SCILOV-10 Validation of SCIAMACHY nadir operational NO 2 product F. Azam, A. Richter, M. Weber, H. Bovensmann and J. P. Burrows ESA/ESRIN, Frascati, Italy

Contents:  Datasets  NO 2 total column inter-comparisons Relative differences Bias  Conclusion/Outlook 1

ESA /DLR (SCIAMACHY) vs IUP(SCIAMACHY and GOME2) NO 2 main retrieval differences 2 ESA/DLR v5.02 IUP (SCIA+GOME2) Processors: BIRA-IASB (SDOAS) IUP (DOAS) Spectral range nm 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

3 ESA/DLR and IUP SCIAMACHY : ESA/DLR and IUP SCIAMACHY NO 2 monthly mean zonal means (5°x5° latitude bins) ESA/DLR amounts relatively higher than IUP at high latitudes

4 Relative differences comparisons: Relative differences between the monthly mean zonal means of ESA/DLR and IUP SCIAMACHY NO 2 datasets for the time span  In general very good agreement within ±5%  differences at high latitudes reach ~15% (ESA-IUP)/IUP

5 ESA/DLR SCIAMACHY and GOME2 : ESA/DLR SCIAMACHY and IUP GOME2 NO 2 monthly mean zonal means (5°x5° latitude bins) ESA/DLR amounts higher than GOME2 at higher latitudes and tropics

6  At higher latitudes and tropics, seasonality in differences, reaches +20 %  elsewhere good agreement within 5% Relative differences comparisons: Relative differences between the monthly mean zonal means of ESA/DLR SCIAMACHY and IUP GOME2 NO 2 datasets for the time span (ESA-GOME2)/GOME2

13 Bias comparisons: Relative differences between the monthly mean zonal means of ESA/DLR and IUP SCIAMACHY NO 2 datasets averaged over the time span  almost stable offset with a strong statistical dispersion at higher latitude  insignificant bias of ~ 0.8%.

13 Bias comparisons: Relative differences between the monthly mean zonal means of ESA/DLR SCIAMACHY and IUP GOME2 NO 2 datasets averaged over the time span  positive bias ~ 6%  significant offset at ~ 40 – 60N

9 Conclusions  ESA/DLR SCIAMACHY NO 2 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

10 Outlook/Recommendations  Comparisons of NO 2 with ground based measurments  Studies on scan angle dpendency should be a part of future operational nadir validation activities.

Thank You