G2.18    Better agreement needed on systematic versus random part of the uncertainty in FTIR measurements and how to evaluate each part

Gap detailed description

There is no clear agreement yet on what is the systematic part of the uncertainty, and on what the random part of the uncertainty in FTIR measurements is and how to evaluate each part. Random and systematic uncertainty sources are defined differently for the two main retrieval software distributions within the FTIR NDACC working group (PROFFIT and SFIT). To harmonize the uncertainty computation, a recipe should be developed as to how a random and systematic uncertainty should be determined for each of the leading uncertainty contributions in the target retrieval uncertainty budget. The distinction between systematic and random uncertainties is important for determining accuracy and precision, e.g. when comparing to satellite data, and uncertainty of an average of data.

Activities within GAIA-CLIM related to this gap

The uncertainty calculation routines of the SFIT4 retrieval software package has been adapted so that the uncertainty budgets between both PROFFIT and SFIT4 are comparable.

Gap remedy(s)

Remedy #1

Specific remedy proposed

Comparison and tuning of the uncertainty modules of the retrieval software packages. Write down a manual of how to estimate the uncertainties for all parameters that are part of the forward model in the retrieval packages.

Measurable outcome of success

Comparable and consistent errors for all the different sites.

Achievable outcomes

Technological / organizational viability: high

The development is currently ongoing.

Indicative cost: medium (>1 million)


The agreement on the input data for the uncertainty calculations will assure that the error estimations are comparable between different sites.


We are now woeking on reprocessing FTIR CO for QA4ECV, 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

Incomparable uncertainty budgets for different sites on NDACC

High, it occurs right now

Difficulty of a network-wide and consistent data usage 


Work package: