Publication: Advancing Mediterranean SST Monitoring: Evaluating the Impact of CIMR on Copernicus SST Products

How can the accuracy and coverage of sea surface temperature monitoring in the Mediterranean be improved? A new study, led by researchers at CNR-ISMAR (Mattia Sabatini, Andrea Pisano, Claudia Fanelli, Bruno Buongiorno Nardelli, Gian Luigi Liberti, Rosalia Santoleri, Craig Donlon-ESA ESTEC, and Daniele Ciani) explores the potentials of the upcoming Copernicus Imaging Microwave Radiometer (CIMR) mission to enhance L4 SST analyses in regional basins.

Why this study? Understanding the Need for CIMR

The aim of this study is to assess the synergy between sea surface temperature (SST) observations from space-based infrared (IR) sensors and the upcoming Copernicus Imaging Microwave Radiometer (CIMR) mission from the European Space Agency, to monitor SST over a regional basin. The approach is applied to the generation of daily gap-free (Level-4, L4) Mediterranean SST maps, produced by CNR-ISMAR within the Copernicus Marine Service SST Thematic Assembly Center. Current maps rely solely on several satellite thermal infrared missions, which are highly accurate and have good spatial resolution (up to ~1 km) but are not able to retrieve SST in cloudy regions. Data gaps are filled using an optimal interpolation (OI) scheme.

The addition of passive microwave (PMW) observations, which are of lower spatial resolution but capable of penetrating cloudiness, would add spatiotemporal coverage, raise the accuracy of L4 SST, and improve the resolution of ocean mesoscale details. This study evaluates the potential benefit of including ESA CIMR mission synthetic PMW observations, launching in 2029. CIMR will provide PMW SST estimates at an unprecedented spatial resolution of ~15 km with near global daily coverage, providing a great opportunity to enhance regional SST products.

What’s New? The First L4 Products Combining IR-PMW SSTs for the Mediterranean

The study opens the door to future generation L4 SST analysis for the Mediterranean Sea in the Copernicus Marine Service, and is the first attempt at building L4 products combining IR and PMW SSTs for the Mediterranean Region. The study is based on an observing system simulation experiment (OSSE), where numerical model outputs are employed to simulate IR, and PMW SSTs and ground truth for assessing the quality of the L4 reconstruction.

What’s the Impact? Improved SST Analysis and Retrieval of SST Frontal Features

The inclusion of CIMR data in the OI algorithm reduced both the mean error and root mean square error (RMSE) of the SST analysis, including the improved retrieval of SST frontal features under severe cloud cover conditions. Improvements are significant even during summer conditions, particularly in areas characterized by strong SST contrast as in presence of coastal upwelling and in correspondence of persistent structures as the Atlantic water inflow in the Alboran Sea, with improvements ranging from 16% to 29% with respect to standard IR-based L4 analysis.

The Long-Term Potential: Advancing SST Monitoring and Impact Prediction

After operational deployment, CIMR will provide new information to improve the Mediterranean L4 SST products within the Copernicus Marine Service, more accurately describing oceanic processes on all scales. In the long run, this can be utilized to contribute towards an improvement in our understanding of ocean/air-sea interaction processes, climate change and the capacity to predict their impact on marine ecosystems.

What’s Next? Preparing for CIMR

The combination of IR and PMW satellite SSTs is currently being implemented to the Copernicus L4 SST Mediterranean and Baltic Sea analyses. This is the first experiment using present-day PMW SSTs from the Advanced Microwave Scanning Radiometer 2, and is important for the exploitation of future high-resolution PMW SST from the CIMR mission.

Read the full publication on Remote Sensing to learn more.

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