Tag: PIRATA_Paper

Multidecadal Intensification of Atlantic Tropical InstabilityWaves

Tuchen, F. P., Perez, R. C., Foltz, G. R., Brandt, P., & Lumpkin, R. (2022). Multidecadal intensification of Atlantic tropical instability waves. Geophysical Research Letters, 49(22), e2022GL101073.

Abstract: In the equatorial Atlantic, temperature, salinity, sea level anomaly, and ocean velocity variations on time scales of tens of days are dominated by the presence and westward passage of large-scale Tropical Instability Waves (TIWs). Several decades of satellite and surface drifter data as well as moored velocity observations show a long-term intensification of TIW activity in all of these variables in the tropical North Atlantic where TIWs are most pronounced. We find that increased high-frequency flow variability, and not long-term changes of the mean zonal current system, drives the TIW intensification. One consequence of increased Atlantic Ocean TIW activity is the corresponding intensification of the horizontal eddy temperature advection pattern in boreal summer leading to stronger cooling of surface waters north of the equator…

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Surface Expressions of Atmospheric Thermal Tides in the Tropical Atlantic and Their Impact on Open‐ Ocean Precipitation

Christophersen, J. A., Foltz, G. R., & Perez, R. C. (2020). Surface Expressions of Atmospheric Thermal Tides in the Tropical Atlantic and Their Impact on Open‐Ocean Precipitation. Journal of Geophysical Research: Atmospheres, 125(22), e2019JD031997.

Abstract: Diurnal and semidiurnal variations of atmospheric pressure and surface winds are fundamental to the Earth‐Sun system. Past research in the tropical Pacific shows semidiurnal and diurnal patterns in the zonal and meridional wind anomalies, respectively. While the semidiurnal zonal wind pattern is consistent with atmospheric thermal tidal forcing, it is not yet certain what drives diurnal meridional wind variability. This study examines the diurnal cycle of meridional winds in the tropical Atlantic Ocean across four different seasons and the extent to which they impact the diurnal evolution of open‐ocean precipitation in boreal summer. Comparisons of direct observations from long‐term moored buoys to an atmospheric reanalysis (MERRA‐2) show that MERRA‐2 reproduces diurnal and semidiurnal pressure and wind variations…

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

Foltz, G. R., Hummels, R., Dengler, M., Perez, R. C., & de Araujo, M. (2020). Vertical turbulent cooling of the mixed layer in the Atlantic ITCZ and trade wind regions. Journal of Geophysical Research: Oceans, 125, e2019JC015529. https://doi.org/10.1029/2019JC015529

Abstract:
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) (4N, 23W) and trade wind (15N, 38W) regions together with mixing parameterizations and a one-dimensional model. At 4N 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 25–30W/m^2 during November–July, when winds are weakest and the mixed layer is thinnest, and 0–10W/m^2 during August–October. Mixing during November–July is driven by variability on multiple time scales, including subdiurnal, near-inertial, and intraseasonal…

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

Bourlès, B., Araujo, M.,McPhaden, M. J., Brandt, P., Foltz, G. R., Lumpkin, R., et al. (2019). PIRATA: A sustained observing system for tropical Atlantic climate research and forecasting. Earth and Space Science, 6, 577–616. https:// doi.org/10.1029/2018EA000428

Abstract: 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…

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