Exploring the potential of Sentinel-3 fully-focused SAR altimeter range data for enhanced detection of coastal currents along the Northwestern Atlantic Shelf

Hui Feng (University of New Hampshire, United States)

CoAuthors

Alejandro Egido (NOAA – Laboratory for Satellite Altimetry, United States); Doug Vandemark (University of New Hampshire, United States)

Event: 2019 Ocean Surface Topography Science Team Meeting

Session: Instrument Processing: Measurement and Retracking

Presentation type: Type Poster

Fully-focused Synthetic Aperture Radar (FF-SAR) is a novel SAR altimetry data processing technique that accounts for the phase evolution of the targets in the scene, making it possible to focus the complex echoes along the aperture. The process combines coherently all the available radar returns on the surface to improve the resolution and measurement precision, and can potentially reduce the along-track resolution to its theoretical limit equal to L/2, where L is the antenna length.
Our study in the OSTST-2018 presented a preliminary assessment of the FF-SAR mode range data from Cryosat-2 (CS2) altimetry in the Nova Scotian Shelf (NSS). With the pseudo-low resolution mode (PLRM) data as a baseline, CS2 FF-SAR parameters (range, wave height, sigma0, and range-gradient derived geostrophic current Vg) were examined to demonstrate the improvements of FF-SAR over PLRM, particularly in the detection of nearshore currents in the NSS. Clearly, we found that 1) the noise reduction (i.e. precision improvement) of the FF-SAR data (i.e. range and range-derived current) is apparent and 2) finer-scale signals are identified in the FF-SAR data.
However, the uneven time-space coverage in CS2 SAR mode data in the region limits its further evaluation and application. As a natural continue to the work, we propose to apply the established evaluation strategy to the SAR mode datasets from Sentinel-3A/3B altimeters that by design provide regular time-space coverage along the northwestern atlantic shelf (from the Mid-Atlantic Bight, the Gulf of Maine to Nova Scotia shelf). In the further analysis, the objectives include 1) to explore a more objective cross-shelf length scale to derive along-shelf coastal current Vg, 2) to investigate whether or not geophysical corrections (e.g. tide, DAC, etc. ) should be applied for an improved detection of the NSS coastal currents, and 3) understand what small-scale signals identified in FF-SAR data represent, such as current, internal waves, or just non-geophysical noises. To reach these, past and ongoing in situ hydrographic and current measurements, and modeling datasets in the region will be used to provide expected mean and dynamical circulation features from the shelf break up to the coast.
 

Poster show times:

Room Start Date End Date
The Gallery Tue, Oct 22 2019,16:15 Tue, Oct 22 2019,18:00
The Gallery Thu, Oct 24 2019,14:00 Thu, Oct 24 2019,15:45
Hui Feng
University of New Hampshire
United States
hui.feng@unh.edu