Sensitivity of Low-Elevation Coherent GNSS Reflections to the Planetary Boundary Layer Refractivity

Analysis of GNSS radio occultation (RO) data has shown clear detection of coherent reflections off the surface of the Earth, especially over oceans and ice. Previous studies have yielded initial evidence that these reflected events can be sensitive to surface parameters and near-surface atmospheric conditions. In this study, we perform simulations of GNSS RO reflections under a range of atmospheric conditions. In particular, we focus on the regions over subtropical Eastern oceans where ducting conditions are known to be prevalent. It is known that under ducting conditions, the inversion of bending angles to refractivity is no longer unique. Thus we investigate whether reflections observed from RO can be utilized as a constraint to the inversion of the occultation signal. Improvements of RO retrieval near the surface will have significant values in the remote sensing of the planetary boundary layer.