image shows better evidence of an elevated mix layer in the current GOES sounder 7.4 μm band compared to the GOES imager water vapor band. The implication for convective initiation is shown in the green circles in this example from June 1, 2011, at approximately 14:00 UTC. The 7.4 μm band senses the lower-level moisture discontinuity that extends from Rochester, New York, to Indianapolis, Indiana, better than the other water vapor bands (some not shown). Credit: ASPB, CIMSS and Christopher Gitro, NWS Pleasant Hill, Missouri.
Did You Know? Significant effort is placed on ensuring the spacecraft delivers the imagery we expect without an early-life failure. There are many redundant components on the ABI and both the instrument and spacecraft are put through many tests before launch. These tests include component-level testing, instrument testing (vibration, acoustics, putting the instrument in a vacuum chamber, heating the instrument to extreme temperatures, etc.). Many of these tests are repeated after the instrument is integrated on the spacecraft, before launch. All of these tests, along with corresponding reviews, provide confidence that the ABI will work on-orbit over the long haul.
Figure 3: GOES-12 imager 4 km 6.5 μm WV band observations at 20:02 UTC on March 6, 2014, (left panel). Synthetic 2 km resolution imagery at 20:00 UTC for the GOES-R ABI WV Band 10 (7.3 μm) (right panel). The grayscale enhancement is fixed to the warmest temperature in each image and is applied over a 14 K range to make the wave features apparent in all spectral bands. Dark values are warmer values. Credit: Feltz et. al., 2009 (AMS).
|GOES-R Baseline Product||Used?|
|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|
|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|
|Sea Surface Temperature|
|Volcanic Ash: Detection & Height||x|
Table 2: List of GOES-R baseline products that use the 7.3 μm channel
Chris' Corner: With the advent of three water vapor bands on the ABI, monitoring atmospheric water vapor in the GOES-R era will be enhanced. These bands will sample upper-level, mid-level, and low-level water vapor and provide operational meteorologists the opportunity to monitor the evolution of atmospheric features in these levels. These bands will also allow for improved baseline products such as Atmospheric Motion Vectors (AMVs) that contribute to Numerical Weather Prediction models.
The arrival of the 7.3 μm band may have significant impacts on forecasting convection because atmospheric features that are difficult to analyze using the 7.0 or 6.2 μm water vapor bands may be more apparent in the 7.3 μm band. For example, the 7.3 μm band will allow forecasters to track features that have been associated with severe weather such as elevated mixed layers, elevated cold fronts, and low-level boundaries at high temporal and spatial resolution.
Christopher M. Gitro is a senior meteorologist for the National Weather Service at the field office in Pleasant Hill, Missouri.
Figure 4: Calculations demonstrate, for the clear sky, how the brightness temperatures change with atmospheric moisture for the three ABI water vapor bands. With the same temperature profile, a much colder brightness temperature is expected with more total moisture. In general, more moisture causes more cooling (as water vapor absorption occurs higher in the troposphere). Credit: ASPB and CIMSS.
Tim's Topics: When this water vapor band was first proposed on the ABI, it was to be centered at 7.4 μm. This is fine for water vapor applications, but is sub-optimal for aviation applications, such as upper-level SO2 associated with volcanoes. After working with several in the aviation community, including Gary Ellrod, then of NOAA NESDIS, the band center was moved to 7.34 μm to better capture absorption due to SO2. Thus, monitoring of some upper-level SO2 will be possible from the ABI. Knowing the location of SO2 plumes can be very important for many applications, including aviation, health, and the economy. The rapid refresh and improved spatial resolution, along with new spectral bands, will allow the ABI to better monitor aviation hazards than the heritage imager.
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)|
|8||6.2||"Upper-level water vapor" band||IR||2.0|
|9||6.9||"Mid-level water vapor" band||IR||2.0|
|10||7.3||"Low-level water vapor" band||IR||2.0|
Table 3: Comparison of GOES-R channels
ABI Bands Quick Information Guides: http://www.goes-r.gov/education/ABI-bands-quick-info.html
Real-time Weighting Function page: http://cimss.ssec.wisc.edu/goes/wf/
CIMSS Satellite Blog: http://cimss.ssec.wisc.edu/goes/blog/archives/category/himawari-8
VISIT on GOES WV: http://rammb.cira.colostate.edu/training/visit/wv_svr_wx
GOES-R SO2: http://www.goes-r.gov/products/opt2-so2-detection.html
GOES-R COMET training: http://www.goes-r.gov/users/training/comet.html
GOES-R acronyms: http://www.goes-r.gov/resources/acronyms.htm