WP4: Observations from ground networks

Work package 4 OBSERVATIONS FROM GROUND NETWORKS

Remote sensing Measurement of the modification of the solar radiation by the atmosphere

Wellenlänge (  m) N2ON2O N2ON2O O3O3 O3O3 O3O3 O3O3 wavenumber (cm -1 ) wavelength (  m) intensity (arb. Units)

Activities: -Perform solar absorption measurements in the mid-infrared spectral region at the 7 European NDACC stations spanning latitudes from 28°N to 80°N, throughout the duration of the project, at a minimal frequency of about 1 meas./week -Perform solar absorption measurements at Ile de La Réunion during a 3-months campaign -Optimise the retrieval of CH 4 in the mid-infrared spectral region -Evaluate the error budget of CH 4 and N 2 O vertical profile data -Provide a consistent set of total column densities and vertical profiles of CH 4 and N 2 O for model evaluation and satellite validation -Validate and calibrate the SCIAMACHY and infrared satellite measurements

Heritage of UFTIR ( , coordinator: BIRA, Martine deMaziere) UFTIR: EC project including all European FTIR partners that are also in HYMN, as well as Univ. Oslo

Objectives of UFTIR:  Establish common strategy for retrieval and characterisation of the vertical distributions of the target gases from FTIR ground-based measurements - optimise retrieval for each target gas.  Re-analysis of existing time series for evaluation of trends and associated uncertainties in troposphere (and stratosphere); a bootstrap resampling method has been used for trend analysis  Integrate burdens and trend data in tropospheric model assessments - to improve models and verify consistencies with known emissions; the model used is the Oslo 3D model ‘CTM2’ of Univ. Oslo The target molecules were CO, O 3, C 2 H 6, HCFC-22, N 2 O and CH 4

Example: UFTIR settings for CH 4 retrieval:  Retrieval in 5 microwindows simultaneously : cm -1 ; cm -1 ; cm -1 ; cm -1 ; cm -1.  Interfering species: HDO, N 2 O, CO 2  DoF  3  Relative error on tropo- column  10% !! BUT spectroscopy problems : inconsistencies are found between different microwindows, affecting the retrieved profile shapes

Trend of tropospheric and stratospheric column abundances wrt 2000? Significantly positive: ranges from (0.1  0.05 )%/yr to (0.6  0.1 )%/yr ; except for tropo- column at Izana: (±0.09) )%/yr reasonably good agreement with UiO 3D model simulations Seasonal variation is obvious Consistent data sets; possibly not optimal yet... UFTIR data set for CH 4 (total column) :

UFTIR settings for N 2 O retrieval  DoF  4.5  relative error on tropospheric column  %

UFTIR data set for N 2 O (total column) Trend: significantly positive, in agreement with the surface trend of +(0.25  0.05) %/yr reported in IPCC 2003 based on in-situ observations

Current situation for CH 4 :  UFTIR: Optimal microwindows determined for profile retrieval  Total column precision: Near-IR: < 0.5 % (reference gas O 2 ) (Washenfelder et al, 2003) Mid-IR: 0.5% achievable, but not thoroughly investigated  Tropospheric column: Near-IR: < 0.5 % using HF (Washenfelder et al, 2003) Mid-IR: ~ % (UFTIR), use of HF ?  No consistent dataset available  Lack of measurements and validation in the tropics  Accuracy ? To be done in HYMN: Continuation of measurements at the European NDACC sites Performing measurement campaigns in the tropics Optimisation of the total column retrieval of CH 4 in the mid-IR Evaluation of the error budget of vertical profile data (CH 4 and N 2 O) Provision of a consistent set of total column densities and vertical profiles of CH 4 and N 2 O for model evaluation and satellite validation. Validation of the SCIAMACHY and IASI satellite measurements.