G2.20   Too large spectroscopic uncertainties in FTIR H2O and CH4 products

Gap detailed description

The current spectroscopic databases contain too large uncertainties to model correctly the spectral windows used for H2O and CH4 retrievals. Meanwhile, the FTIR instruments (ground- and space-based high resolution spectrometers) are of such high quality that they cannot only reveal inconsistencies between the parameters of different lines but also of insufficient line shape parameterisations (Voigt line shape, speed dependent Voigt line shape, etc.). This gap causes an increase in the uncertainty on the delivered H2O and CH4 products retrieved from high resolution and high quality measurements.

Activities within GAIA-CLIM related to this gap

This gap is not addressed within GAIA-CLIM.

Gap remedy(s)

Remedy #1

Specific remedy proposed

Perform and analyse spectroscopic experiments in the laboratory in the spectral bands used for ground-based and satellite retrievals. Use the high quality atmospheric spectra for indentifying uncertainties in the parameterisation of the line shape and for constraining the uncertainties of the line parameters.

Measurable outcome of success

Updated spectroscopic databases that have better demonstrated quality and following this, an improvement in the uncertainty budegt of the FTIR
H2O and CH4 products.

Technological / organizational viability: high.

Indicative cost estimate: medium (< 1 million).


If the spectroscopic databases could be updated and improved accordingly to model correctly the spectral windows used for H2O and CH4 retrievals, this would demonstrably improve the data quality of the delivered H2O and CH4 products retrieved from otherwise high quality measurements.


3 years.

Gap risks to non-resolution

Identified future risk / impact

Probability of occurrence if gap not remedied

Downstream impacts on ability to deliver high quality services to science / industry / society

Errors on the retrieved product. These errors will increase the higher the quality of the measured spectra.

It occurs right now and will become even more important in the future.

Erroneous data products leading to incorrect inferences by users and limiting applicability for downstream applications.


Work package: