Forecasting the mixed-layer depth in the Northeast Atlantic: an ensemble approach, with uncertainties based on data from operational ocean forecasting systems

Abstract

Abstract. Operational systems operated by Mercator Ocean provide daily ocean forecasts, and combining these forecasts we can produce ensemble forecast and uncertainty estimates. This study focuses on the mixed-layer depth in the Northeast Atlantic near the Porcupine Abyssal Plain for May 2013. This period is of interest for several reasons: (1) four Mercator Ocean operational systems provide daily forecasts at a horizontal resolution of 1/4, 1/12 and 1/36 • with different physics; (2) glider deployment under the OSMOSIS project provides observation of the changes in mixed-layer depth; (3) the ocean stratifies in May, but mixing events induced by gale force wind are observed and forecast by the systems. Statistical scores and forecast error quantification for each system and for the combined products are presented. Skill scores indicate that forecasts are consistently better than persistence, and temporal correlations between forecast and observations are greater than 0.8 even for the 4-day forecast. The impact of atmospheric forecast error, and for the wind field in particular (miss or time delay of a wind burst forecast), is also quantified in terms of occurrence and intensity of mixing or stratification events.

Recent updates to the Copernicus Marine Service global ocean monitoring and forecasting real-time 1∕12° high-resolution system

“…As described in Lellouche et al (2013), the evaluation of such systems includes routine verification against assimilated and independent in situ and satellite observations, as well as a careful check of many physical processes (e.g., mixed layer depth evaluation as shown in Drillet et al, 2014). Scientific studies brought precious additional evaluation feedbacks (Juza et al, 2015;Smith et al, 2016;Estournel et al, 2016). Finally, several studies showed the added value of surface current analyses provided by these systems for drift applications (Scott et al, 2012;Drevillon et al, 2013).…”

An inverse method to derive surface fluxes from the closure of oceanic heat and water budgets: Application to the north‐western Mediterranean Sea

“…During the same period, operational and research oceanic models were run and some of their outputs were used. For estimating large‐scale geostrophic advections of temperature and salinity as well as horizontal Ekman advection of salinity, we used outputs of the operational MERCATOR PSY2V4R4 model [ Drillet et al ., ] (see sections 3.2.2 and 3.2.3). Moreover, for evaluating the heat budget closure presented in section 5.3, the MEDRYS reanalysis [ Hamon et al ., ] and some outputs of the mesoscale research SYMPHONY [ Marsaleix et al ., ] and MARS3D [ Garreau et al ., ] models were also used.…”