Atmosphere Ocean Science Friday Seminar

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Reconstructing velocities from sea surface height measurement: Accounting for noise and ageostrophic effects

Speaker: Ryan Shìjié Dù

Location: Warren Weaver Hall 1314

Date: Friday, October 4, 2024, 4 p.m.

Synopsis:

A central challenge to utilizing the new SWOT data is how to obtain high-resolution sea surface velocity from its measurements of sea surface height (SSH). Early results indicate that SWOT is observing true submesoscale features, at scales where geostrophic balance is no longer accurate. Here we introduce a physics-based reconstruction method that extends the popular effective SQG (eSQG) method to the next order in Rossby number (eSQG+1). Previous work has shown that the SQG+1 model can capture order one flow Rossby number, with realistic vorticity asymmetry and surface convergence on the same magnitude as f. It also effortlessly includes  cyclogeostrophic balance, which has been shown to improve surface velocity reconstruction. For reconstruction, we frame fitting the SQG+1 model SSH to data in a Bayesian inverse problem framework, incorporating expected priors on the SSH spectra, pollution of the balanced signal by the SWOT instrument error (and eventually missing physics like waves).