Preprints
https://doi.org/10.5194/egusphere-2023-1956
https://doi.org/10.5194/egusphere-2023-1956
07 Sep 2023
 | 07 Sep 2023

Influence of Stratification and Wind Forcing on the Dynamics of Lagrangian Residual Velocity in a Periodically Stratified Estuary

Fangjing Deng, Feiyu Jia, Rui Shi, Shuwen Zhang, Qiang Lian, Xiaolong Zong, and Zhaoyun Chen

Abstract. Wind and stratification play pivotal roles in shaping the structure of the Lagrangian residual velocity (LRV). However, the intricate dynamics by which wind and stratification modify the LRV remain poorly studied. This study derives numerical solutions of LRV components and eddy viscosity subcomponents to elucidate the dynamics within the periodically stratified Pearl River estuary. The vertical shear cross-estuary LRV (uL) is principally governed by the interplay among the eddy viscosity component (uLtu), the barotropic component (uLba), and the baroclinic component (uLgr) under stratified conditions. During neap tides, southwesterly winds notably impact uL by escalating uLtu by an order of magnitude within the upper layer. This transforms the eastward flow dominated by uLtu under wind influence into a westward flow dominated by uLba in upper shoal regions without wind forcing. The along-estuary LRV exhibits a gravitational circulation characterized by upper-layer outflow engendered by barotropic component (vLba) and lower-layer inflow predominantly driven by baroclinic component (vLgr). The presence of southwesterly winds suppresses along-estuary gravitational circulation by diminishing the magnitude of vLba and vLgr. The contributions of vLba and vLgr are approximately equal, while the ratio between uLba and uLgr (uLtu) fluctuates within the range of 1 to 2 in stratified waters. Under unstratified conditions, LRV exhibits a lateral shear structure due to differing dominant components compared to stratified conditions. In stratified scenarios, the eddy viscosity component of LRV is predominantly governed by the turbulent mean component, while it succumbs to the influence of the tidal straining component in unstratified waters.

Fangjing Deng, Feiyu Jia, Rui Shi, Shuwen Zhang, Qiang Lian, Xiaolong Zong, and Zhaoyun Chen

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1956', Anonymous Referee #1, 10 Oct 2023
    • AC1: 'Reply on RC1', Fangjing Deng, 01 Nov 2023
    • AC2: 'Reply on RC1', Fangjing Deng, 01 Nov 2023
    • AC4: 'Reply on RC1', Fangjing Deng, 06 Dec 2023
  • RC2: 'Comment on egusphere-2023-1956', Anonymous Referee #2, 06 Nov 2023
    • AC3: 'Reply on RC2', Fangjing Deng, 06 Dec 2023

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1956', Anonymous Referee #1, 10 Oct 2023
    • AC1: 'Reply on RC1', Fangjing Deng, 01 Nov 2023
    • AC2: 'Reply on RC1', Fangjing Deng, 01 Nov 2023
    • AC4: 'Reply on RC1', Fangjing Deng, 06 Dec 2023
  • RC2: 'Comment on egusphere-2023-1956', Anonymous Referee #2, 06 Nov 2023
    • AC3: 'Reply on RC2', Fangjing Deng, 06 Dec 2023
Fangjing Deng, Feiyu Jia, Rui Shi, Shuwen Zhang, Qiang Lian, Xiaolong Zong, and Zhaoyun Chen
Fangjing Deng, Feiyu Jia, Rui Shi, Shuwen Zhang, Qiang Lian, Xiaolong Zong, and Zhaoyun Chen

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Short summary
Southwesterly winds impact cross-estuary flows by amplifying the eddy viscosity component during smaller tides. Moreover, they modify along-estuary gravitational circulation by diminishing both the barotropic and baroclinic components. Stratification results in contrasting sheared flows, distinguished by different dominant components compared to destratified conditions. Additionally, the eddy viscosity component is governed by various subcomponents in diverse stratified waters.