1. A practical guide to IR and MW radiative transfer using the RTTOV model and GUI Practical exercises

2. Start up the RTTOV GUI
type:
rttovgui
Class01,trd00, 2tDQohR,

3. Exercise #1 – run RTTOV direct model for AMSU-A MW sounder
File/Open Profile to select and Open Diverse_profile_set.h5 and select profile 1.
RTTOV/Load Coefficients to Choose and Open and Load AMSU-A RTTOV coefficients rtcoef_metop_2_amsua.dat from coefficients directory
RTTOV/Run RTTOV direct to run the direct model. The Radiance Viewer is displayed showing the brightness temperature in each AMSU-A channel.
Windows/Surface Editor Window to view surface and other input variables. Modify skin temperature.
RTTOV/Run RTTOV direct to run the direct model again (do not close the Radiance Viewer window between runs!) In the Radiance Viewer select --Pseudo run--/run_02 minus run_01 to see the difference.
Windows/Profile Editor Window to view temperature and gas profiles. Modify temperature profile near the tropopause (~50-200hPa).
RTTOV/Run RTTOV direct to run the direct model again (do not close the Radiance Viewer window between runs!) In the Radiance Viewer select --Pseudo run--/run_03 minus run_02 to see the difference.

4. GUI main control window

5. GUI pull down menus

6. Open a profile

7. Open a profile

8. Open a profile

9. Open a profile Select Diverse_profile_set.h5

10. Open a profile

11. Open a profile Select profile 1 from the list

12. Open a profile

13. Choose and Load AMSUA (RT) coefficients

14. Choosing (RT) coefficients

15. Choosing (RT) coefficients

16. Choosing (RT) coefficients

17. Choosing (RT) coefficients

18. Choosing (RT) coefficients

19. Loading (RT) coefficients

20. Run RTTOV direct

21. Radiance Viewer – Overview (Some options will make more sense in a moment after running more simulations – don’t close the Radiance Viewer window!)
Select between brightness temperature and radiance
Plot results for a single channel for all runs performed so far.
Choose which run to display (after doing multiple simulations)
Plot differences between runs or compare two runs on the same plot
Choose which run is the reference for the “Pseudo run” comparisons
By default plot shows brightness temperatures in each channel for the most recent simulation performed.

22. Open Surface Editor Window

23. Modify Skin Temperature to 330K

24. Apply the change

25. Re-run RTTOV direct (Don’t close the Radiance Viewer between runs!)

26. In Radiance Viewer plot difference between the two runs

27. In Radiance Viewer plot difference between the two runs
The differences are shown in red.
The scale is on the right side of the plot.
Notice which channels show a change in brightness temperature and which show no change.
Compare this with the weighting functions plotted on the following two slides.

28. AMSU-A weighting functions for a selection of surface-sensitive channels

29. AMSU-A weighting functions for a selection of channels insensitive to the surface

30. Open Profile Editor Window

31. Profile Editor Window - Overview
After making changes select Apply change in File menu
Undo/Redo and other editing options available in Edit menu
View temperature and gas profiles individually using the tabs
Right-click in this window to modify profile values on individual levels
All input profiles are shown together here
NB ozone and CO2 profiles are ignored for MW simulations
Select the zoom tool and drag a box on the plot to enlarge an area

32. Edit temperature profile near tropopause
Ensure Temperature tab is selected here

33. Edit temperature profile near tropopause
Edit values to scale temperature profile by a factor of 1.05 between pressure levels of 50 and 200hPa then select OK

34. Apply the change

35. Re-run RTTOV direct (Don’t close the Radiance Viewer between runs!)

36. In Radiance Viewer plot difference between the last two runs

37. In Radiance Viewer plot difference between the last two runs
Again notice which channels show the largest changes.
Those channels whose weighting functions peak within or near the hPa region show the largest BT differences (see next slide).
Other channels show limited sensitivity to the temperature change.

