Simple stochastic model for El Niño with westerly wind bursts

Area of Science:

• Climate dynamics
• Atmospheric science
• Oceanography

Background:

• El Niño Southern Oscillation (ENSO) is a major driver of global climate variability.
• Tropical atmospheric wind bursts are recognized as key factors influencing ENSO.
• Existing models often struggle to capture the intermittent and variable nature of ENSO events.

Purpose of the Study:

• To propose a simple, physically consistent modeling framework for ENSO dynamics.
• To investigate the causal relationship between tropical wind bursts and ENSO variability.
• To capture major features of the ENSO observational record using a simplified model.

Main Methods:

• Developed a stochastic two-state Markov switching-diffusion process for wind burst activity.
• Coupled wind burst dynamics to deterministic, stable, and linear ocean-atmosphere processes.
• Utilized a simplified model without additional nonlinearities to simulate ENSO cycles.

Main Results:

• The model successfully reproduces realistic ENSO cycles with intermittent El Niño and La Niña events of varying intensity.
• Observed realistic buildup and shutdown patterns of wind burst activity in the western Pacific.
• Demonstrated that wind burst activity directly and intermittently triggers ENSO events, including super El Niño events.

Conclusions:

• The proposed modeling framework provides theoretical and practical insights into the ENSO-wind burst relationship.
• The model accurately captures key ENSO statistics, such as sea surface temperature probability density functions and power spectra.
• This simplified approach highlights the critical role of stochastic wind bursts in driving ENSO variability.