Program
 
General Session 1: Physical oceanic processes: Dynamics and physical-biological-biogeochemical interactions
 
 
 
Poster
Circulation physics in vorticity equations
GS1-12
Rex Chiwing Hui* , Department of Mathematics, Hong Kong University of Science and Technology
Jianping Gan, Department of Mathematics, Hong Kong University of Science and Technology
Presenter Email: macwhui@ust.hk
Circulation and associated dynamics in the ocean can be favorably depicted by vorticity dynamics in various vorticity equations. Yet, the form and physical interpretation to these equations remain ambiguous. In this study, we analyze the widely-used depth-integrated (DIV; 1/D(∇_H¡Á¡Ò_Lb^Lu▒¡¼v ⃗ dz¡½), where Lu, Lb and D are the depths of the top, bottom and total depth, respectively), the depth-averaged (DAV; ∇_H¡Á1/D ¡Ò_Lb^Lu▒¡¼v ⃗ dz¡½ ) and depth-dependent vorticity (DDV; 1/D(¡Ò_Lb^Lu▒¡¼∇_H¡Áv ⃗ dz)¡½) equations to understand respective physics represented by them. Despite unanimous representation for dynamics of the rotational motion with different mathematic expressions, the physical meanings embedded in these vorticity equations vary and represent different aspects of the circulation dynamics. Besides retention of full physics as in DIV equation, DDV and DAV equations contain extra terms related to momentum-topography interaction. Although DDV is physically straightforward, the important flow-topography dynamics can be better reflected by DIV and DAV equations through respective topographic pressure toque (TPT) and Joint Effect Baroclinicity and Relief (JEBAR). We illustrate the effects of pressure gradient force as JEBAR in DAV equation and as TPT in DIV equation and contrast them with DDV equation. We conduct two numerical studies to elucidate and consolidate understanding of intrinsic forcing in the vorticity equations over an idealized slope current and extrinsic-intrinsic forcing in the semi-closed South China Sea basin. We found that only DIV, through the domain-integration, can explicitly isolate the extrinsic contribution from intrinsic one, while provide the linkage between them.