A quasi-oscillatory semidecadal cycle in Northern Hemisphere seasonal networks

Area of Science:

• Climate dynamics
• Tropical-extratropical interactions
• Atmospheric and oceanic oscillations

Background:

• The interconnectedness of tropical and extratropical climate modes across seasons and their cumulative effects remain incompletely understood.
• Identifying cyclical patterns in climate variability is crucial for improving seasonal and long-term climate predictions.

Purpose of the Study:

• To investigate the semidecadal cycles within the Indian Ocean Dipole (IOD) and El Niño-Southern Oscillation (ENSO).
• To explore the influence of the Arctic Oscillation (AO) and Asian-Pacific summer monsoons on these tropical climate modes.
• To understand the role of the Atlantic Multidecadal Oscillation (AMO) in modulating decadal climate variability.

Main Methods:

• Time-varying climatological averages were removed to identify semidecadal cycles in IOD and ENSO.
• Regression analysis was used to examine the relationship between Indo-Pacific convective activity and sea surface temperature gradients.
• The Network on Decadal Echo (NODE) was analyzed for quasi-oscillatory characteristics, particularly under different AMO phases.

Main Results:

• A semidecadal cycle was identified in both the IOD and ENSO.
• The spring Arctic Oscillation (AO) and Asian-Pacific summer monsoons showed a strong relationship with convection peaks before and one year after.
• The NODE exhibited semidecadal oscillations, strongly linked to the AO during negative AMO phases, influencing IOD and ENSO states.

Conclusions:

• The study elucidates the AO-monsoon Hadley cell-IOD and AO-Western North Pacific trough-ENSO relationships, offering insights into seasonal network mechanisms.
• Multidecadal, state-dependent oscillatory NODE cycles suggest potential for hemispheric climate accumulation.
• Understanding these interactions is key to predicting seasonal climate variability and long-term climate change impacts.