Time-Dependent Visualization of Ocean Surface Velocity and Vorticity

TL;DR

An interactive, time-dependent visualization system that lets users explore ocean surface velocity and vorticity in the Gulf of Mexico over five months using animated scalar fields, vector glyphs, and a video-streamer-style UI.

Purpose

Ocean surface velocity and vorticity play a critical role in:

• global climate systems
• ocean circulation
• marine transportation and safety
• environmental monitoring

This project aims to make these complex, time-varying datasets intuitive and explorable through interactive visualization, allowing users to observe large-scale circulation patterns and temporal changes in the Gulf of Mexico.

Dataset

We used two datasets from the Gulf of Mexico Research Initiative:

1) Velocity dataset

• 2D spatial grid (longitude × latitude)
• Time-dependent (306 timestamps)
• 12-hour sampling interval
• Grid resolution: 450 × 360
• Represents ocean surface velocity

2) Vorticity dataset

• Same spatial resolution and time span
• Encodes clockwise / counter-clockwise circulation
• Stored as a separate dataset aligned in time

Together, these datasets cover April 1 – August 31, 2013.

Methodology

1) Time-dependent visualization design

Because the data is time-varying, we designed the interface to behave like a video streamer:

• Play / pause animation
• Next / previous frame
• Jump to first / last frame
• Slider bar to scrub to any timestamp

This allows users to observe both:

• short-term motion
• long-term circulation trends

2) Visualization modes

We implemented three complementary visualization modes, each revealing different physical properties:

A) Velocity magnitude (scalar field)

• Velocity magnitude mapped to color
• Uses a Turbo colormap
• Highlights regions of strong vs weak flow

B) Velocity vectors (glyphs)

• Arrows encode direction and magnitude
• Helps users understand local flow direction
• Useful for tracing circulation paths

C) Vorticity visualization

• Visualizes rotational behavior of the flow
• Warm colors → positive (counter-clockwise)
• Cool colors → negative (clockwise)
• Makes swirling structures immediately visible

3) Color mapping strategy

Special care was taken when choosing color ranges:

• Turbo colormap with 8 discrete control points
• Color ranges selected to maximize contrast
• Signed vorticity values clearly separated into warm/cool hues

This ensures circulation patterns remain readable even at small spatial scales.

Results

What the system enables

• Smooth animation of ocean circulation over five months
• Clear identification of large-scale structures such as:
  • Loop Current
  • Loop Eddy
• Side-by-side understanding of:
  • velocity magnitude
  • velocity direction
  • vorticity behavior

The animated visualization makes circulation phenomena far easier to understand than static plots.

Discussion

The project met its original objectives and evolved during development:

• Initially planned to visualize only velocity magnitude and vectors
• Expanded to include vorticity after discovering a compatible dataset
• The combination of velocity and vorticity views provided a much deeper understanding of ocean dynamics

One limitation is that the dataset was downsampled, so the visualization emphasizes global patterns rather than fine-scale turbulence.

Limitations

• Reduced spatial resolution limits local detail
• Performance constraints prevent extremely dense glyph fields
• Visualization is descriptive rather than predictive

Future Work

Possible extensions include:

• Higher-resolution datasets over longer time spans
• GPU-accelerated rendering for denser vector fields
• Particle advection / streamlines for flow tracing
• Comparative visualization across different seasons or years