1. The Aqua-MODIS calibration transfer using DCC
David Doelling, Conor Haney, Ben Scarino, Rajendra Bhatt, Arun Gopalan
GSICS Annual Meeting, Darmstadt Germany, March 24-28, 2014

2. 2 methods to transfer the Aqua-MODIS calibration to GEO using DCC
Aqua-MODIS BRDF corrected DCC multi-year mode radiance over the GEO domain
only use GEO DCC during Aqua overpass times
Assume the same DCC are captured by both Aqua-MODIS and GEO, although not exactly coincident and by the same viewing conditions
Rely on DCC BRDF model to remove sampling dependencies
Use the month to month DCC mode radiance, to remove seasonal cycle present in both Aqua and GEO
Applicable to historical instruments
Aqua-MODIS/GEO DCC raymatching
Similar to Aqua-MODIS/GEO all-sky ray-matching except restrict only to DCC identified regions
Use coincident angle matched DCC radiance pairs

3. Aqua-MODIS BRDF corrected DCC mode radiance over GEO domain
Use same GEO and Aqua-MODIS criteria to obtain the MODIS monthly BRDF corrected DCC mode radiance over the GEO domain

4. Aqua-MODIS BRDF corrected DCC mode radiance
The 10-year DCC mode radiance over the GEO domain is the predicted DCC radiance
GEO and MODIS must have same selection criteria
Maybe the monthly mode radiance variability is correlated to the GEO variability
A 0.7% difference in MODIS DCC mode radiance is observed for a 5°K temperature however, the trend was identical

5. DCC mode radiance comparison over 140° East GEO domain
GEO calibrated by ray-match with MODIS
• Aqua-MODIS C6
• NPP-VIIRS Land PEATE calibration
Global DCC mode radiance
• Terra DCC trend half of Aqua

6. Possible explanations
Aqua-MODIS and NPP-VIIRS monthly DCC frequency
Aqua and NPP in same orbit, 45 minutes apart
Aqua-MODIS C6-C5 B13 (11µm) temperature difference
C6 vis
C5 IR
• Aqua-MODIS C5 warmer and therefor lower DCC mode radiance

7. DCC mode radiance comparison over 0° East GEO domain
• The DCC temporal variability is somewhat similar

8. DCC mode radiance comparison over 140° East GEO domain
• GEO and MODIS DCC frequency is some what similar

9. DCC mode radiance comparison with independent methods
MTSAT-2 RT and DCC
GOES -12 Desert and DCC
0.6% difference
0.4% difference
• These results use the 10 year mode radiance

10. MTSAT-2/Aqua-MODIS raymatching using all 0.5° lat/lon regions
SBAF based on radiance applied

11. Is the ray-match monthly scatter or timeline noise due to spectral differences
• The DCC SBAF correction is very small
• Will DCC ray-matching reduce noise?
• Will there be enough samples?

12. DCC ray-matching Regress monthly Aqua-MODIS/GEO visible radiance pairs
Identify DCC cells in Aqua 1-km pixel level data
Use several cell sizes to find optimum size
The mean pixel level temperature < 205°K
Compute standard deviation of pixel level visible radiances and temperatures of both the core pixels and the adjacent pixels.
Using GEO angle prediction software, determine if the MODIS and GEO view and azimuthal angles are within 15°
Write out MODIS center latitude and longitude and time
Based on MODIS time and navigation order GEO images within 15 minutes to compute similar statistics as MODIS
To avoid cell overlap over an image, start with the coldest cell and remove adjacent cells within coldest cell
Regress monthly Aqua-MODIS/GEO visible radiance pairs
Use various thresholds and cell sizes to find lowest standard error

13. View angle MODIS GOES-E LEO glint Azimuth angle GEO glint
IR matched regions
MODIS
GOES-E
LEO glint
Azimuth angle
GEO glint
VIS matched regions

14. Predictor Enhancements

15. Raymatching
302-km
92-km
1° lat/lon grid, MTSAT-2, July 20, :32 GMT

16. MTSAT-2, 302-km FOV
No filtering
VZA<35°, s<10%

17. MTSAT-2, 302-km FOV
Feb 2012
0.8% s
0.5831
Mar 2012
0.6% s
0.5727
Gain changes
Feb s=0.8%
-1.8%
Mar s=0.6%
+2.0%
Apr s=1.2%
-2.4%
May s=0.9%
+4.3%
July 1.6%
Apr 2012
1.2% s
0.5842
May 2012
0.9% s
0.5699

18. MTSAT-2/Aqua-MODIS April 2012 raymatched radiance pairs
All-sky ocean
DCC 92km
DCC 302km
.5772
.5847
.5842
• DCC raymatch results very similar

19. MTSAT-2/Aqua-MODIS monthly raymatch timelines
All-sky ocean
9-km
30-km
.5791
.5853
.5837
• ~1% difference in the overall absolute calibration between DCC and all-sky ocean ray-match
• ~0.3% difference between various DCC ray-matching selection thresholds

20. Conclusions
Plan is to use DCC ray-matching in the short term for current operational DCC calibration
Compare with 10 year mean DCC mode radiance given to GPRCs
Long term plan is to derive an annual (long-term) GEO domain specific DCC mode radiance
Verify by DCC ray-matching
Look at all dependencies, such temperature
Look into seasonal dependencies, BRDF
Learn from comparing MODIS and VIIRS domain specific DCC mode radiance