1. thomas.wagner@mpch-mainz.mpg.de Satellite group MPI Mainz Investigating Global Long-term Data Sets of the Atmospheric H 2 O VCD and of Cloud Properties T. Wagner 1, S Beirle 1, M. Grzegorski 1, M. Penning de Vries 1, U. Platt 2 (1)MPI für Chemie, Mainz, Germany (2)Institut für Umweltphysik, University of Heidelberg, Germany What can new satellite observations offer? (spectral measurements) Model results & measurements of O 4 & O 2 absorption and Ring effect Case studies Conclusions MPI Mainz Germany

2. thomas.wagner@mpch-mainz.mpg.de Satellite group MPI Mainz GOME & SCIA spectral properties Both, trace gas absorptions and Ring effect (Raman scattering) are affected by modifications of the atmospheric light path, especially due to clouds. => They can provide information about the internal cloud structure What additional information can be expected from spectral measurements? (e.g. GOME) O4O4

3. thomas.wagner@mpch-mainz.mpg.de Satellite group MPI Mainz Solar Fraunhofer line in direct and scattered light Ratio spectrum of scattered and direct solar light Optical depth  10% Optical depth  2% The Ring effect is strongest in the UV GOME UVGOME red Ring effect: ‚Filling-in‘ of Fraunhofer lines due to rotational Raman-scattering

4. thomas.wagner@mpch-mainz.mpg.de Satellite group MPI Mainz NOAA GOES-8 Satellite, 16:02 UTC Cloud effects Hurrican Fran, 04.09.1996:

5. thomas.wagner@mpch-mainz.mpg.de Satellite group MPI Mainz Instrument Green points indicate scattering points of photons => reception area of the detector Backward Monte Carlo (TRACY-II, T. Deutschmann ) Tim Deutschmann, IUP Heidelberg Realistic modelling of microscopic and macroscopic cloud properties aerosol layer Instrument aerosol layer Tim Deutschmann, IUP Heidelberg Instrument Strong forward peak aerosol layer Moderate forward peak Suniti Sanghavi, IUP Heidelberg

6. thomas.wagner@mpch-mainz.mpg.de Satellite group MPI Mainz Different dependence for O 2 and O 4 Absorption is expresses as air mass factor (AMF) It is a measure of sensitivity AMF = 1 indicates an absorption corresponding to the vertical atmospheric column Model results as function of cloud altitude:

7. thomas.wagner@mpch-mainz.mpg.de Satellite group MPI Mainz Model results as function of cloud altitude: Ring effect shows monotonous decrease Different dependence for O 2 and O 4 -In general, clouds cause a decrease of the absorptions of O2 and O4 and of the strength of the Ring effect -the Ring effect hardly depends on the surface albedo

8. thomas.wagner@mpch-mainz.mpg.de Satellite group MPI Mainz Dependence of the O2 absorption on cloud fraction and cloud altitude (vertical thickness: 1km,OD: 50) Results for surface albedo of 2%

9. thomas.wagner@mpch-mainz.mpg.de Satellite group MPI Mainz Normalised O2 absorption Derived cloud top height [km] Long time mean 1996-2003 from GOME Wagner et al., 2008

10. thomas.wagner@mpch-mainz.mpg.de Satellite group MPI Mainz Spatial correlation analyses between the GOME and ISCCP data sets (annual average) of effective cloud fraction (red) and cloud amount (blue). After the ISCCP cloud amount is corrected for the effect of changing optical depth, improved agreement with the GOME data is found.

11. thomas.wagner@mpch-mainz.mpg.de Satellite group MPI Mainz Correlation analyses between the GOME and ISCCP data sets (spatial variation of the annual average) of cloud height (red: uncorrected ISCCP top height, blue corrected ISCCP effective cloud top height). After the ISCCP data is corrected for the effect of changing optical depth, improved agreement with the GOME data is found.

12. thomas.wagner@mpch-mainz.mpg.de Satellite group MPI Mainz Correlation between effective cloud top height from FRESCO and derived from our Ring analysis (GOME observations in November 2000 for SZA 19-23°, CF >50%). Depending on the assumed cloud properties in the forward model, different effective cloud top heights are derived from the Ring effect observations.

13. thomas.wagner@mpch-mainz.mpg.de Satellite group MPI Mainz Dundee Satellite Receiving Station, Dundee University, Scotland (http://www.sat.dundee.ac.uk/). Dundee Satellite Receiving Station, Dundee University, Scotland (http://www.sat.dundee.ac.uk/). Special cases: I) Separation of the effects of clouds and snow/ice

14. thomas.wagner@mpch-mainz.mpg.de Satellite group MPI Mainz Typically the shielding effect of clouds is dominant It can be caused by clouds or mountains Special cases: II) Increased absorptions of O2 and O4

15. thomas.wagner@mpch-mainz.mpg.de Satellite group MPI Mainz Sometimes, strongly enhanced absorptions indicate long light paths inside clouds The Ring effect shows no enhancement Special cases: II) Increased absorptions of O2 and O4

16. thomas.wagner@mpch-mainz.mpg.de Satellite group MPI Mainz The cloud is also seen by the microwave measurements (liquid water path)

17. thomas.wagner@mpch-mainz.mpg.de Satellite group MPI Mainz Additional examples of strongly enhanced absorptions (about 10 per month for GOME-1 observations)

18. thomas.wagner@mpch-mainz.mpg.de Satellite group MPI Mainz Modelled Radiance 3-D effects (TRACY-2)

19. thomas.wagner@mpch-mainz.mpg.de Satellite group MPI Mainz Modelled O4 AMF 3-D effects (TRACY-2)

20. thomas.wagner@mpch-mainz.mpg.de Satellite group MPI Mainz Modelled Ring effect 3-D effects (TRACY-2)

21. thomas.wagner@mpch-mainz.mpg.de Satellite group MPI Mainz 1 day of H2O from GOME-1

22. thomas.wagner@mpch-mainz.mpg.de Satellite group MPI Mainz H 2 O SCD derived from GOME-2 for 20.01.2008. Due to the high spatial resolution and almost daily global coverage many details of the atmospheric H 2 O circulation can be seen. 1 day of H2O from GOME-2 (similar results from S. Noel, IUP Bremen)

23. thomas.wagner@mpch-mainz.mpg.de Satellite group MPI Mainz H2O anomalies during ENSO

24. thomas.wagner@mpch-mainz.mpg.de Satellite group MPI Mainz Cloud fraction anomalies during ENSO

25. thomas.wagner@mpch-mainz.mpg.de Satellite group MPI Mainz No Cloud anomalies in time series!

26. thomas.wagner@mpch-mainz.mpg.de Satellite group MPI Mainz Spectral measurements (O 2 & O 4 absorption & Ring effect) are well suited for cloud retrievals Monte-Carlo radiative transfer modelling provides optimum link between observations and macroscopic and microscopic cloud properties; 3-D effects should be considered Ring effect and O 2 /O 4 absorptions are affected by clouds and snow/ice differently Strongly enhanced absorptions found in GOME data (about 10 times per month, especially frequent for narrow swath mode) New H 2 O product from GOME-2 Application to atmospheric studies, e.g. ENSO Conclusions

27. thomas.wagner@mpch-mainz.mpg.de Satellite group MPI Mainz Global average distribution of the Ring effect for November and December 2000 (left: cloud fraction 20%). In areas with high clouds, especially over the continents, the weakest Ring effect is found.