PIRATA: a sustained observing system for Tropical Atlantic research and weather to climate predictions

PIRATA (Prediction and Research Moored Array in the Tropical Atlantic) is a multinational program initiated in 1997 to improve our knowledge and understanding of ocean-atmosphere variability in the tropical Atlantic, a region that strongly influences in a wide range of timescales the hydro-climates and, consequently, the economies and everyday life of the regions bordering the Atlantic Ocean. PIRATA is motivated both by fundamental scientific questions and societal needs for improved prediction of weather and climate variability and their changes and impacts. To address these challenges, PIRATA network has evolved naturally over time to reach now an array of 18 moored buoys providing meteorological and oceanographic data transmitted in real-time, disseminated via Global Telecommunication System (GTS) and Global Data Servers. Additionally, 3 subsurface ADCP moorings deployed along the equator complete this network for observing the coupled ocean-atmosphere dynamics.

With more than 25 years old, PIRATA provides invaluable data time series for scientific research, monitoring and operational forecasts and analyses. Sustained measurements over more than 2-decades in the tropical Atlantic are extremely important for observing ocean - atmosphere variability on interannual to multidecadal timescales and changes in response to global warming.

PIRATA is now recognized as the base and backbone of the Tropical Atlantic observing system dedicated to both research and forecast.

Through yearly mooring servicing, data and sensors are calibrated and recorded high-frequency data are collected. The dedicated cruises of yearly maintenance of the PIRATA network allow complementary measurements of a large set of physical, biogeochemical and biological data along repeated ship track lines that offer reference high quality monitoring for climate changes and impacts. These cruises also provide support for deployment of other components of the Tropical Atlantic Observing System (Argo, DBCP …), and allow opportunistic regular surveys of Sargassum extension or plastic concentration.

Recently, following the recommendations for the future Tropical Atlantic Observing System, the sampling carried out during PIRATA cruises have been extended to include new biogeochemical parameters to a better understanding of the processes that drive ocean biogeochemical cycles, to monitor the variability of the oxygen minimum zone, the ocean carbon uptake mechanisms, or to examine the impacts of climate change on ocean acidification in this region. In the meantime, additional sensors of physical parameters (temperature, salinity and currents) have been deployed to study the variability of the diurnal cycle of ocean stratification and vertical shear at high vertical resolution in relation to equatorial dynamics.