MW / IR intercomparison campaign for the establishment of a SST skin – subskin relation

Short abstract

Temperature rise and the immediate effect it has over the Arctic calls for increased monitoring of sea surface temperature (SST), which demands the highest possible synergy between the different sensors orbiting Earth, both on present and future missions. One example is the possible synergy between Sentinel-3’s SLSTR and the future Copernicus Imaging Microwave Radiometer (CIMR), which is currently in development phase. To achieve that, there is a need to establish a relation between skin and subskin SST, which are measured by infrared and microwave sensors respectively. That could lead to the creation of better datasets that could be assimilated into climate models.

To address the aforementioned issue, the Danish Meteorological Institute (DMI) and the Technical University of Denmark (DTU) did, on June 2021, a week-long intercomparison campaign between Denmark and Iceland, where they collected data by simultaneously deploying microwave and infrared sensors side-by-side. DMI is a part of the International Sea Surface Temperature Fiducial Reference Measurement Radiometer Network (ISFRN) and has experience on shipborne radiometer deployments in the North Sea, and DTU has long experience in microwave radiometer deployment campaigns. In this particular campaign, two ISARs (Infrared Sea Surface Temperature Autonomous Radiometer), measuring on the 9.6 – 11.5 μm spectral band, were deployed alongside two recently refurbished EMIRADs, namely EMIRAD-C and EMIRAD-X, measuring on C and X band respectively. The intercomparison campaign and the corresponding research are funded by ESA as part of the SHIPS4SST Phase 2 project.

This study aims at demonstrating the methodology applied to retrieve SST from the microwave brightness temperature using Optimal Estimation techniques, and present a first attempt to establish a relationship between skin and subskin SST, as well as the overall research progress so far.