G4.10

G4.10   Estimates of uncertainties in land surface infrared emissivity atlases.

Gap detailed description

Land surface emissivity atlases in the infrared region (2-16 μm) are required for the validation of infrared satellite sounding measurements over land.  Work is underway, outside of the GAIA-CLIM project, to develop dynamic atlases of spectral emissivity in this part of the spectrum, based on measurements from polar-orbiting hyper-spectral infrared observations and using a rapidly updating Kalman Filter, however these new dynamic atlases need to be validated to ensure the estimates have robust uncertainties associated with them.

Activities within GAIA-CLIM related to this gap

None.

Gap remedy

Remedy #1

·     Establishing dynamic atlases of land surface spectral emissivity in the mid-infrared, utilising observations from hyper-spectral infrared instruments (e.g. IASI) on polar orbiting satellites.

·         Conducting intercomparisons of land surface emissivity atlases.

·       Airborne measurements, using traceably calibrated radiometers, of land surface emissivity in the mid-infrared.

Specific remedy proposed

·         Establish dynamic land surface infrared emissivity atlases.

·         Inter-comparison of available emissivity models.

·         Airborne campaigns to validate land emissivity models in the region (10-250 GHz)

Measurable outcome of success

Publicly available, open-source, dynamic (daily) spectral emissivity atlases in the infrared (2.5-16 μm). Documented, quantitative, evaluation of infrared land surface emissivity atlases and models with respect to measurements of land surface emissivity obtained during airborne campaigns, for a globally representative range of surfaces. Peer reviewed.

Achievable outcomes

Technological / organizational viability: Medium.  Spectral emissivity in the IR is now derived from hyper-spectral IR sounders continuously and in near-real time at the Met Office, as part of the operational NWP system.  Work is underway to incorporate such estimates into a dynamically updated atlas using a Kalman filter and to make this publically available.  This is expected to be achieved by the end of 2017.   The facilities to carry out airborne campaigns exist in Europe (Met Office FAAM aircraft) and costs are typically €250K per three week campaign.

Indicative cost estimate: medium (>1 million Euros)

Relevance

The solution proposed here is fully aligned with the requirement (to establish traceable uncertainties for NWP fields and radiances calculated from them).

Timebound

These remedies are longer-term aspirations, that could be completed in a 2-5 year timescale, resources permitting.

Gap risks to non-resolution