The Harmony scientific workbench part 1

Abstract

This article introduces the Harmony scientific workbench (SWB), a tool for modelling the multistatic, polarimetric ocean observations of the European Space Agency (ESA) Earth Explorer 10 Harmony mission. This work focuses on the simulation of the level-1 (L1) radar observations of the ocean that the mission is expected to produce. These L1 products, along with their modeled errors and uncertainties, are used as input for testing level-2 (L2) retrieval algorithms which invert the radar observables to geophysical variables, such as stress-equivalent wind at 10 m height (U10s) and total surface current (TSC). The L2 retrieval is documented in a companion paper [1]. For Harmony’s L1 normalized radar cross-section (NRCS) and Doppler observations, we extend the Radar Imaging Model (RIM) and Doppler Radar Imaging Model (DopRIM) to account for bistatic geometry and polarimetry. Our implemented forward model relies on wave spectra that are locally altered by wind variations and surface currents. Additionally, cutoff wavelengths and mean cross-section (MACS) are estimated from synthetic aperture radar (SAR) spectra, which are computed using a bistatic mapping function that accounts for polarimetry. The forward models are applied to two ocean scenes to demonstrate the effect of local current and wind-speed variations on the observations. We validate our simulated outputs by comparing against existing C-band geophysical model functions (GMFs). By implementing the RIM, DopRIM and bistatic spectral transfer functions in a consistent manner, this work represents the most complete treatment of the multiscale nature of high-resolution SAR ocean observations to date.