1. The inter-comparison of SCIAMACHY and radar cloud top heights Alexander A. Kokhanovsky(1), C. Naud(2), A. Devasthale(3) (1)Institute of Remote Sensing, Bremen University Bremen, Germany (2) NASA GISS, New York, USA (3) Max Planck Institute for Meteorology, Hamburg, Germany alexk@iup.physik.uni-bremen.de

2. CONTENTS 1.Rationale 2.Cloud retrievals using SACURA: the accuracy of the forward model 3.Inter-comparison study 4.Conclusions

3. Rationale: The validation of satellite-derived cloud top heights is needed to establish the accuracy of a given technique for the CTH determination. This can be done either using highly accurate lidar or radar systems in space or on ground.

4. CLOUD RETRIEVALS USING SACURA: THE ACCURACY OF THE FORWARD MODEL and the physical principles behind retrievals

5. The cloud optical thickness determination: the physical principle Symbols-SCIATRAN

6. The effective radius determination from a satellite

7. The cloud top height determination from a satellite The physical principle behind the retrieval

8. Preliminary results ! Teh cloud geometrical thickness/bottom height determination from a satellite

9. Inter-comparisons 36.6N; 97.5W

10. Radar: 35-GHz Millimeter wave Cloud Radar 36.6N; 97.5W ARM (USA): 25min 0.5deg

11. Low clouds scia CF radar

12. Low clouds CF scia radar

13. High Clouds

15. The inter-comparisons of CTHs derived using SCIAMACHY, MODIS, and MERIS radar satellite

16. Table 1. Cloud top heights (in km) of low-level clouds derived from radar and satellite data Date(d/m/year)RadarSCIAMERISMODIS 10/03/20031.731.462.211.37 28/03/20032.041.452.012.91 22/05/20031.731.452.502.09 06/11/20031.321.441.71- 16/11/20031.371.450.73- 10/06/20041.862.301.61- 26/ 04/20071.461.453.12- Table 2. Cloud top heights (in km) of high-level clouds derived from radar and satellite data Date(d/m/year)RadarSCIAMERISMODIS 17/04/200311.6614.545.31- 15/05/200311.54 9.355.2010.39 04/06/200310.6012.315.10- 31/10/200313.2011.876.6111.32 12/11/2003 9.56 9.826.928.35 13/11/200310.64 8.096.919.51 22/11/200411.04 8.276.64- Table 1. Cloud top heights (in km) of low-level clouds derived from radar and satellite data

17. Statistical data: average CTH (km) RadarSCIAMERISMODIS Low- level clouds 1.641.571.982.12 High- level clouds 10.4610.06.109.89

18. Conclusions The max error of the cloud top height retrievals for low clouds (below 2km) is in the range [-0.5km; 0.5km] The max error for high clouds(10-12km) is in the range [-3km;+3km].

19. Acknowledgements J. P. Burrows W. von Hoyningen-Huene V. V. Rozanov, H. Bovensmann, M. Vountas, W. Lotz ESA, DLR