This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 640276.
G2.18 Better agreement needed on systematic and random components of the uncertainty in FTIR measurements and how to evaluate them
Submitted by Anna Mikalsen on 12 June, 2017 - 10:45
Gap abstract:
There is no clear agreement yet within the FTIR community on the distinction and characterisation of the random and systematic components of the uncertainty in FTIR measurements. As a consequence, no common approach is available on how to evaluate these components appropriately leading to a degree of heterogeneity in the global FTIR network.
Part I Gap description
Primary gap type:
- Knowledge of uncertainty budget and calibration
Secondary gap type:
- Technical (missing tools, formats etc.)
ECVs impacted:
- Water vapour
- Ozone
- Aerosols
- Carbon Dioxide
- Methane
User category/Application area impacted:
- Operational services and service development (meteorological services, environmental services, Copernicus Climate Change Service (C3S) and Atmospheric Monitoring Service (CAMS), operational data assimilation development, etc.)
- International (collaborative) frameworks and bodies (space agencies, EU institutions, WMO programmes/frameworks etc.)
- Climate research (research groups working on development, validation and improvement of ECV Climate Data Records)
Non-satellite instrument techniques involved:
- FTIR
-
All these gaps deal with the characterisation of the data quality of FTIR. Thus, they should all be considered at the same time as or prior to the resolution of the current gap.
Detailed description:
Within the NDACC FTIR working group, the technical implementation of the uncertainty propagation (both random and systematic) is fully achieved within the EU QA4ECV and GAIA-CLIM projects. However, each PI must determine a good estimate of site-specific uncertainties on the parameters used as input to the retrieval setup. During the QA4ECV and GAIA-CLIM projects, it was observed that there is not full agreement within the FTIR working group on how the estimation of random and systematic uncertainties for these input parameters should be done. Also, there is no full agreement across the two main retrieval software packages SFIT4 and PROFFIT. Random and systematic uncertainty sources are often assumed differently for different sites/different retrieval software. Although the current data products generated during the QA4ECV and GAIA-CLIM projects are highly harmonzied across participating sites, the network will benefit from a further harmonisation of the uncertainty source assumption. A clear distinction between systematic and random uncertainties implemented network-wide, is important for determining accuracy and precision, e.g. when comparing to satellite data, and uncertainty of an average of data.
Operational space missions or space instruments impacted:
- Independent of specific space mission or space instruments
Validation aspects addressed:
- Geophysical product (Level 2 product)
Gap status after GAIA-CLIM:
- GAIA-CLIM has partly closed this gap
Recipes to evaluate random and systematic parts of the uncertainty sources will be promoted, but that does not mean yet that they will be implemented at each FTIR site by the end of GAIA-CLIM.
Part II Benefits to resolution and risks to non-resolution
| Identified benefit | User category/Application area benefitted | Probability of benefit being realised | Impacts |
|---|---|---|---|
Traceable and consistent error characterization of the FTIR data products |
|
| The agreement on the input data for the uncertainty calculations will assure that the error estimations are consistently traceable and comparable between different sites. |
| Identified risk | User category/Application area at risk | Probability of risk being realised | Impacts |
|---|---|---|---|
Incomparable uncertainty budgets for different sites within NDACC. |
|
| Difficulty of a network-wide and consistent data usage by downstream applications that require network homogeneity. |
Part III Gap remedies
Gap remedies:
Remedy 1: Improved traceability of uncertainties in FTIR measurements
Primary gap remedy type:
Technical
Secondary gap remedy type:
Education/Training
Proposed remedy description:
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 software packages.
Further, a recipe should be developed as to how a random and systematic uncertainty should be determined for each of the leading uncertainty contributions and this recipe should be promoted and implemented in both retrieval software packages at all NDACC FTIR sites. Ideally a centralized QC system or processing will remedy the online publication of FTIR data whose uncertainty budgets is not compliant with the proposed guidelines.
Relevance:
Improved traceability of errors is a core objective of GAIA-CLIM. Traceable ILS uncertainty will allow a traceable estimation of the FTIR product uncertainty due to ILS uncertainties.
Measurable outcome of success:
Comparable and consistently traceable errors for all different sites.
Expected viability for the outcome of success:
- High
Scale of work:
- Consortium
Time bound to remedy:
- Less than 1 year
Indicative cost estimate (investment):
- Low cost (< 1 million)
Indicative cost estimate (exploitation):
- No
Potential actors:
- Academia, individual research institutes