Wave-breaking modulation by infragravity waves during an extreme typhoon

Area of Science:

• Coastal processes
• Oceanography
• Wave dynamics

Background:

• Typhoons generate extreme wave conditions impacting coastal areas.
• Infragravity waves play a significant role in nearshore dynamics, especially during extreme events.
• Understanding nearshore wave evolution under extreme conditions is crucial for coastal management and hazard assessment.

Purpose of the Study:

• To analyze the effect of energetic infragravity waves on the nearshore evolution of short waves during extreme typhoon conditions.
• To investigate the mechanism by which infragravity waves influence short wave breaking and energy transfer in the nearshore zone.

Main Methods:

• Collection of coastal-wave records during a strong typhoon in Japan in 2017.
• Analysis of infragravity wave characteristics and their interaction with short waves.
• Individual wave analyses to examine the impact on short wave breaking and nearshore evolution.

Main Results:

• Extreme typhoon conditions generated large infragravity waves (up to 2m) in shallow water.
• Infragravity waves caused instantaneous water-level fluctuations, alternately decelerating and accelerating short wave breaking.
• This interaction facilitated the transmission of short-wave energy to the shore, increasing nearshore wave heights.

Conclusions:

• Infragravity waves significantly impact nearshore wave characteristics and evolution under extreme conditions.
• The study provides in situ evidence of the energy transfer mechanism from short waves on infragravity wave crests to the shore.
• Findings enhance the understanding of coastal morphodynamics during extreme weather events.