Prediction and Research Moored Array in the Tropical Atlantic (PIRATA) is a multinational program initiated in 1997 in the tropical Atlantic to improve our understanding and ability to predict ocean‐atmosphere variability. PIRATA consists of a network of moored buoys providing meteorological and oceanographic data transmitted in real time to address fundamental scientific questions as well as societal needs. The network is maintained through dedicated yearly cruises, which allow for extensive complementary shipboard measurements and provide platforms for deployment of other components of the Tropical Atlantic Observing System. This paper describes network enhancements, scientific accomplishments and successes obtained from the last 10 years of observations, and additional results enabled by cooperation with other national and international programs. Capacity building activities and the role of PIRATA in a future Tropical Atlantic Observing System that is presently being optimized are also described.

Geostrophic currents derived from altimetry are used to investigate the surface circulation in the western tropical Atlantic over the 1993–2017 period. Using six horizontal sections defined to capture the current branches of the study area, we investigate their respective variations at both seasonal and interannual timescales, as well as the spatial distribution of these variations, in order to highlight the characteristics of the currents on their route. Our results show that the central branch of the South Equatorial Current and its northern branch near the Brazilian coast, the North Brazil Current component located south of the Equator, and the Guyana Current have similar annual cycles, with maxima (minima) during late boreal winter (boreal fall) when the Intertropical Convergence Zone is at its southernmost (northernmost) location. In contrast, the seasonal cycles of the North Brazil Current branch located between the Equator and 7–8^∘ N, its retroflected branch, the northern branch of the South Equatorial Current to the west of 35^∘ W, and the North Equatorial Countercurrent show maxima (minima) during late boreal summer (boreal spring), following the remote wind stress curl strength variation. West of 32^∘ W, an eastward current (the Equatorial Surface Current, ESC) is observed between 2–2^∘ N, identified as the equatorial extension of the retroflected branch of the North Brazil Current. It is part of a large cyclonic circulation observed between 0–6^∘ N and 35–45^∘ W during boreal spring. We also observed a secondary North Brazil Current retroflection flow during the second half of the year, which leads to the two-core structure of the North Equatorial Countercurrent and might be related to the wind stress curl seasonal changes. To the east, the North Equatorial Countercurrent weakens and its two-core structure is underdeveloped due to the weakening of the wind stress. At interannual scales, depending on the side of the Equator examined, the North Brazil Current exhibits two opposite scenarios related to the phases of the tropical Atlantic Meridional Mode. At 32^∘ W, the interannual variability of the North Equatorial Countercurrent and of the northern branch of the South Equatorial Current (in terms of both strength and/or latitudinal shift) are associated with the Atlantic Meridional Mode, whereas the variability of the Equatorial Surface Current intensity is associated with both the Atlantic Meridional Mode and Atlantic Zonal Mode phases.

Operational forecasting systems architecture requires clear identification of best practices for assessing the quality of ocean products: it plays a key role not only for the qualification of predictions skill, but also for advancing in the scientific understanding of the ocean dynamics from global to coastal scales. The Authors discusses on the role of observing network for performing validation of ocean model outputs, identifying current gaps (i.e., different capacity in assessing physical essential ocean variables versus biogeochemical ones), but also emphasizing the need of new metrics (tailored for end-users comprehension and usages). An analysis on the level of maturity of validation processes from global to regional systems is provided. A rich variety of approaches exist, and the most we move towards the coast the higher is the complexity in calculating such metrics, due to increased resolution but also somehow limited by the lack of coastal observatories worldwide. It is provided as example how the Copernicus Marine Service currently organizes the product quality information from producers (with dedicated scientific documentation, properly planned and designed) to end-users (with publication of targeted estimated accuracy numbers for its whole product catalogue).