PIRATA is a multinational programme initialized in 1997 within the international CLIVAR program framework and realized in the framework of an international cooperation between USA, Brazil and France (committed countries through a Memorandum of Understanding). PIRATA is a program for the studies of air-sea interaction in the Tropical Atlantic to seasonal, interannual or longer timescale. It maintains a network of 18 met-ocean buoys from summer 2013. Observed parameters are notably used to monitor and analyze the exchanges at the air-sea interface along with the oceanic thermohaline structure down to 500m depth. Oceanic (current, temperature and salinity between the surface and 500m) and atmospheric at the ocean surface (wind direction, wind velocity, air temperature, relative humidity, rainfall, shortwave radiation) data are transmitted daily in real time through ARGOS or IRIDIUM, and available through internet. Three equatorial subsurface current-meter moorings (ADCP) at 23°W-0°N (from 2001), at 10°W-0°N (from 2006) and at 0°E-0°N (from 2016) are also associated to this network. PIRATA needs yearly cruises to replace all the buoys and, in this framework, France (through IRD) is in charge of 6 met-ocean buoys located in the Eastern Tropical Atlantic (east of at 23°W) and of three equatorial current-meter moorings at 23°W-0°N, 10°W-0°N and 0°E-0°N.

The PIRATA-FR31 (31th cruise of this program) will aim to ensure the yearly maintenance of the 6 buoys located at 23°W-0°N, 10°W-10°S, 10°W-6°S, 10°W-0°N, 0°E-0°N and 10°W-20°S (this latter was deployed for the first time in 2020 as part of a future extension of the PIRATA network and to replace the buoy located off CONGO at 6 °S-8 ° E deployed and maintained in the area since 2013 but vandalized in 2018 and 2019) along with one of the three current-meter moorings, the one located at 10°W-0°N. CO2 sensors are also serviced at 10°W-6°S (from 2006) and at 10°W-0°N (from 2020 replacing the sensor initially installed at 6°S-8°E since 2017). The PIRATA-FR31 cruise will allow to validate the transits by carrying out CTD-O₂/LADCP profiles along sections at 10°W (repeated yearly), 0°E and at 23°W, along with XBT profiles along the trackline. Additionnal CTD-O₂/LADCP profiles will be carry out in the Guinea Dôme area between 23°W-11°N and 17°W-6°N in perspective to project of Bio-ARGO profilers deployment in the area. Surface drifting buoys will be deployed (SVP-BS for Meteo-France as contribution to AtlantOS, NOAA/AOML for GCP and SOERE CTDO2) along with ARGO profilers for CORIOLIS, and numerous sea water samplings (surface and during CTD-O₂ casts) will be done for the analysis of dissolved oxygen, salinity, nutrients, carbon parameters (DIC, TA) and primary production (Chl pigments). During this cruise, additional acoustic measurements (along the vertical and the horizontal) will also be carried out continuously as well as measurements of CO₂ parameters.  Some CTDO₂ / LADCP profiles up to 4000m deep will also be carried out near the Deep-Argo profilers already present in this area.