Sea ice monthly surface emissivity at 23.8 GHz, calculated using AMSU-A brightness temperatures through the inversion of the radiative transfer equation. The atmospheric components and surface temperature are from the ARPEGE analyses for January, 2009.
The main objective of our investigation will be to improve the quality of the wet tropospheric correction for the current and future altimetry missions. The rather long history of spaceborne microwave radiometers associated to altimeters (ERS-1/2, Topex/Poseidon, Envisat, Jason-1/2) has given a good maturity to methods used for in-flight calibration and data inversion over open ocean. However, since the beginning of altimeter missions, the overall objective of these missions has been progressively widened, and demands for better accuracy, resolution and stability have increased. It is therefore necessary to revisit the data processing strategy, in order to fulfil these new objectives.
More specifically, we intend to address both the data quality (relative and absolute calibration) for applications in climate studies, and inversion approaches, with a view, at more or less long term, to develop a single tool for estimating the wet tropospheric correction for all types of surfaces (ocean, coastal areas, inland waters, polar ice).
In the following, we present the proposed study in three work packages:
- in flight calibration: application of state-of-the-art methods to assess and possibly correct for any calibration anomaly after launch, and along the mission life time
- long term monitoring, multi-mission calibration, minimization of the absolute calibration error
- strategy for the wet tropospheric correction estimation using radiometric data over various or mixed surfaces (ocean, coasts, inland waters and possibly polar ice)