SatMet Home PageIn this lab, we will use the results of a "forward model" for radiative transfer which provides equivalent brightness temperatures in the GOES Sounder channels from given atmospheric profiles of temperature and humidity.
I. Analysis of model results (20 min lab ; 10 min discussion)
The first step in the exercise is to review the discussion material and sensitivity test data from the forward model.
II. Interpretation of channel relationships and sensitivity (45 min lab)
After reviewing this information, consider the following questions, and answer them by referring back to the information pages and images (It helps to open a second browser window):
1. For a dry atmosphere, which channel (1, 2, 3, 4, or 5) is most sensitive to CO2 absorption? Try to answer this by using the weighting functions.
2. For a dry atmosphere, which channel has the greatest change in brightness
temperature (Tb) for a 10 C increase in surface skin temperature? (Click here)
Why would you expect this channel to respond the most? Is the value of the Tb change
similar for a humid atmosphere? Why or why not?
Repeat these questions for a 10 C increase in 700 mb air temperature. (Click here)
3. For a dry atmosphere, does a 10 C change in temperature at 300 hPa cause
more change in the H2O-sensitive bands (6, 10-12, 18) or the CO2-sensitive bands (1-5,
13-15)? (Click here)
What does this tell you about the relative effect of atmospheric absorption of CO2 and H2O
on satellite-observed brightness temperatures in these bands?
4. For a dry atmosphere, which channel (10, 11, or 12) is most sensitive to
H2O absorption? Infer this from the weighting functions. (Click here)
In which channel would you expect the largest change in Tb to be caused by 10 C increase
in the 500 hPa dewpoint depression (drying). (Click here)
Questions 5 and 6 are tricky (Extra Credit).
5. How can an increase in the 700 hPa dewpoint depression (drying) result in
a colder window channel (Ch8) Tb? Hint: Consider the temperature sounding. (Click here)
6. Does moisture increase or decrease the CO2 channel sensitivity to changes in atmospheric temperature? (Click here)
III. Summary Discussion (15 min)
