Cell measurements carried out to characterize FTIR instrument line shape (ILS) have their own uncertainties. An ILS retrieval comes along with an uncertainty and an averaging kernel. In particular the averaging kernel for an ILS retrieval is often not adequately considered. For instance, in order to have ILS sensitivity for fine spectral signatures we need very low pressure cells. If the pressure is too high, the cell spectra will not contain information about the ILS at large optical path difference, which is important to understand the fine spectral signatures. This problem is reported by the averaging kernel of the ILS retrieval. Inaccurate knowledge of the ILS leads to larger uncertainties on the retrieved concentrations (XCH4, XCO2).
This gap is not remedied within GAIA-CLIM.
Specific remedy proposed
This can be remedied by requiring that for each ILS retrieval, the averaging kernels are also reported.
Measurable outcome of success
Detailed description of the ILS uncertainties and its influence on the retrieved targets.
Achievable outcomes
Technological / organizational viability: high.
Indicative cost estimate: medium (<1million).
Relevance
The reported uncertainty budgets will be more accurate.
Timebound
2 years
Identified future risk / impact |
Probability of occurrence if gap not remedied |
Downstream impacts on ability to deliver high quality services to science / industry / society |
Underestimation of the uncertainty on the retrieval targets |
high |
Inappropriate confidence assigned to the measurement series leading to erroneous conclusions in downstream applications. |