The Walker circulation is a conceptual atmospheric circulation model that describes air flow patterns in the tropics and their influence on climate. It identifies a zonal overturning circulation across the tropical Pacific Ocean characterized by rising air motion over the western Pacific and sinking air motion over the eastern Pacific.
Causes
The Walker circulation is driven by pressure and temperature differences between the eastern and western tropical Pacific:
- High pressure system over cooler waters in the eastern Pacific
- Low pressure system over warmer waters in the western Pacific
This pressure gradient induces prevailing easterly surface winds.
Impacts on Regional Climate
Fluctuations in the Walker circulation significantly impact regional climate patterns:
- Weakening causes El Niño – reduced upwelling leads to unusually warm eastern Pacific sea temperatures
- Strengthening causes La Niña – increased upwelling amplifies cooler eastern Pacific waters
Influence on the Indian Monsoon
Changes in the Walker circulation can affect the Southwest Indian Monsoon:
- On average, the circulation brings higher pressure over India, suppressing monsoon rainfall
- Increasing temperatures and altered circulation strength in spring linked to monsoon disruptions
This underscores the far-reaching climate teleconnections associated with the Walker circulation.
Key Knowledge Gaps
Ongoing research aims to address knowledge gaps about the Walker circulation such as:
- Quantifying impacts of climate change on circulation strength
- Improving predictive capabilities of its regional climate effects
- Further untangling its relationship with other climate drivers
Enhanced understanding will inform forecasting and climate resilience strategies globally.