Calibration and Validation of the Jason-2/OSTM Advanced Microwave Radiometer Using Terrestrial GPS Stations

We use estimates of zenith tropospheric delay from terrestrial Global Positioning System (GPS) stations to validate the wet path-delay measurements from the Jason-2/Ocean Surface Topography Mission (OSTM) Advanced Microwave Radiometer (AMR). We validate the AMR wet path-delay measurements provided in the version “T” Geophysical Data Records (GDRs) and those generated using a recently developed coastal algorithm that will be applied to the version “C” GDRs. The new coastal algorithm reduces the variance of the GPS-AMR differences by as much as 28% within 25 km of land. This algorithm also facilitates open-ocean measurement accuracies as close to land as 15 km (as opposed to 25 km). We perform AMR/GPS comparisons with three different troposphere-mapping functions for the GPS-based estimates: Niell, Global, and Vienna. The choice of mapping function has minimal impact on our results, although the Vienna mapping function provided the smallest variance in the AMR–GPS differences.