G1.09 Limited availability of quantitative CO profiles

Gap detailed description

Assess gaps in the observation system for CO vertical profiles and their impact on the evaluation of models and the derivation of top-down CO emissions. Source inversion techniques will help to evaluate how ground-based measurements can provide useful constraints in the derivation of top-down estimates for CO sources and sinks on the global scale. The impact of improved vertical resolution on the inversion of emissions, i.e. on posterior flux uncertainties and on the ability of the system to differentiate between different emission sources, will be determined. 

Activities within GAIA-CLIM related to this gap

Methyl chloroform-derived constraints on OH fields from the recent literature will be used, and based on their uncertainties we shall perform sensitivity source inversions using either MOPITT or IASI CO retrievals. Vertical CO profile measurements by ground-based FTIR instruments are used as additional constraints in the source optimizations, since vertical concentration gradients reflect the effects of chemical sinks. Vertical FTIR data are scarce, but better characterized than vertical information from satellites. The main outcomes will be (1) an updated top-down determination of CO emissions and photochemical productions, (2) an assessment of the sensitivity of the top-down emissions to errors in [OH] as well as other model parameters, and (3) a determination of the added value represented by vertical CO profiles at FTIR stations. These analyses will start in November 2016 and shall be the subject of a deliverable due in M34.

Gap remedy(s)

Remedy

Specific remedy proposed

Within GAIA-CLIM, the existing scarce quantitative vertical profiles of CO will be used to quantify their added value and to determine the potential benefits of additional data collection. If the existing data are found insufficient, the likely remedy would consist in the retrieval of FTIR vertical profiles from an additional 5-10 well distributed stations over a period of several years, with at least 1-2 stations per 30 degree latitude band between the North and the South Pole. 

Measurable outcome of success

Success would be if it is shown that the use of vertical CO profiles at FTIR stations and in situ observations from surface networks (e.g. GMD, GAW) provides a measurable added value to the top-down emission estimates of CO derived by inversion of satellite observations. This approach will then be adopted and specific recommendations will be provided to the EO community regarding its scientific, and technological benefits.

Achievable outcomes

Technological / organizational viability: Medium. From the technological point of view the undertaking is entirely feasible. The scientific results will have to be presented and discussed through open dissemination and two-way interactions with the EO community, in order to ensure the involvement of potentially interested actors outside the GAIA-CLIM community.

Indicative cost estimate: Difficult to estimate, but most likely higher than 1 million.

Relevance

This approach should help to ensure better use of observations for the derivation of CO budget on the global scale. It should also indicate future directions for a possible extension of the observational network for CO.

Timebound

The sensitivity analyses will be performed and completed within the framework of the GAIA-CLIM project. A peer-review publication, summarizing the approach and the results, is also planned before the end of the project. The remedy to the gap will require at least several years before sufficient data are obtained.

Gap risks to non-resolution