SCILOV-10Validation of SCIAMACHY nadir

operational NO2 product

F. Azam, A. Richter, M. Weber, H. Bovensmann and J. P. Burrows

ESA/ESRIN, Frascati, Italy26-02-2014

Contents:

Datasets

NO2 total column inter-comparisons

Relative differences

Bias

Conclusion/Outlook

1

ESA /DLR (SCIAMACHY) vs IUP(SCIAMACHY and GOME2) NO2 main retrieval differences

2

ESA/DLR v5.02 IUP (SCIA+GOME2)

Processors: BIRA-IASB (SDOAS) IUP (DOAS)

Spectral range 426.5-451.5 nm 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

3

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

4

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.

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 NO2 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 NO2 datasets for the time span 2007-2012.

(ESA-GOME2)/GOME2

13

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

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

9

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

10

Outlook/Recommendations

Comparisons of NO2 with ground based measurments

Studies on scan angle dpendency should be a part of future operational nadir validation activities.

Thank You