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SCIAMACHY v6.02 reflectance and the resulting Absorbing Aerosol Index. L.G. Tilstra 1,2 , M. de Graaf 2 , I. Aben 1 , P. Stammes 2 1 SRON; 2 KNMI. Outline. Absorbing Aerosol Index (AAI) and the residue Reflectance: version 6.02 versus version 5.04 Effects of degradation in the AAI / residue

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sciamachy v6 02 reflectance and the resulting absorbing aerosol index

SCIAMACHY v6.02 reflectance and the resulting Absorbing Aerosol Index

L.G. Tilstra1,2, M. de Graaf2, I. Aben1, P. Stammes2

1SRON; 2KNMI

outline
Outline
  • Absorbing Aerosol Index (AAI) and the residue
  • Reflectance: version 6.02 versus version 5.04
  • Effects of degradation in the AAI / residue
  • Conclusions

All results shown apply to the scientific product (SC-AAI).

absorbing aerosol index aai and the residue
Absorbing Aerosol Index (AAI) and the residue
  • Definition of the residue:
  • where the surface albedo A for the simulations is such that:
  • no clouds, no absorbing aerosols : r < 0
  • clouds, no absorbing aerosols : r < 0
  • absorbing aerosols, no clouds : r > 0
  • B. Definition of the AAI:
  • AAI = residue > 0 (where residue < 0 the AAI is not defined)
slide4
AAI in 2004:(monthly mean)Normal distribution of UV-absorbing aerosols. Similar to observations by TOMS.

AAI in 2006:(monthly mean)Degradation of the opticsleads to anomalously highvalues of the residue / AAI.

sciamachy gome aai data are available on the temis website
SCIAMACHY & GOME AAI data are available on the TEMIS website

http://www.temis.nl

Available data:

GOME

SCIA

: 1995–2000

: 2002–2006

2 reflectance version 6 02 vs 5 04
(2) Reflectance: version 6.02 vs 5.04

6.02/5.04

Correction factor from comparison with:

× = DAK

+ = MERIS

O = POLDER

3 degradation of the residue
(3) Degradation of the residue

Global monthly means:

Global monthly average of residue should be ~constant and should lie between -2 and -1

slide8
Degradation of the reflectance: “Light Path Monitoring” results from Stefan Noël(for the wavelengths 340 and 380 nm relevant to the AAI)

c380

c340

effect of instrument degradation c 340 c 380 on residue aai
Effect of instrument degradation (c340 ; c380) on residue/AAI:
  • Trend in residue can be explained by degradation as found from “Light Path Monitoring” results.
  • Residue/AAI is very sensitive to (absolute) reflectance calibration.
  • Degradation correction is really important for the AAI.
  • Residue is recording its own degradation correction
conclusions
Conclusions:
  • Absolute calibration of the reflectance has improved with v6.02, but the calibration problem is still not solved
  • AAI and residue are very sensitive to the radiometric calibration and therefore suited for monitoring degradation of the optics
  • Effects of degradation in the residue/AAI are found, and can be explained by degradation from “Light Path Monitoring” results.
  • A proper degradation correction is essential for the AAI.