What happens to the easterly trade winds during El Niño?
During an El Niño event, the easterly trade winds converging across the equatorial Pacific weaken. The strengthening and weakening of the trade winds is a function of changes in the pressure gradient of the atmosphere over the tropical Pacific.
What kind of trade winds Does El Niño have?
The El Niño signal is evident in the eastward-blowing winds in the tropical western and central Pacific. Winds near the equator (5° North to 5° South) blew more forcefully from west to east in the western and central Pacific; meanwhile, the easterly (east to west) trade winds weakened near the Americas.
Are El Nino and La Nina trade winds?
During normal conditions in the Pacific ocean, trade winds blow west along the equator, taking warm water from South America towards Asia. To replace that warm water, cold water rises from the depths — a process called upwelling. El Niño and La Niña are two opposing climate patterns that break these normal conditions.
Do trade winds increase during El Niño?
El Niño Events: results from weakening easterly trade winds. The easterly trade winds are driven by a surface pressure pattern of higher pressure in the eastern Pacific and lower pressure in the west. The weakened trade winds allow warmer water from the western Pacific to surge eastward, so the sea level flattens out.
Why are the easterly trade winds key ingredients in ENSO?
The persistent easterly trade winds are key ingredients of ENSO, because they push warm water toward the western Pacific. Because this large pool of warm water is pushed towards the western Pacific, the atmosphere above the ocean is heated, causing favorable conditions for convection and precipitation.
What happens to air pressure during El Niño?
The Southern Oscillation is a change in air pressure over the tropical Pacific Ocean. When coastal waters become warmer in the eastern tropical Pacific (El Niño), the atmospheric pressure above the ocean decreases.
What is the main difference between El Niño and La Nino?
El Niño refers to the above-average sea-surface temperatures that periodically develop across the east-central equatorial Pacific. It represents the warm phase of the ENSO cycle. La Niña refers to the periodic cooling of sea-surface temperatures across the east-central equatorial Pacific.
What happens to the trade winds during La Niña?
During La Niña conditions, the easterly trade winds near the equator get even stronger than they usually are. Stronger winds push surface water into the western Pacific. As the event develops, the cooled waters cause the winds to strengthen even further, which can cause the waters to cool even more.
How does trade winds affect El Niño?
During El Niño, when the trade winds are weak or even occasionally reverse themselves, the amount of cold water that comes to the surface is reduced. Warm waters in the west Pacific Ocean slosh to the east. Now there is a large area along the equator where ocean temperatures are above normal.
What causes stronger trade winds?
This is called the Coriolis Effect. The Coriolis Effect, in combination with an area of high pressure, causes the prevailing winds—the trade winds—to move from east to west on both sides of the equator across this 60-degree “belt.”
Why do trade winds weaken in El Niño?
During an El Nino, when the warm water moves eastward towards South America (along the thermocline, and reducing the equatorial upwelling), they weaken that gradient, and sometimes event reverse it. As that E-W SST gradient gets weaker, the trade winds get weaker.
What happens to the trade winds during an El Nino?
The air-sea interaction that occur during an El Niño event feed off of each other. As the pressure falls in the east and rises in the west, the surface pressure gradient is reduced and the trade winds weaken.
What happens when the easterly trade winds weaken?
The easterly trade winds are driven by a surface pressure pattern of higher pressure in the eastern Pacific and lower pressure in the west. When this pressure gradient weakens, so do the trade winds. The weakened trade winds allow warmer water from the western Pacific to surge eastward, so the sea level flattens out.
How does El Nino affect the western Pacific Ocean?
The ocean is some 60 cm higher in the western Pacific as the result of this motion. The water and air are returned to the east. Both are now much cooler, and the air is much drier. An El Niño episode is characterised by a breakdown of this water and air cycle, resulting in relatively warm water and moist air in the eastern Pacific.
When does the El Nino and La Nina cycle end?
El Niño and La Niña episodes typically last 9-12 months. They both tend to develop during the spring (March-June), reach peak intensity during the late autumn or winter (November-February), and then weaken during the spring or early summer (March-June).