Breaking of balanced and unbalanced equatorial waves

Area of Science:

• Fluid dynamics
• Atmospheric science
• Geophysics

Background:

• Wave breaking is a key phenomenon in fluid dynamics, irreversibly altering mean flow.
• Understanding equatorial wave dynamics is crucial for atmospheric and oceanic processes.

Purpose of the Study:

• To investigate different equatorial wave breaking mechanisms.
• To determine how the balance between Coriolis force and pressure gradient influences breaking scenarios.
• To analyze the formation and properties of equatorial modons.

Main Methods:

• Developed a specialized numerical method for simulating nonlinear equatorial waves.
• Ensured numerical scheme convergence to weak solutions, including shocks.
• Preserved the steadiness of balanced stationary solutions for accurate diagnostics.

Main Results:

• Unbalanced waves exhibit shock formation due to lack of balance, leading to nonadvective potential vorticity flux and enhanced mixing.
• Balanced Rossby waves develop recirculation regions, forming equatorial modons that trap fluid particles.
• Modon formation is linked to positive geopotential anomalies and decreasing fluid depth, with robust interactions with Kelvin waves.

Conclusions:

• The balance between Coriolis force and pressure gradient dictates equatorial wave breaking mechanisms.
• Dissipative breaking in unbalanced waves enhances mixing, while balanced waves form stable, particle-trapping modons.
• Equatorial modons are significant structures in nonlinear wave dynamics, interacting with other wave types.