Meaning and mechanism
Normally, trade winds gather warm surface waters to the west, and are linked to upwelling in the eastern equatorial region. The temperature difference between east and west is also connected to atmospheric circulation.
If the trade winds weaken, there could be a change in the supply of cold water from the east and a shift in the structure of the thermocline, leading to warming of the eastern surface layer. This also responds to changes in the distribution of rainfall.
Relationships and conditions
The experiment compares typical surface layer depth, temperature layer, and rainfall conditions according to wind speed. It examines interconnected changes when one condition is altered.
The actual cycles and development of ENSO are influenced by feedback and oscillations, as well as seasonal conditions. The values on the sliders are not actual El Niño assessment indices or future forecasts.
What to observe in the simulation
In weak trade winds, the east warms and the precipitation zone moves east. The opposite is true in strong trade winds.
It is a conceptual state model that interpolates normal, El Niño, and La Niña with continuous trade wind values. The temperature and thermocline depth are virtual values, and the change time is model s. It does not include atmospheric/oceanic feedbacks or actual ENSO standards/cycles/forecasts.
Key relationships and symbols
Trade winds ↑ → western warm water accumulation ↑ · eastern upwelling ↑
| Symbol | Meaning | Unit |
|---|---|---|
| Thermocline | Layer where water temperature changes rapidly with depth | Depth interval |
| Upwelling | Flow of deeper water toward the surface | Direction of motion |
Worked example
What combination appears in La Niña's strong trade winds?
When east to west winds are strong, more warm water accumulates in the west and the thermocline in the east becomes shallower. As the upwelling becomes stronger, the eastern surface becomes colder.
Common misconceptions
- It should not be viewed as an instance where the sea water temperature in the east changes independently, solely due to the phenomenon of El Niño.