1. Quick Review of Remote Sensing Basic Theory Paolo Antonelli CIMSS University of Wisconsin-Madison South Africa, April 2006

2. Outline IR at High Spectral Resolution Basic Principles Limits in IR remote sensing

3. Visible (Reflective Bands) Infrared (Emissive Bands) High Spectral Resolution

4. High Vertical Resolution

5. Radiative Transfer Equation

6. Transmittance for an off-line Channels z  1  close to 1 a close to 0 z1z1 z2z2 z3z3  + a + r = 1 The molecular species in the atmosphere are not very active: most of the photons emitted by the surface make it to the Satellite if a is close to 0 in the atmosphere then  is close to 0, not much contribution from the atmospheric layers Surface emission Atmospheric emission T(z 1 ) T(z 2 ) T(z 3 )

7. Trasmittance on an Absorption Line z  1 z1z1 z2z2 z3z3 Absorption Channel:  close to 0 a close to 1 One or more molecular species in the atmosphere is/are very active: most of the photons emitted by the surface will not make it to the Satellite (they will be absorbed) if a is close to 1 in the atmosphere then  is close to 1, most of the observed energy comes from one or more of the uppermost atmospheric layers z4z4 T(z 4 ) T(z 3 ) T(z 2 ) T(z 1 )

8. Weighting Functions  1 z1z1 z2z2 zNzN d  /dz z1z1 z2z2 zNzN

9. What Causes Absorption? Molecules in the Atmosphere. For any layer of the atmosphere, molecular absorption determines the layer emissivity and trasmittivity

10. CO 2 Lines

11. H 2 O Lines

12. Vibrational Lines CO 2 O3O3 H2OH2O

13. Rotational Lines CO 2 O3O3 H2OH2O

14. HeIghtHeIght AbsorptionAbsorption Wavenumber Energy Contribution Weighting Functions

15. Line Shape: Pressure Dependence

16. Broad Band window CO 2 O3O3 H2OH2O window Samplig of vibrational bands Integration over rotational bands

17. … in Brightness Temperature

18. High Spectral Resolution Samplig over rotational bands

19. AIRS and MODIS (mt Etna, Sicily, 28 Oct 2002)

20. Broad Band vs High Spectral

21. Questions For a given water vapor line what happens to its weighting function When the amount of upper tropospheric water vapor increases?

22. Tau 100% 0 For a given water vapor spectral channel Wet Atm. Dry Atm. Dry Wet Moderate Weighting Function HEIGHTHEIGHT

23. Questions How does it look the observed spectrum for high thick water vapor cloud ?

24. Thick Cloud Opacity

25. Questions Moving deeper and deeper into an absorption line the observed BT tends do decrease, why? Is it always true that the BT decreases going deeper into the absorption band?

26. Temperature Inversions AIRS (20 July 2002) calculation Sub-Arctic Winter May 2001 S. Pole radiosonde profile used in calculation (0.365 mm H 2 O)

27. Conclusions High Spectral Resolution High Vertical Resolution Large Volume of Data (redundancy)