Observations of near-inertial current variability on the New England shelf
Observations of near-inertial current variability on the New England shelf
复制标题
DOI：
10.1029/2004jc002341
复制
发表时间：
2005-02
影响因子：
--
通讯作者：
R. Shearman
中科院分区：
文献类型：
--
作者：
R. Shearman
[1]从海岸混合和光学（CMO）系泊阵列（部署于1996年8月至1997年6月）和补充系泊观测的观测被用来描述近惯性电流的变化在新英格兰大陆架。近惯性带电流方差占总观测电流方差的10-20%，并且具有超过30 cm s-1的偶发峰值速度。近惯性流变率在CMO的特点是由第一斜压模式垂直结构与一个零交叉之间的15和50米。在较强的分层期间，零交叉较浅。横向上，近惯性的变化是连贯的CMO系泊阵列的范围内，跨货架去相关尺度近惯性电流约100公里，约整个货架宽度。近地面近惯性变率的大小在夏季较强，冬季较弱，在层结上遵循季节变化，在风应力方差上与季节循环相反。在CMO期间，近地面近惯性动能与地面混合层深度成反比。近惯性方差在岸上减小，与二维线性平底两层海岸壁模型预测的近惯性能量的跨大陆架减小近似匹配。在这个模式中，斜压波从海岸墙发出的抵消作用在控制陆上减少中起着主导作用。最后，强持久的反气旋相对涡度转移近惯性变化的新英格兰大陆架上的亚惯性频率。
[1] Observations from the Coastal Mixing and Optics (CMO) moored array (deployed from August 1996 through June 1997) and supplemental moored observations are used to describe near-inertial current variability over the New England shelf. Near-inertial band current variance comprises 10–20% of the total observed current variance, and has episodic peak speeds exceeding 30 cm s−1. Near-inertial current variability during CMO is characterized by a first baroclinic mode vertical structure with one zero-crossing between 15 and 50 m. The zero-crossing is shallower during periods of stronger stratification. Laterally, near-inertial variability is coherent over the extent of the CMO moored array, and cross-shelf decorrelation scales for near-inertial currents are about 100 km, approximately the entire shelf width. The magnitude of near-surface near-inertial variability is stronger in the summer and weaker in the winter, following the seasonal variation in stratification and opposite the seasonal cycle in wind stress variance. During CMO, near-surface near-inertial kinetic energy is inversely related to surface mixed layer depth. Near-inertial variance decreases onshore, matching approximately the cross-shelf decrease in near-inertial energy predicted by a two-dimensional, linear, flat-bottom, two-layer, coastal wall model. In this model, the nullifying effects of a baroclinic wave emanating from the coastal wall play a dominant role in controlling the onshore decrease. Finally, strong persistent anticyclonic relative vorticity shifts near-inertial variability on the New England shelf to subinertial frequencies.