Aerosol optical thickness retrieval over land and water using SCIAMACHY/GOME data

1. J. Kusmierczyk-Michulec G. de Leeuw Aerosol optical thickness retrieval over land and waterusing SCIAMACHY/GOME data

2. The SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY (SCIAMACHY) on board the ESA Envisat satellite • launched in March 2002 • high-resolution (0.2-0.4 nm) spectrometer • wavelength range: 240--2380 nm • Swath Dim.: 960 km (cross track) by • 25 km (along track at nadir) • Nadir scan: 4 pixels of 240 km (cross track) by 25 km (along track) • Limb scan: 960 km (cross track) vertical tangential step size 3.0 km http://envisat.esa.int/ Aerosol optical thickness retrieval

3. The Global Ozone Monitoring Experiment (GOME) • Launched in April 1995 • 4-channel grating spectrometer • Spectral resolution 0.2-0.4 nm • Wavelength range: 240 -790 nm • One across-track : 3 ground pixels: 40 km x 320 km GOME aboard ERS-2 (courtesy of ESA) Aerosol optical thickness retrieval

4. Aerosol retrieval algorithmfor SCIAMACHY/GOME where atm = R + a + aR s is the zenith solar angle is thezenith observation angle s -is the relative azimuth between the incident and observation vertical planes Aerosol optical thickness retrieval

5. TOA reflectance - example • Ra is based on the sunphotometer • measurements in Ispra (03.06.98) • (Holben et al. 1998) • Rtoa - GOME data Aerosol optical thickness retrieval

6. Spectral reflectances of natural surfaces -examples LER-Lambertian Equivalent Reflectance derived from reflectances measured by GOME (R. Koelemeijer et al., 2003) Aerosol optical thickness retrieval

7. Approach over land/water for GOME Reflectances at TOA measured by GOME (380, 440, 463, 495, 555, 670 nm) LUT of aerosol/atmospheric/Rayleigh reflectances for a given satellite and solar geometry 3 predominantly aerosol types -“maritime”, <-0.1, 0.65> - “continental”, <0.65, 1,32> - “urban”, <1.32, 2.8> Cloud screening FRESCO algorithm (Koelemijer et al., 2001,2002) Correction for ozone absorption The best fit with aerosol model Surface correction GOME surface reflectances database AOD Aerosol optical thickness retrieval

8. Validation Aerosol optical thickness retrieval

9. Validation Aerosol optical thickness retrieval

10. Validation Aerosol optical thickness retrieval

11. Validation Aerosol optical thickness retrieval

12. Validation Aerosol optical thickness retrieval

13. Validation Aerosol optical thickness retrieval

14. Validation Aerosol optical thickness retrieval

15. Validation Aerosol optical thickness retrieval

16. Validation Aerosol optical thickness retrieval

17. Aerosol optical thickness, winter 1997 Outline Aerosol optical thickness retrieval

18. Aerosol optical thickness, winter 2000 Aerosol optical thickness retrieval

19. Aerosol optical thickness, summer 1997 Aerosol optical thickness retrieval

20. Aerosol optical thickness, summer 2000 Aerosol optical thickness retrieval

21. Aerosol optical thickness, spring/autumn 1997 Aerosol optical thickness retrieval

22. Aerosol optical thickness, spring/autumn 2000 Aerosol optical thickness retrieval

23. Acknowledgments • We thank the PI investigators: Didier Tanré, Brent Holben, Philippe Goloub and Giuseppe Zibordi, and their staff for establishing and maintaining the AERONET sites used in this investigation. • We acknowledge Piet Stammes and Martin de Graaf for kindly providing us GOME data and the results from FRESCO algorithm. • The algorithm was developed as part of the EO-037 project of the National Data User Support Program of the Netherlands Space Research Organization (SRON). Aerosol optical thickness retrieval

24. Illustration of the retrieval process- example 1 Aerosol optical thickness retrieval

25. Illustration of the retrieval process – example 2 Aerosol optical thickness retrieval

26. Illustration of the retrieval process – example 3 Aerosol optical thickness retrieval

27. Contribution of the surface to TOA reflectance Aerosol optical thickness retrieval