PIRATA: A Sustained Observing System for Tropical Atlantic Climate Research and Forecasting

Bourlès, Bernard; Araújo, Moacyr; McPhaden, Michael J.; Brandt, Peter; Foltz, Gregory R.; Lumpkin, Rick; Giordani, Hervé; Hernández, Fabrice; Lefèvre, Nathalie; Nobre, Paulo; Campos, Edmo; Saravanan, R.; Trotte-Duhà, Janice; Dengler, Marcus; Hahn, Johannes; Hummels, Rebecca; Lübbecke, Joke F.; Rouault, Mathieu; Cotrim, Leticia; Sutton, Adrienne J.; Jochum, Markus; Perez, Renellys C.

doi:10.1029/2018ea000428

Cited by 79 publications

(66 citation statements)

References 220 publications

(362 reference statements)

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“…We use in situ nitrate, chlorophyll, and acoustic Doppler current profiler (ADCP) measurements collected during repeated transects along 10 • W ( Table 1) as part of the PIRATA (Prediction and Research Moored Array in the Tropical Atlantic; Servain et al, 1998;Bourlès et al, 2008Bourlès et al, , 2019 and EGEE (Étude de la Circulation Océanique et de sa Variabilité dans le Golfe de Guinée; Bourlès et al, 2007) programs. All these data, along with information on their acquisition and treatment, are available through their DOI (Bourlès, 1997;Bourlès et al, 2018a, c).…”

Section: Data Setsmentioning

confidence: 99%

Physical drivers of the nitrate seasonal variability in the Atlantic cold tongue

Radenac¹,

Jouanno²,

Tchamabi³

et al. 2020

Biogeosciences

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Abstract. Ocean color observations show semiannual variations in chlorophyll in the Atlantic cold tongue with a main bloom in boreal summer and a secondary bloom in December. In this study, ocean color and in situ measurements and a coupled physical–biogeochemical model are used to investigate the processes that drive this variability. Results show that the main phytoplankton bloom in July–August is driven by a strong vertical supply of nitrate in May–July, and the secondary bloom in December is driven by a shorter and moderate supply in November. The upper ocean nitrate balance is analyzed and shows that vertical advection controls the nitrate input in the equatorial euphotic layer and that vertical diffusion and meridional advection are key in extending and shaping the bloom off Equator. Below the mixed layer, observations and modeling show that the Equatorial Undercurrent brings low-nitrate water (relative to off-equatorial surrounding waters) but still rich enough to enhance the cold tongue productivity. Our results also give insights into the influence of intraseasonal processes in these exchanges. The submonthly meridional advection significantly contributes to the nitrate decrease below the mixed layer.

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Section: Data Setsmentioning

confidence: 99%

Physical drivers of the nitrate seasonal variability in the Atlantic cold tongue

Radenac¹,

Jouanno²,

Tchamabi³

et al. 2020

Biogeosciences

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“…The main data set consists of hourly measurements from two buoys of the Prediction and Research Moored Array in the Tropical Atlantic (PIRATA; Bourlès et al, 2019; https://www.pmel.noaa.gov/tao/ drupal/disdel/) located at 4 • N, 23 • W and 15 • N, 38 • W. These moorings are subsequently referred to as 4 • N and 15 • N, respectively. Measurements from 4 • N began in June 2006 and at 15 • N in February 1998.…”

Section: Pirata Mooring Datamentioning

confidence: 99%

Vertical Turbulent Cooling of the Mixed Layer in the Atlantic ITCZ and Trade Wind Regions

et al. 2020

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The causes of the seasonal cycle of vertical turbulent cooling at the base of the mixed layer are assessed using observations from moored buoys in the tropical Atlantic Intertropical Convergence Zone (ITCZ) (4°N, 23°W) and trade wind (15°N, 38°W) regions together with mixing parameterizations and a one‐dimensional model. At 4°N the parameterized turbulent cooling rates during 2017–2018 and 2019 agree with indirect estimates from the climatological mooring heat budget residual: both show mean cooling of 25–30 W m −2 during November–July, when winds are weakest and the mixed layer is thinnest, and 0–10 W m −2 during August–October. Mixing during November–July is driven by variability on multiple time scales, including subdiurnal, near‐inertial, and intraseasonal. Shear associated with tropical instability waves (TIWs) is found to generate mixing and monthly mean cooling of 15–30 W m −2 during May–July in 2017 and 2019. At 15°N the seasonal cycle of turbulent cooling is out of phase compared to 4°N, with largest cooling of up to 60 W m −2 during boreal fall. However, the relationships between wind speed, mixed layer depth, and turbulent mixing are similar: weaker mean winds and a thinner mixed layer in the fall are associated with stronger mixing and turbulent cooling of SST. These results emphasize the importance of seasonal modulations of mixed layer depth at both locations and shear from TIWs at 4°N.

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“…In March 2017, a T‐Flex mooring developed by NOAA/PMEL was deployed at the 4°N, 23°W PIRATA site (Bourlès et al, ). As is typical for these moorings, it has a suite of meteorological sensors and a combination of temperature, conductivity, and pressure sensors in the upper 500 m, as well as a single point acoustic current meter at 12‐m depth (Bourlès et al, ). The PIRATA mooring at this site prior to March 2017 measured currents at 10‐m depth (Bourlès et al, ; Perez et al, ).…”

Section: Data and Modelsmentioning

confidence: 99%

Direct Measurements of Upper Ocean Horizontal Velocity and Vertical Shear in the Tropical North Atlantic at 4°Ν, 23°W

et al. 2019

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The Tropical Atlantic Current Observations Study measured upper ocean horizontal velocity from a mooring at 4°N, 23°W, at discrete depths between 7 and 87 m, in order to observe the temporal and vertical structure of the currents. Between March 2017 and March 2018, mean zonal velocity and vertical shear were strongest between 32 and 37 m. Near‐surface mean eastward currents during this period were weaker than the long‐term mean but within the range of previously observed values given the high interannual variability. Interannual variability of the zonal velocity exceeded that of the meridional velocity, was primarily geostrophically driven, and was strongly influenced by the large‐scale currents. Energetic tropical instability waves (TIWs) were observed in early summer and late fall of 2017. Meridional velocity fluctuations associated with the TIWs were far larger than those of zonal velocity and extended down to 87 m. These fluctuations propagated upward to the surface with vertical phase speeds between 12 and 15 m/day. Coherent velocity and vertical shear variations emerged in a TIW composite. However, the vertical shears observed during the TIW season were modest compared to the large shear measured in spring 2017 and winter 2018. As a result, TIWs may be less crucial for vertical turbulent cooling at 4°N, 23°W than they are near the equator. To observe the intense winter/spring vertical shear events, fine vertical (less than 10 m) and diurnal temporal sampling is needed.

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PIRATA: A Sustained Observing System for Tropical Atlantic Climate Research and Forecasting

Cited by 79 publications

References 220 publications

Physical drivers of the nitrate seasonal variability in the Atlantic cold tongue

Physical drivers of the nitrate seasonal variability in the Atlantic cold tongue

Vertical Turbulent Cooling of the Mixed Layer in the Atlantic ITCZ and Trade Wind Regions

Direct Measurements of Upper Ocean Horizontal Velocity and Vertical Shear in the Tropical North Atlantic at 4°Ν, 23°W

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