Acknowledgements : R. Bevilacqua and NRL POAM III Science Team Validation of ENVISAT Products using POAM III O3, NO2, H2O and O2 profiles Authors: F. GOUTAIL, A. BAZUREAU Description of POAM instrument Constituents measured List of profiles available Example of Profiles Comparison with GOMOS Conclusion Acknowledgements : R. Bevilacqua and NRL POAM III Science Team  

Description of POAM III Instrument Launched on SPOT 4 satellite (CNES) on March 1998 Heliosynchronous quasi-polar orbit : HN (sunrise) – HS (sunset) 14 profiles/ day in each hemisphere (at the same latitude) Between 54 – 71 °N Between 62 - 87 °S Solar occultation technique in UV- visible band Vertical profiles of O3, NO2, H2O, O2 Vertical resolution 1 km for O3 1.5 to 2.5 km for NO2 HN varying with season HS

POAM III Validation results

List of profiles available Since July 2002 Monthly “package” for each hemisphere from July to November 2002. Profiles of O3, NO2, H2O, O2 and aerosol extinction coefficient at 1018 nm Profiles of Pressure and Temperature from NMC analysis Very soon : December POAM III profiles Future developments : all aerosol extinction coefficient profiles and … all errors bars (for all constituents) - POAM III HDF data Version 2 -

Example of profiles POAM III and GOMOS

Comparisons with GOMOS : Southern Hemisphere - July 2002 Coincidence criterions : time < 24 hours distances < 800 km 20 “matches” found : 13 25Eta Tau (2.8) 7 87Alp Tau (0.8)

Comparisons with GOMOS : Southern Hemisphere - July 2002 Pressure and temperature profiles : NMC analysis versus ECMWF Analysis conducted for each star

Comparisons with GOMOS : Southern Hemisphere - July 2002 Constituents profiles comparisons :

Comparisons with GOMOS : Southern Hemisphere - July 2002 Constituents profiles comparisons :

Comparisons with GOMOS : Northern Hemisphere - September 2002 on work Coincidence criterions : time < 24 hours distances < 800 km 47 “matches” found 49 Del Cap (2.8) 20 distances GOMOS / POAM III < 400 km

Comparisons with GOMOS : Northern Hemisphere - September 2002 Pressure and temperature profiles : NMC analysis versus ECMWF model

Comparisons with GOMOS : Northern Hemisphere - September 2002 Constituents profiles comparisons :

Comparisons POAM III / GOMOS : SUMMARY Comparisons of pressure and temperature relative difference profiles for each star :

Comparisons POAM III / GOMOS : SUMMARY (2)

Conclusions Comparison and validation programs are now ready for ENVISAT instruments validation Reading PDS format programs not yet well mastered (several problems with Enviview) Extraction of ENVISAT instrument profiles still hard working … Waiting for GOMOS aerosol extinction coefficients profiles Waiting for new GOMOS processing for O3, O2, NO2, H2O MIPAS profiles coincident with POAM III available ? First SCIAMACHY profiles are waited in January 2003