El Niňo

El Nińo: A significant increase in sea surface temperature over the eastern and central equatorial Pacific that occurs at irregular intervals, generally ranging between two and seven years (glossary.ametsoc.org).

Off the west coasts of continents, the Sea Surface Temperature is chilly. Fish love the cold water, especially anchovies.

During El Nińo, SST changes dramatically near Peru

The SST changes have really big consequences for the atmosphere.

This is the development of the most intense El Nińo ever recorded in

Sea Surface Anomalies during 2015

So, what happens during El Nińo? The normal mean pressure features are these: 1. The Subtrop High moves south or weakens 2. Trade winds get weaker or reverse 3. The Aleutian Low strengthens

H H L L For January, 1998, this was the 1000 mb (surface) Mean values Departures from the 30- year mean (Anomalies)

At 250 mb, there were changes caused by the surface pressure and temperature anomalies Mean values Departures from the 30-year mean (Anomalies)

Look at the effect on the 250 mb wind (the Jet Stream!) Mean values Departures from the 30- year mean (Anomalies) The much stronger subtropical Jet Stream explains all the U.S. anomalies

La Niňa

This is the La Niňa event of

This is the latest drought map.

The ENSO cycles vary in length and intensity ~ 6-18 months. There have been several big events in the last 20 years. From

Other circulation patterns and their effects NAO: North Atlantic Oscillation AO: Arctic Oscillation PNA: Pacific/North American (oscillation) PDO: Pacific Decadel Oscillation The figures shown are from

NAO (North Atlantic Oscillation) As the name tells us, this is a pattern located in the North Atlantic Ocean.

From:

AO (Arctic Oscillation) Here we are just interested in the Arctic. From

From:

PNA (Pacific North American Oscillation

PDO (Pacific Decadel Oscillation) Warm Phase Cold Phase

From:

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