38. AMSU-A weighting functions for a selection of channels insensitive to the surface

39. Exercise #2 – run RTTOV direct and K models for IASI high resolution IR sounder
File/Open Profile to select and Open Diverse_profile_set.h5 and select profile 52.
RTTOV/Load Coefficients to Choose and Open and Load IASI RTTOV coefficients rtcoef_metop_2_iasi.dat from coefficients directory.
Windows/Options Editor Window to view RTTOV configuration options. Ensure “ozone_data”, “switchrad” options are checked.
Windows/Surface Editor Window to view surface and other input variables. Ensure surface type is set to Land.
RTTOV/Run RTTOV direct to run the direct model. The Radiance Viewer is displayed showing the IASI brightness temperature spectrum.
Windows/Profile Editor Window to view temperature and gas profiles. Modify ozone profile.
RTTOV/Run RTTOV direct to run the direct model again (do not close the Radiance Viewer window between runs!) In the Radiance Viewer select --Pseudo run--/run_02 minus run_01 to see the difference which highlights which parts of the IASI spectrum are sensitive to ozone.
RTTOV/Run RTTOV K to run the K model. Examine some individual Jacobians in different parts of the spectrum using the “kP” button.

40. Open a profile

41. Open a profile

42. Open a profile

43. Open a profile Select Diverse_profile_set.h5

44. Open a profile

45. Open a profile Select profile 52 from the list

46. Open a profile

47. Choose and Load IASI (RT) coefficients

48. Choosing (RT) coefficients

49. Choosing (RT) coefficients

50. Choosing (RT) coefficients

51. Choosing (RT) coefficients

52. Choosing (RT) coefficients

53. Loading (RT) coefficients
rtcoef_metop_2_iasi.dat

54. Open Options Editor Window

55. Open Options Editor Window
ozone_data – enables ozone as a variable gas in the simulations.
switchrad – Jacobians are calculated with respect to BT (if true) rather than radiance (if false).
Ensure “ozone_data” and “switchrad” options are checked and then click “Apply”.

56. Open Surface Editor Window

57. Modify SURFTYPE to Land

58. Apply the change

59. Run RTTOV direct

60. Run RTTOV direct
Hover mouse cursor over plot to display channel number, wavenumber/wavelength and simulated BT

61. Open Profile Editor Window

62. Edit ozone profile Ensure Ozone tab is selected here
NB For this coefficient file CO2 is not active as a variable trace gas

63. Edit ozone profile
Edit value to scale the entire ozone profile by a factor of 1.05 then select OK

64. Apply the change

65. Re-run RTTOV direct (Don’t close the Radiance Viewer between runs!)

66. In Radiance Viewer plot difference between the two runs

67. In Radiance Viewer plot difference between the two runs
Main ozone band is around 9.5µm (~1050cm-1)

68. Run RTTOV K

69. K Matrix Viewer - Overview
Scroll left/right by one page
Scroll left/right by 80 channels
Plot Jacobians for a specific channel
Hover mouse cursor over each plot to display detailed information in status bar

70. Display Jacobians for ch1640 (ozone channel)

71. Display Jacobians for ch1640

72. Display Jacobians for ch1640
View temperature and gas Jacobians individually using the tabs
All Jacobians are shown together here
NB CO2 is not an active gas for this coefficient file
This channel is insensitive to water vapour
Skin temperature Jacobian

73. Display Jacobians for ch1640
The ozone Jacobian is negative i.e. increasing the ozone concentration decreases the satellite-seen radiance.
Can you explain why the ozone Jacobian is negative in the troposphere, but close to zero in the stratosphere?
Hint: consider the temperature profile and what would happen in terms of absorption and emission if the ozone concentration were increased at different pressure levels.

74. Plot the Jacobians for some other channels
For example:
ch3500 water vapour channel, similar to the ozone case
ch94 CO2 channel, this band can be used for temperature sounding
If you have time you can also run the Jacobian model for the AMSUA coefficient file