Introduction to the GOES Sounder

In our last class we reviewed Planck's function.  

Using Maple you were able to make a series of plots which illustrate how the amount of radiant energy emitted by a blackbody is a function of its temperature and the wavelength.  From these curves you should be able to identify two properties of radiant energy

1. at a given wavelength, the radiance is a monotonically increasing function of temperature (in other words, at a given wavelenth the amount of radiant energy from a blackbody always increases with temperature)
2. at a given temperature there is one wavelength where the radiant enery peaks, and as temperature increases, this wavelength gets shorter.  

You should also be aware of the fact that if you integrate Planck's function over all wavelengths (in other words, if you take the area under any given temperature curve) you will get the Stefan-Boltzman relationship of the total radiant exitance from the blackbody, which we discussed previously:

Now that we have considered

1. the way the radiant energy varies with wavelength and temperature, and
2. knowing that temperature varies with height in the atmosphere, and that
3. atmospheric gases (like water vapor and carbon dioxide and ozone) absorb (and therefore emit) radiation in specific wavelengths.....

we are finally ready to consider how radiometers can resolve vertical structure in the atmosphere.  

The GOES 8/9 sounding instruments are 19 channel filter wheel radiometers.  The GOES- Sounder,  using a rotating filter wheel for channel selection, can sense radiance in 18 infrared wavelength bands and it has one visible channel for cloud detection. The sounder and imager instruments on the GOES platform operate simultaneously.   The 19 sounder radiometer spectral channels are described in the attached Table.  

CIMSS Sounder Tutorial

The following material links us to a tutorial prepared by the Cooperative Institute for Meteorological Satellite Studies (CIMSS) at the Space Science and Engineering Center (SSEC), University of Wisconsin, Madison.  The general site for CIMSS can be linked off the EVSC494 links page.  

Introducing the GOES-8 Sounder

• Introduction
• Description of the Sounder
• Profile Retrieval Information
• Example of Profile Retrievals
• Derived Product Images
• NMC Model with and without GOES Sounder Data
• Practical Implications of the GOES-8 Sounder

This GOES-8 Sounder tutorial is a product of the Cooperative Institute for Meteorological Satellite Studies (CIMSS ), located at the University of Wisconsin-Madison. CIMSS is a cooperative institute formed through a memorandum of understanding between the University of Wisconsin-Madison, the National Oceanic and Atmospheric Administration (NOAA) and the National Aeronatics and Space Administration (NASA). This material was prepared by the National Environmental Satellite Data and Information Service (NESDIS) System Design and Applications Branch together with University scientists within CIMSS.

Last Modified: 09-Jan-95

Discussion of Real-time GOES Derived Products

Summary of GOES Sounder Channels and Applications

This summary is taken from the CIMSS/COMET SAT/MET class tutorial on the GOES Sounder

The radiative transfer equation (RTE) illustrates that the upwelling radiance is a function of the atmospheric temperature (through the Planck function) and the gaseous composition of the atmosphere which influences the transmittance.  Recall that the transmittance will be determined by the absorption coefficient and density profile of the relevant absorbing gas (at the specified wavelength).

The RTE equation is an ill-conditioned mathematical problem when it comes to reteiving temperature values from within this integral operator, there is no unique solution.  Several inversion techniques have been used to solve sets of spectrally independent radiative transfer equations (matrix inversion, numerical iteration of linearized equations, etc.).  These advanced topics are left for the motivated student to pursue.  However, we can conceptually summarize a solution approach with the following: 

Sounder Channel Response Functions and Standard Atmosphere Absorption

• Radiance arises from deep and overlapping layers in the atmosphere
• Radiance observations are not independent
• We cannot define a unique relation between the spectrum of outgoing radiance and T(p) or Q(p) (where Q is water vapor content)
• T(p) is buried in the exponent of the demoninator in the radiative transfer equation (RTE) integral
• The moisture profile (Q(p)) is implicit in the amount of transmittance
• A first guess is required to derive a solution to the RTE (we get this from a numerical forecast model)

Recent BAMS Article on GOES Sounder Applications

 Back to Syllabus