Articles | Volume 13, issue 2
Research article
29 Mar 2017
Research article |  | 29 Mar 2017

On the mesoscale monitoring capability of Argo floats in the Mediterranean Sea

Antonio Sánchez-Román, Simón Ruiz, Ananda Pascual, Baptiste Mourre, and Stéphanie Guinehut

Abstract. In this work a simplified observing system simulation experiment (OSSE) approach is used to investigate which Argo design sampling in the Mediterranean Sea would be necessary to properly capture the mesoscale dynamics in this basin. The monitoring of the mesoscale features is not an initial objective of the Argo network. However, it is an interesting question from the perspective of future network extensions in order to improve the ocean state estimates. The true field used to conduct the OSSEs is provided by a specific altimetry-gridded merged product for the Mediterranean Sea. Synthetic observations were obtained by sub-sampling this Nature Run according to different configurations of the ARGO network. The observation errors required to perform the OSSEs were obtained through the comparison of sea level anomalies (SLAs) from altimetry and dynamic height anomalies (DHAs) computed from the real in situ Argo network. This analysis also contributes to validate satellite SLAs with an increased confidence. The simulation experiments show that a configuration similar to the current Argo array in the Mediterranean (with a spatial resolution of 2°  ×  2°) is only able to recover the large-scale signals of the basin. Increasing the spatial resolution to nearly 75 km  ×  75 km, allows the capture of most of the mesoscale signal in the basin and to retrieve the SLA field with a RMSE of 3 cm for spatial scales larger than 150 km, similar to those presently captured by the altimetry. This would represent a theoretical reduction of 40 % of the actual RMSE. Such a high-resolution Argo array composed of around 450 floats, cycling every 10 days, is expected to increase the actual network cost by approximately a factor of 6.

Short summary
In this work we investigate the capability of the Argo array in the Mediterranean Sea to capture mesoscale circulation structures (diameter of around 150 km). To do that we conduct several experiments to simulate different spatial sampling configurations of the Argo array in the basin. Results show that the actual Argo array in the Mediterranean (2° × 2°) might be enlarged until a spatial resolution of nearly 75 × 75 km (450 floats) in order to capture the mesoscale signal.