Validation of SCIAMACHY polarisation using POLDER as a reference (bonus: reflectance validation)...
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Transcript of Validation of SCIAMACHY polarisation using POLDER as a reference (bonus: reflectance validation)...
![Page 1: Validation of SCIAMACHY polarisation using POLDER as a reference (bonus: reflectance validation) Tiger Team Meeting 23, SRON, 23 May 2006.](https://reader036.fdocuments.us/reader036/viewer/2022062417/551b1d1f5503462e578b610e/html5/thumbnails/1.jpg)
Validation of SCIAMACHY polarisation using POLDER as a reference
(bonus: reflectance validation)
Tiger Team Meeting 23, SRON, 23 May 2006
![Page 2: Validation of SCIAMACHY polarisation using POLDER as a reference (bonus: reflectance validation) Tiger Team Meeting 23, SRON, 23 May 2006.](https://reader036.fdocuments.us/reader036/viewer/2022062417/551b1d1f5503462e578b610e/html5/thumbnails/2.jpg)
POLDER• imager• CCD detector matrix• bandfilter carousel• wide FOV lens
• resolution: 6 × 7 km2
• polarisation at 443,
670, and 865 nm• well-calibrated
443, 443, 490, 565, 670, 763, 765, 865, 910 nm
![Page 3: Validation of SCIAMACHY polarisation using POLDER as a reference (bonus: reflectance validation) Tiger Team Meeting 23, SRON, 23 May 2006.](https://reader036.fdocuments.us/reader036/viewer/2022062417/551b1d1f5503462e578b610e/html5/thumbnails/3.jpg)
Intercomparison: SCIAMACHY versus POLDER look for collocated data (position, time) with identical viewing geometry
a. POLDER image (reflectance @ 670 nm) + previous images
b. POLDER viewing angles (in green). In black: SCIAMACHY nadir pixels of 1.0 s IT
c. POLDER viewing angles for data where the viewing geometry is similar to SCIAMACHY’s
d. For the same measurement data again the reflectance @ 670 nm. In white: SCIAMACHY nadir pixels of 0.25 s IT
Data can be compared
![Page 4: Validation of SCIAMACHY polarisation using POLDER as a reference (bonus: reflectance validation) Tiger Team Meeting 23, SRON, 23 May 2006.](https://reader036.fdocuments.us/reader036/viewer/2022062417/551b1d1f5503462e578b610e/html5/thumbnails/4.jpg)
Reflectance: spectral averaging --- IT = 0.25 s
--- IT = 1.00 s
transform SCIAMACHY reflectance into 9 broadband values for comparison with POLDER broadband reflectance measurements
![Page 5: Validation of SCIAMACHY polarisation using POLDER as a reference (bonus: reflectance validation) Tiger Team Meeting 23, SRON, 23 May 2006.](https://reader036.fdocuments.us/reader036/viewer/2022062417/551b1d1f5503462e578b610e/html5/thumbnails/5.jpg)
Results for the reflectance: (SCIAMACHY s/w version 5.01)
× = cloudy
+ = cloud-free
Cloudy data are less reliable; fit results for cloud-free data
Slope ≠1 (known) calibration problem of SCIAMACHY
![Page 6: Validation of SCIAMACHY polarisation using POLDER as a reference (bonus: reflectance validation) Tiger Team Meeting 23, SRON, 23 May 2006.](https://reader036.fdocuments.us/reader036/viewer/2022062417/551b1d1f5503462e578b610e/html5/thumbnails/6.jpg)
Reflectance: comparison with other “sources”
10–20% error in radiometric calibration….
![Page 7: Validation of SCIAMACHY polarisation using POLDER as a reference (bonus: reflectance validation) Tiger Team Meeting 23, SRON, 23 May 2006.](https://reader036.fdocuments.us/reader036/viewer/2022062417/551b1d1f5503462e578b610e/html5/thumbnails/7.jpg)
Results (polarisation) (SCIAMACHY s/w version 5.01)
× + = water
× + = land
• PMD 2: something is wrong, bad correlation
• PMD 3: looks better, but look at the slope
• PMD 4: a lot of serious errors
polarisation product of bad quality
much better than version 4.01, though
IT = 0.25 s
![Page 8: Validation of SCIAMACHY polarisation using POLDER as a reference (bonus: reflectance validation) Tiger Team Meeting 23, SRON, 23 May 2006.](https://reader036.fdocuments.us/reader036/viewer/2022062417/551b1d1f5503462e578b610e/html5/thumbnails/8.jpg)
PMD 4: simple check
IT = 0.25 s
- zero-point problem
- “unphysical” values
![Page 9: Validation of SCIAMACHY polarisation using POLDER as a reference (bonus: reflectance validation) Tiger Team Meeting 23, SRON, 23 May 2006.](https://reader036.fdocuments.us/reader036/viewer/2022062417/551b1d1f5503462e578b610e/html5/thumbnails/9.jpg)
Conclusions
• radiometric calibration SCIAMACHY contains errors• reflectance 10-20% too low in visible wavelength range• for the first time successful polarisation intercomparison• polarisation errors for PMD 2 and 3• polarisation retrieval of PMD 4 is in a very bad shape
![Page 10: Validation of SCIAMACHY polarisation using POLDER as a reference (bonus: reflectance validation) Tiger Team Meeting 23, SRON, 23 May 2006.](https://reader036.fdocuments.us/reader036/viewer/2022062417/551b1d1f5503462e578b610e/html5/thumbnails/10.jpg)
EXTRA SLIDES: PMD 4 versus single scattering value: Q/I and U/I
IT = 0.25 s
IT = 1.00 s