1. Hyperspectral Cloud Top Retrievals
Robert E. Holz, Steve Ackerman, Matthew McGill,
Paolo Antonelli and Fred Nagle

2. Overview
Part 1. CO2 Sorting + Slicing cloud height retrieval validation
Part 2. Night time polar cloud height detection using AIRS hyperspectral measurements

3. CO2 Channel Selection Algorithm (CO2 Sorting)
The Sorted Clear Sky Spectrum
These figures show the channels used for the CO2 sorting (Left figure) and the effect of sorting the channels (right figure) for clear scene case
-Sort from coldest to warmest BT
-creat the sorted index which his aplied to all scene including clouds

4. CO2 Sorting: Sensitivity to Brightness Temperature
High and Thick Cloud
Thinner Cloud
Low Cloud
High and Thick Cloud
Thinner Cloud
High and Thick Cloud
Major points to talk about:
Effect of adding clouds to the sorted spectrum
Information about the cloud height (inflection point) and optical thickness (slope)
This figure demonstrates the signature of different cloud scenes. The first channel that “sees” the cloud will start to diverge from the sorted clear sky scene. For the high thick cloud this occurs at approximately 230 K. The slope of the sorted spectrum also has information about the cloud optical thickness. A sorted spectrum that quickly diverges from the clear sky scene represents a thick cloud. In contrast, a thin high cloud will have a more gradual slope is demonstrated in the figure. The cloud high algorithm looks to see if there is a divergence from the clear sky spectrum. The brightness temperature of the first channel that diverges beyond a pre-set threshold is determined the cloud top temperature. Using a pressure and temperature profile the cloud pressure level can be determined. Will talk about the problems with this approach.

5. Selected CO2 Channels
High Cloud
Mid Level Cloud

6. February 22, 2003

7. S-HIS - CPL February 22, 2003

8. S-HIS - CPL Cloud OD < 1.0
(km)

9. S-HIS Cloud Top OD Sensitivity
0.2
0.4
0.6
0.8
1.0
1.2
CPL OD Contours .
SHIS - CPL
SHIS Cloud Top Retrieval
Altitude

10. S-HIS Cloud Top OD

11. Distribution of S-HIS Cloud Level Optical Depth February 22
CPL optical depth at the S-HIS cloud height

12. Part 2: Night Time Polar Cloud Height Retrievals Using AIRS Hyperspectal Measurements

13. Polar Cloud Height Retrieval Problem
One BT could be 3 different cloud heights

14. AIRS Polar Cloud Height Retrieval 14:00 UTC

15. Conclusions and Future Plans
The combined CO2 slicing + sorting cloud top retrieval improves the CO2 slicing results for optically thin clouds
Lidar retrieved integrated cloud optical depth is a more representative measure of cloud top retrieval performance.
It is possible to detect temperature inversions above arctic stratus using hyperspectral measurements
The inversion information reduces the uncertainty in the arctic stratus IR cloud top retrievals
Future:
Apply the CO2 sorting + slicing retrieval to AIRS satellite data
Integrate the CO2 sorting + slicing retrieval with the arctic inversion detection