ENSO (El Nino Southern Oscillation) ENVS

Normal Conditions: West Pacific Warm Pool

El Nino Conditions

El Nino forecasting Careful monitoring of – Oceanic temperatures (satellites) – Strength of trade winds sometimes it works – sometimes it doesn’t

How to measure sea surface temperatures (old school) automated buoys (get spot measurement, often temperature profile) → buoy arrays temperature recorders in the water intakes of big ships → variable locations, sampling depth might not be constant (loaded vs. empty vessel) but greater geographical coverage

How to Measure Sea Surface Temperatures from Satellites? infrared radiation problem: cannot see through clouds, aerosols electromagnetic radiation at other wavelengths – microwave radiation (can see through clouds and aerosols, but is scattered by raindrops)

how to measure ocean temperature at depth ? warm water is less dense → takes up more space (floats on top of colder water) sea surface rises 50 m of 1C warmer water raises sea surface by approximately 1 cm after lots of correlations, corrections and other trickery → get temperature distribution with depth

Historical variations Red: El Nino Blue: La Nina

How can you Reconstruct ENSO Cycles ? Expressed as: – sea surface temperature anomalies – air temperature, atmospheric pressure anomalies in Pacific – precipitation ? – economic effects ? – climate effects outside equatorial Pacific?

Where is atmospheric pressure high, where is it low ?

source:

DarwinTahiti

The Southern Oscillation Index (SOI) expresses difference in barometric pressure between Australia (Darwin) and Thaiti several ways to calculate P diff = MSLP Thaiti - MSLP Darwin sustained negative values: El Nino sustained positive values: La Nina

Source: Commonwealth of Australia 2006, Bureau of Meteorology (ABN ) (accessed 3/13/06)

ENSO Cycles El Nino – La Nina phenomenon is cyclical Note timescales involved How rapidly does atmosphere change ? How rapidly do oceans change ? Oceans are a good place to look for drivers of short term climate change