Refraction and Reflection of Nonlinear Internal Waves from Steep Topography
Abstract
Summary of Proposed Work:The broad objective for the proposed work is to improve forecasting and predictability for nonlinear internal waves in the ocean. More specifically, our work will focus on NLIW transformation processes over steep, 3-dimensional topography- including refraction and reflection - and the implications of these processes toward the near field and far field environments.The project objectives will be guided by the following hypotheses and questions:Q1. How are NLIW transformation dynamics over 3-dimensional topography modified by: (a)The effects of previous wave cycles? We propose that wave sequences will be strongly influenced by trapped wave energy, residual flows and modifications in stratification from leading waves, resulting in changes in wave form, breaktype, and asymmetries in dissipation and transmission. These processes will further be altered by changes in amplitude and relativephasing between successive waves. (b)The amplitude and phasing of locally-generated internal tides? We hypothesize that relative phasing of internal tide-generated changes in stratification and currents will also lead to local asymmetries in NLIW interactions with steep topography. These effects will be manifested in spring-neap variability in NLIW transformation dynamics.(c)Rotational effects? For a given geometry, asymmetry in NLIW refraction will be magnified by increased rotation, with dynamics determined by the Burger number (c/f LH)2, where c is the NLIW phase speed, LH is the horizontal scale of the topography and f is the Coriolis parameter. Trapped baroclinic energy will vary following a similarly defined Burger number that describes the ratio of internal Rossby radius of deformation to topographic scale. Q2. How do NLIW interactions with steep topography drive residual circulation and trapped baroclinic energy? We hypothesize that wave shoaling, breaking and refraction, modified by asymmetries associated with wave incidence and planetary rotation, generate trapped baroclinic waves and residual flows along with significant changes in stratification. Further, we expect these transformation processes will be modulated by offshore waveform and topographic slope, with implications for trappedenergy and residual circulations.Q3. How do NLIW - topographic interactions modify the far-field internal wave environment? We hypothesize that near-field NLIW dynamics influence the far-field through dissipation and redirection of NLIW energy, as well as conversion to higher frequency internal waves. In particular, NLIW refractive patterns will be significantly modulated by variations in phase speed associated with near-field processes. We expect to see reduced wave energy in the lee of the atoll, with complex patterns due to the effects of diffraction, refraction and rotation, as well as locations of enhanced wave energy in the fore of the atoll due to reflection and standing-wave features.To examine dynamics of NLIW interactions with steep topography and address the specific objectives outlined above, we propose to carry out idealized and semi-idealized numerical modeling experiments along with analysis ofexisting observational data (described in Synthesis section below). The proposed analyses will further provide guidance for future field observational campaigns in collaboration with Taiwanese colleagues. Year 1 postdoctoral salary will support Dr. Shuwen Tan, who has worked with Davis at UC Irvine on the project previously and is relocating to Stanford University. Dr. Tan aims to complete two manuscripts from the numerical studies currently underway. Year 2 will focus on completion of the simulations in Table 1 along with analysis of simulation data and the publication and dissemination of results. The major project milestones will include presentation of preliminary results of modeling and field data analysis, nominally at the 2024 AGU Fall Meeting at the end of Year 1 with full conclusions to be pres
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Nov 09, 2024
- Source ID
- N000142412591
Entities
People
- Kristen A. Davis
Organizations
- Office of Naval Research
- Stanford University
- United States Navy