Envisat Validation Workshop Atmospheric Chemistry Validation Team GroundBased
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 Envisat Validation Workshop, ACVT-GBMCD, GOMOS altitude-reg. 12/12/2002 Page 1
GOMOS low-resolution data Data Base - July/August 2002 - 1500 km radius about the Esrange (68 N / 21 E) - 56 GOM_NL 2__P products from ACRI-server - 22 density/temperature profiles show ungeophysical jumps and in part excessive noise LIDAR: altitude / km GOMOS: - 18 measurement-runs - relative density profiles (30 - 70 km), i. e. profile shape - absolute temperature profiles (30 - 70 km) temperature / K Envisat Validation Workshop, ACVT-GBMCD, GOMOS altitude-reg. 12/12/2002 Page 2
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 Envisat Validation Workshop, ACVT-GBMCD, GOMOS altitude-reg. 12/12/2002 Page 3
Method (2/2) Crosscorrelationcoefficient : no shift: 0. 99 - 1. 8 km shift: 0. 94 +1. 8 km shift: 0. 74 Envisat Validation Workshop, ACVT-GBMCD, GOMOS altitude-reg. 12/12/2002 Page 4
Results (1/3) Density-data: - logarithm of density - perfect agreement - no altitude shift note reversed scale Envisat Validation Workshop, ACVT-GBMCD, GOMOS altitude-reg. 12/12/2002 Page 5
Results (2/3) Temperature-data: - scatter in altitudeshift - up and down shifts note reversed scale Envisat Validation Workshop, ACVT-GBMCD, GOMOS altitude-reg. 12/12/2002 Page 6
Results (3/3) deviations between -1. 1 km and +1. 7 km mean deviation: -0. 2 km large shift: lack of wave signature Envisat Validation Workshop, ACVT-GBMCD, GOMOS altitude-reg. 12/12/2002 Page 7
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 Envisat Validation Workshop, ACVT-GBMCD, GOMOS altitude-reg. 12/12/2002 Page 8
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 Envisat Validation Workshop, ACVT-GBMCD, GOMOS altitude-reg. 12/12/2002 Page 9
Further remarks GOMOS low resolution temperature profiles are a composite product of • Rayleigh scattering • Oxygen concentration • a priori model data (ECMWF / MSIS 90 E) Recommendation: Distribute ONLY that part of the profile, which reflects the GOMOS measurements. Envisat Validation Workshop, ACVT-GBMCD, GOMOS altitude-reg. 12/12/2002 Page 10
- Slides: 10