Potential for High Resolution Wet Path Delay Measurements using High Frequency Radiometers on Future Altimetry Missions
Event: 2014 Ocean Surface Topography Science Team Meeting
Session: Instrument Processing: Corrections
Presentation type: Type Oral
Contribution: PDF file
The next generation of altimeter measurement systems is likely to feature high resolution altimetric observations from SAR and InSAR systems. This enables new science applications in the coastal region, including estuaries and over inland water bodies such as lakes and rivers. But, the heritage 18-37 GHz microwave radiometer systems which provide the important wet tropospheric path delay correction do not provide valid retrievals close to the coast or over land. This paper studies the potential for higher frequency radiometers to fill this gap. Operating at higher frequencies gives improved spatial resolution for the same antenna size which will aid in retrievals near the coast. Additionally, operating near the strong 183 GHz water vapor absorption line enables measurements over all surface types, since the absorption line is strong enough to obscure the surface. Because the retrieval problem is highly non-linear at frequencies above 90 GHz, a different retrieval algorithm approach must be considered from what is typically used for the lower-frequency systems. Simulated data is generated using a radiative transfer model and a notional instrument design. The retrieval accuracy of a neural network and 1-D variational retrieval algorithm are estimated using the simulated data. The results of these performance simulations will be presented along with recommended operating frequencies for the high frequency system.