Assimilation scheme of the Mediterranean Forecasting System: operational implementation

Abstract

Abstract. This paper describes the operational implementation of the data assimilation scheme for the Mediterranean Forecasting System Pilot Project (MFSPP). The assimilation scheme, System for Ocean Forecast and Analysis (SOFA), is a reduced order Optimal Interpolation (OI) scheme. The order reduction is achieved by projection of the state vector into vertical Empirical Orthogonal Functions (EOF). The data assimilated are Sea Level Anomaly (SLA) and temperature profiles from Expandable Bathy Termographs (XBT). The data collection, quality control, assimilation and forecast procedures are all done in Near Real Time (NRT). The OI is used intermittently with an assimilation cycle of one week so that an analysis is produced once a week. The forecast is then done for ten days following the analysis day.The root mean square (RMS) between the model forecast and the analysis (the forecast RMS) is below 0.7 • C in the surface layers and below 0.2 • C in the layers deeper than 200 m for all the ten forecast days. The RMS between forecast and initial condition (persistence RMS) is higher than forecast RMS after the first day. This means that the model improves forecast with respect to persistence. The calculation of the misfit between the forecast and the satellite data suggests that the model solution represents well the main space and time variability of the SLA except for a relatively short period of three -four weeks during the summer when the data show a fast transition between the cyclonic winter and anticyclonic summer regimes. This occurs in the surface layers that are not corrected by our assimilation scheme hypothesis. On the basis of the forecast skill scores analysis, conclusions are drawn about future improvements.

Mediterranean Forecasting System: forecast and analysis assessment through skill scores

“…The model is forced at the air-sea interface with atmospheric fields from the European Centre for Medium-Range Weather Forecast (ECMWF) analyses and forecasts. The assimilation scheme used is a reduced order Optimal Interpolation system implemented in the Mediterranean Sea at different levels of complexity for the past ten years (Dobricic et al, 2004(Dobricic et al, , 2007Demirov et al, 2003). The assimilated data are: temperature and salinity vertical profiles from eXpandable BathyThermograph (XBT) and Argo, and Sea Level Anomalies (SLA) from altimetry.…”

“…In this paper we decided to use a Skill Score (SS) index following Murphy (1988) and Demirov et al (2003), composed with the rmse, the bias and the anomaly correlations. The study concentrates on the temperature and salinity fields at selected depths (5,30,150,300 and 600 m).…”

Observing System Simulation Experiments for the assessment of temperature sampling strategies in the Mediterranean Sea

“…Gibraltar Strait is open on a 3 • × 3 • Atlantic box. More model details are described in Korres et al (2000) and Demirov et al (2003). The model is forced by ECMWF 6-hourly operational analyses of 10 m-wind and 2 m-air temperature, also used in the surface heat flux calculation.…”

“…Among the components of the observing system (Pinardi and Flemming, 1998), the Mediterranean Forecasting System Pilot Project (MFSPP) includes a programme of eXpendable BathyThermograph (XBT) profiles collection; XBTs are routinely deployed along the Volunteer Observing Ship (VOS) tracks which form the network described in MFS-VOS Group (2003) and the data is subsequently assimilated into a Mediterranean General Circulation Model (GCM) for the purpose of forecasting (Demirov et al, 2003). In the absence of previous experiences in the Mediterranean, the VOS track network design is based on the scientific knowledge of the basin circulation, although it is constrained by logistic limitations.…”

Ocean and Coastal Modeling: Nonlinear Acoustic Propagation

“…This characteristics motivated attempts to represent forecast errors in terms of a shift of a forecast in space and time similar to the pseudo-random fields method described by Evensen (2003) and applied in ocean ensemble generation problems (e.g. Demirov, et al, 2003). For the present work, the atmospheric forcing perturbations used to force the ocean ensemble members were produced using the method developed by Xiandong et al (2007).…”