1. Page 1 Envisat Validation Workshop, ACVT-GBMCD, GOMOS altitude-reg. 12/12/2002 Envisat Validation Workshop Atmospheric Chemistry Validation Team Ground-Based Measurements and Campaign Database Subgroup Analysis of GOMOS altitude registration Contribution by AOID 222 Ulrich Blum - University Bonn - blum@physik.uni-bonn.de

2. Page 2 Envisat Validation Workshop, ACVT-GBMCD, GOMOS altitude-reg. 12/12/2002 Data Base GOMOS: - July/August 2002 - 1500 km radius about the Esrange (68 N / 21E) - 56 GOM_NL2__P products from ACRI-server - 22 density/temperature profiles show ungeophysical jumps and in part excessive noise LIDAR: - 18 measurement-runs - relative density profiles (30 - 70 km), i.e. profile shape - absolute temperature profiles (30 - 70 km) GOMOS low-resolution data temperature / K altitude / km

3. Page 3 Envisat Validation Workshop, ACVT-GBMCD, GOMOS altitude-reg. 12/12/2002 Method (1/2) - interpolate Gomos data on lidar altitude-grid - calculate crosscorrelation function (CCF) - use stratopause for CCF calculation (40 - 55 km altitude) - use only data sets with complete overlap (33 data sets) - determine altitude-shift of max. CCF

4. Page 4 Envisat Validation Workshop, ACVT-GBMCD, GOMOS altitude-reg. 12/12/2002 Method (2/2) Crosscorrelation- coefficient : no shift: 0.99 - 1.8 km shift: 0.94 +1.8 km shift: 0.74

5. Page 5 Envisat Validation Workshop, ACVT-GBMCD, GOMOS altitude-reg. 12/12/2002 Results (1/3) Density-data: - logarithm of density - perfect agreement - no altitude shift  note reversed scale

6. Page 6 Envisat Validation Workshop, ACVT-GBMCD, GOMOS altitude-reg. 12/12/2002 Results (2/3) Temperature-data: - scatter in altitude- shift - up and down shifts  note reversed scale

7. Page 7 Envisat Validation Workshop, ACVT-GBMCD, GOMOS altitude-reg. 12/12/2002 Results (3/3) deviations between -1.1 km and +1.7 km mean deviation: -0.2 km large shift: lack of wave signature

8. Page 8 Envisat Validation Workshop, ACVT-GBMCD, GOMOS altitude-reg. 12/12/2002 Large Deviation Case altitude - shift for max. CCF: +1.5 km (Orbit 2252) +1.6 km (Orbit 2253) z  4 km z-resolution < 1.7 km

9. Page 9 Envisat Validation Workshop, ACVT-GBMCD, GOMOS altitude-reg. 12/12/2002 Summary - Comparison of altitude-registration: GOMOS - Lidar - Density data: Perfect agreement - Temperature data: small shift of -200 m (mean) - Large deviations up to  1 km, caused by wave signatures clearly present in Lidar profile lacking in GOMOS profile

10. Page 10 Envisat Validation Workshop, ACVT-GBMCD, GOMOS altitude-reg. 12/12/2002 Further remarks GOMOS low resolution temperature profiles are a composite product of Rayleigh scattering Oxygen concentration a priori model data (ECMWF / MSIS90E) Recommendation: Distribute ONLY that part of the profile, which reflects the GOMOS measurements.