The Interannual Variability of the Brazil Current

巴西海流系统之所以重要，是因为：(1)在地面，它携带着温暖的热带水，具有很强的涡旋可变性，在很大程度上迫使区域天气形势；(2)它具有独特的垂直结构，接受不同高度和纬度的几个水团的贡献；(3)它是一种关闭南大西洋副热带环流的西边界流；(4)它的相对较弱的时间平均流表明与大西洋经向翻转环流有很强的相互作用。对巴西目前年际变化的研究很少，部分原因是缺乏现场观测数据。这项研究的目的是通过分析大量巴西海流的直接测量数据和数值模型实验来提高对巴西海流系统的理解。该项目包括对早期职业首席研究员的支持，对博士后研究员的指导，与巴西大学的国际合作，以及对大学生的培训。本研究调查了巴西海流在年际时间尺度上的可变性，以及它与驱动它的大规模机制的关系。它包括分析水文、卫星和海洋再分析数据，以及执行涡旋分辨模拟实验。水文数据分析将包括大量高密度断面，将审查巴西流在不同纬度的结构，巴西流与涡旋位置和强度的关系，以及大范围风强迫的影响。补充卫星测高和模式再分析数据将提供巴西海流平均和涡流的准天气图，以及Rossby波机制对海流变异性的影响。将使用全球允许涡流的海洋模式模拟进行基于过程的研究，以分离本地和远程风强迫的影响。这些运行将与西南大西洋区域的嵌套涡旋解析区域模式进行比较，以调查中尺度涡旋过程如何对较长时间尺度的区域变率作出反应和反馈。

The Brazil Current system is important because: (i) at the surface, it carries warm Tropical Water and has strong eddy variability, forcing in large extent regional weather patterns; (ii) it has a unique vertical structure receiving contributions from several water masses at different levels and latitudes; (iii) it is a western boundary current that closes the South Atlantic subtropical gyre; and (iv) its relative weak time-mean flow indicates strong interactions with the Atlantic meridional overturning circulation. Few investigations exist of the Brazil Current interannual variability, in part because of a lack of in-situ observational data. This study aims at improving the understanding of the Brazil Current system using analysis of a large collection of direct measurements of the Brazil Current and numerical model experiments. The project includes support for an early career principal investigator, mentoring of a postdoctoral researcher, international collaborations with Brazilian universities, and training of college students.This study investigates the variability of the Brazil Current on interannual timescales, and its relationship to the large-scale mechanisms that drive it. It involves analyzing hydrographic, satellite, and ocean reanalysis data, and performing eddy-resolving modeling experiments. The hydrographic data analysis, which will include a large number of high-density transects, will examine the structure of the Brazil Current at different latitudes, the relationship of the Brazil Current with the location and strength of the gyre, and the effect of the large-scale wind forcing. Complementary satellite altimetry and model reanalysis data will provide a quasi-synoptic view of the mean and eddy flow of the Brazil Current, as well as the impact of Rossby wave mechanisms on the current variability. A process-based study using global eddy-permitting ocean model simulations will be performed for separating the influence of local and remote wind forcing. These runs will be compared against a nested eddy-resolving regional model of the western South Atlantic domain to investigate how the mesoscale eddy processes may respond to and feedback on the regional variability at longer timescales.