Fernández-Nóvoa D, Gómez-Gesteira M, Mendes R, deCastro M, Vaz N, Dias J M
EPHYSLAB, Environmental PHYsics LABoratory, Facultad de Ciencias, Universidad de Vigo, Ourense, Spain.
CESAM, Physics Department, University of Aveiro, Aveiro, Portugal.
PLoS One. 2017 Oct 26;12(10):e0187036. doi: 10.1371/journal.pone.0187036. eCollection 2017.
The role of river discharge, wind and tide on the extension and variability of the Tagus River plume was analyzed from 2003 to 2015. This study was performed combining daily images obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor located onboard the Aqua and Terra satellites. Composites were generated by averaging pixels with the same forcing conditions. River discharge shows a strong relation with the extension of the Tagus plume. The plume grows with the increasing river discharge and express a two day lag caused by the long residence time of water within the estuary. The Tagus turbid plume was found to be smaller under northerly and easterly winds, than under southerly and westerly winds. It is suggested that upwelling favoring winds provoke the offshore movement of the plume material with a rapidly decrease in turbidity values whereas downwelling favoring winds retain plume material in the north coast close to the Tagus mouth. Eastern cross-shore (oceanward) winds spread the plume seaward and to the north following the coast geometry, whereas western cross-shore (landward) winds keep the plume material in both alongshore directions occupying a large part of the area enclosed by the bay. Low tides produce larger and more turbid plumes than high tides. In terms of fortnightly periodicity, the maximum plume extension corresponding to the highest turbidity is observed during and after spring tides. Minimum plume extension associated with the lowest turbidity occurs during and after neap tides.
2003年至2015年期间，分析了河流流量、风和潮汐对塔霍河河羽扩展及变化的作用。本研究结合了从搭载在Aqua和Terra卫星上的中分辨率成像光谱仪（MODIS）传感器获取的每日图像进行。通过对具有相同强迫条件的像素进行平均生成合成图像。河流流量与塔霍河河羽的扩展呈现出强烈的相关性。河羽随着河流流量的增加而增长，并表现出由于河口内水体停留时间长而导致的两天滞后。研究发现，在北风和东风条件下，塔霍河浑浊河羽比在南风和西风条件下更小。有人认为，有利于上升流的风促使河羽物质离岸移动，浊度值迅速降低，而有利于下沉流的风则使河羽物质保留在靠近塔霍河口的北海岸。东风向岸外（向海）风沿着海岸几何形状将河羽向海和向北扩散，而西风向岸内（向陆）风使河羽物质在两个沿岸方向上分布，占据了海湾所围区域的很大一部分。低潮时产生的河羽比高潮时更大且更浑浊。就半月周期而言，在大潮期间及之后观察到对应最高浊度的最大河羽扩展。与最低浊度相关的最小河羽扩展发生在小潮期间及之后。
