Coastal Performance of Sentinel-6MF New High-Resolution Wet Tropospheric Correction

Abstract

Sentinel-6 Michael Freilich (S6MF) satellite carries the Advanced Microwave Radiometer for Climate (AMR-C), which, in addition to the standard low frequency channels, includes a High-Resolution Microwave Radiometer (HRMR) with channels at 90, 130, and 166 GHz. This subsystem allows higher spatial resolution for enhanced Wet Tropospheric Correction (WTC) measurements in coastal zones. The current S6MF products provide two different WTC fields: AMR WTC, computed from AMR measurements alone, and RAD WTC, computed from the combination of AMR and HRMR. The aim of this study is to evaluate this new high-resolution WTC from S6MF, over the global coastal regions, during the first three years of the mission (2021–2023), in particular to quantify the performance of the RAD WTC when compared with the AMR WTC. Results show that, on average, for distances to coast in the range of 0–5 km, RAD WTC is only available in 13% of S6MF points and an inter-comparison between these two corrections reveals the largest differences for the range of distances to land between 5 and 10 km. Comparisons with ERA5 and global navigation satellite systems (GNSS) reveal that the new RAD WTC is better than the AMR WTC for distances to coast in the range of 5–20 km and, over open-ocean, the current algorithms do not take advantage of the high frequency channels. This evaluation shows how radiometers with high-resolution channels such as the one deployed in S6MF improve the WTC retrieval for 5–20 km from the coast, allowing a higher recovery of accurate sea level measurements in these regions.