Seasonal variation of a coastal jet in the Long Island Sound outflow region based on HF radar and Doppler current observations
Seasonal variation of a coastal jet in the Long Island Sound outflow region based on HF radar and Doppler current observations
复制标题
DOI：
10.1029/2002jc001660
复制
发表时间：
2004-07
影响因子：
--
通讯作者：
D. Ullman;D. Codiga
中科院分区：
文献类型：
--
作者：
D. Ullman;D. Codiga
[1] 作为前沿遥测观测网络 (FRONT) 项目的一部分，在大约 2 年的时间内获得的表面流（高频雷达）和速度剖面观测结果用于描述长岛海峡外流区域沿海急流的季节变化。喷流是在大陆架的一个区域观测到的，该区域在夏季和冬季经常检测到表面热锋。目前的急流与夏季锋面高概率带重合，显然是由长岛海峡外流与大陆架上更大规模的沿岸流之间的相互作用产生的。急流在夏季达到峰值强度（输送量约为 0.07 Sv），而在冬季则较弱或不存在。水流在地表附近最强，随着深度的增加而减弱，垂直切变只有适度的季节性变化。对相对较长的海流数据集与历史水文测量和浮标风观测相结合进行分析，以检查深度平均动量平衡中各项的季节变化。深度平均压力梯度分为空间分量（根据水文学进行评估）和非空间分量（估计为动量方程中计算项的残差）。发现深度平均动量平衡在跨岸方向上近似地转。急流的季节性变化是由于浮力驱动流（总是在下架但在夏季有所加强）和风驱动流（在冬季风应力变得有利的强烈上升流时占主导地位）之间的平衡变化而产生的。
[1] Surface current (HF radar) and velocity profile observations, obtained as part of the Front-Resolving Observational Network with Telemetry (FRONT) project over an approximately 2-year period, are used to describe the seasonal variability of a coastal jet in the Long Island Sound outflow region. The jet is observed in an area of the continental shelf where surface thermal fronts are frequently detected during both summer and winter. The current jet is coincident with a band of high summer frontal probability, and apparently arises from the interaction between Long Island Sound outflow and larger-scale alongshore currents on the shelf. The jet reaches peak strength in summer (transport of ∼0.07 Sv) and is weak or non-existent in winter. Flow is strongest near the surface and weakens with depth, with only moderate seasonal variations in the vertical shear. The relatively long data set of currents combined with historical hydrographic measurements and buoy wind observations is analyzed to examine the seasonal variability of the terms in the depth-averaged momentum balance. The depth-averaged pressure gradient is partitioned into a steric component, evaluated from the hydrography, and a non-steric component that is estimated as the residual of the computed terms in the momentum equation. The depth-averaged momentum balance is found to be approximately geostrophic in the across-shore direction. The seasonal variability in the jet arises due to the shifting balance between buoyancy-driven flow that is always downshelf but intensifies somewhat in summer and wind-driven flow which dominates in winter when wind stress becomes strongly upwelling favorable.