The Evolution of a Buoyant River Plume in Response to a Pulse of High Discharge from a Small Midlatitude River
The Evolution of a Buoyant River Plume in Response to a Pulse of High Discharge from a Small Midlatitude River
复制标题
DOI：
10.1175/jpo-d-19-0127.1
复制
发表时间：
2020-07
影响因子：
3.5
通讯作者：
E. Lemagie;J. Lerczak
中科院分区：
文献类型：
--
作者：
E. Lemagie;J. Lerczak
小型山区河流的一个独特特征是，在大雨期间，流量可以提高一个数量级。随时间变化的排放对淡水运输路径和沿岸传播率在沿海海洋的影响还没有得到很好的理解。在一个理想化的沿海海洋域中使用区域海洋模拟系统（ROMS）的一套模拟，具有变化的稳定背景排放条件（25-100 m3 s−1），脉冲幅度（200-800 m3 s−1），脉冲持续时间（1-6天），以及稳定的顺风（0-4 m s-1）进行比较，以研究下游淡水运输沿着海岸（在开尔文波传播的方向）以下的放电脉冲从河流。脉冲的前端以0.04-0.32 m s−1的速度沿海岸快速传播（更快的传播对应于更大的脉冲体积和更快的风），传输了13%-66%的放电。其余的排放量最初积累在河口附近的凸起，较长的脉冲持续时间和强风的保留较低。在脉冲之后，隆起涡流与河口分离，并以0-0.1 m s−1的速度向下游平流，等于深度平均的风驱动环境水速度。当它沿海岸过境时，它将淡水量进一步向下游输送，沿岸淡水输送在鼻子和瞬态隆起涡之间保持升高。在羽流横截面的淡水输送的演变可以描述的背景排放，脉冲鼻子的通道，和缓慢的指数返回到背景条件。
A unique feature of small mountainous rivers is that discharge can be elevated by an order of magnitude during a large rain event. The impact of time-varying discharge on freshwater transport pathways and alongshore propagation rates in the coastal ocean is not well understood. A suite of simulations in an idealized coastal ocean domain using the Regional Ocean Modeling System (ROMS) with varying steady background discharge conditions (25–100 m3 s−1), pulse amplitude (200–800 m3 s−1), pulse duration (1–6 days), and steady downwelling-favorable winds (0–4 m s−1) are compared to investigate the downstream freshwater transport along the coast (in the direction of Kelvin wave propagation) following a discharge pulse from the river. The nose of the pulse propagates rapidly alongshore at 0.04–0.32 m s−1 (faster propagation corresponds with larger pulse volume and faster winds) transporting 13%–66% of the discharge. The remainder of the discharge volume initially accumulates in the bulge near the river mouth, with lower retention for longer pulse duration and stronger winds. Following the pulse, the bulge eddy disconnects from the river mouth and is advected downstream at 0–0.1 m s−1, equal to the depth-averaged wind-driven ambient water velocity. As it transits alongshore, it sheds freshwater volume farther downstream and the alongshore freshwater transport stays elevated between the nose and the transient bulge eddy. The evolution of freshwater transport at a plume cross section can be described by the background discharge, the passage of the pulse nose, and a slow exponential return to background conditions.