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SCILOV-10 Validation of SCIAMACHY n adir operational NO 2 product

SCILOV-10 Validation of SCIAMACHY n adir operational NO 2 product. F. Azam , A. Richter, M. Weber, H. Bovensmann and J. P. Burrows ESA/ESRIN, Frascati , Italy 26-02-2014. Contents: Datasets N O 2 total column inter-comparisons Relative differences Bias

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SCILOV-10 Validation of SCIAMACHY n adir operational NO 2 product

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  1. SCILOV-10 Validation of SCIAMACHY nadir operational NO2 product F. Azam, A. Richter, M. Weber, H. Bovensmann and J. P. Burrows ESA/ESRIN, Frascati, Italy 26-02-2014

  2. Contents: • Datasets • NO2 total column inter-comparisons • Relative differences • Bias • Conclusion/Outlook 1

  3. ESA /DLR (SCIAMACHY) vs IUP(SCIAMACHY and GOME2) NO2 main retrieval differences ESA/DLR v5.02 IUP (SCIA+GOME2) Processors: BIRA-IASB (SDOAS) IUP (DOAS) Spectral range 426.5-451.5nm 425 -450 nm Max. SZA 89° 85° AMF LIDORT code SCIATRAN Cloud parameters OCRA/SACURA FRESCO See for details; Richter et al. 2005, 2011 and SCIAMACHY Level 2 version5.02 products Readme file 2

  4. ESA/DLR and IUP SCIAMACHY : • ESA/DLR and IUP SCIAMACHY NO2 monthly mean zonal means (5°x5° latitude bins) • ESA/DLR amounts relatively higher than IUP at high latitudes 3

  5. Relative differences comparisons: • Relative differences between the monthly mean zonal means of ESA/DLR and IUP SCIAMACHY NO2 datasets for the time span 2002-2012. (ESA-IUP)/IUP • In general very good • agreement within ±5% • differences at high • latitudes reach ~15% 4

  6. ESA/DLR SCIAMACHY and GOME2 : • ESA/DLR SCIAMACHY and IUP GOME2 NO2 monthly mean zonal means (5°x5° latitude bins) • ESA/DLR amounts higher than GOME2 at higher latitudes and tropics 5

  7. Relative differences comparisons: • Relative differences between the monthly mean zonal means of ESA/DLR SCIAMACHY and IUP GOME2 NO2 datasets for the time span 2007-2012. (ESA-GOME2)/GOME2 • At higher latitudes and • tropics, seasonality • in differences, reaches • +20 % • elsewhere good • agreement within 5% 6

  8. Bias comparisons: • Relative differences between the monthly mean zonal means of ESA/DLR and IUP SCIAMACHY NO2 datasets averaged over the time span 2002-2012. • almost stable offset with a strong statistical dispersion at higher latitude • insignificant bias of ~ 0.8%. 13

  9. Bias comparisons: • Relative differences between the monthly mean zonal means of ESA/DLR SCIAMACHY and IUP GOME2 NO2 datasets averaged over the time span 2007-2012. • positive bias • ~ 6% • significant offset at • ~ 40 – 60N 13

  10. Conclusions • ESA/DLR SCIAMACHY NO2 total column v5.02 compared with scientific IUP products derived from SCIAMACHY and GOME2 measurements • The SCIAMACHY datasets agree quite well (~5%) with the exception of high latitudes where the differences can reach 15% • Probable reasons: differences in max. limit of SZA, the differences in the • air mass factors and input as cloud parameters etc • ESA/DLR and GOME2 data show large differences at tropics and high latitudes that can reach 20%; significant offset ~6.0% observed around • 40-60N • Possible reasons: differences in overpass time, differences in max. limit of SZA, the differences air mass factors, input to the processors. SCIAMACHY captures more structured tropospheric signals due to its better spatial resolution, this could explain large differences observed at the tropics • 9

  11. Outlook/Recommendations • Comparisons of NO2 with ground based measurments • Studies on scan angle dpendency should be a part of future operational nadir validation activities. • 10

  12. Thank You

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