For the first time in the Mediterranean Sea various temperature sampling strategies are studied and compared to each other by means of the Observing System Simulation Experiment technique. Their usefulness in the framework of the Mediterranean Forecasting System (MFS) is assessed by quantifying their impact in a Mediterranean General Circula- tion Model in numerical twin experiments via univariate data assimilation of temperature profiles in summer and winter conditions. Data assimilation is performed by means of the optimal interpolation algorithm implemented in the SOFA (System for Ocean Forecasting and Analysis) code.<br />The sampling strategies studied here include various com- binations of eXpendable BathyThermograph (XBT) profiles collected along Volunteer Observing Ship (VOS) tracks, Air- borne XBTs (AXBTs) and sea surface temperatures. The actual sampling strategy adopted in the MFS Pilot Project during the Targeted Operational Period (TOP, winter-spring 2000) is also studied.<br />The data impact is quantified by the error reduction rel- ative to the free run. The most effective sampling strate- gies determine 25--40% error reduction, depending on the season, the geographic area and the depth range. A quali- tative relationship can be recognized in terms of the spread of information from the data positions, between basin cir- culation features and spatial patterns of the error reduction fields, as a function of different spatial and seasonal char- acteristics of the dynamics. The largest error reductions are observed when samplings are characterized by extensive spa- tial coverages, as in the cases of AXBTs and the combination of XBTs and surface temperatures. The sampling strategy adopted during the TOP is characterized by little impact, as a consequence of a sampling frequency that is too low.
Raicich, F., & Rampazzo, A. (2010). Observing System Simulation Experiments for the assessment of temperature sampling strategies in the Mediterranean Sea. Annales Geophysicae, 21(1), 151–165. https://doi.org/10.5194/angeo-21-151-2003