Movies illustrating nonlinear teleconnections from ENSO and AO
(additional material supplementing the EGU 2005 conference poster by Wu, Hsieh and Shabbar)


Click image to see this animated GIF movie comparing (a) the linear projection (LP) and (b) the nonlinear projection (NLP) of the El Niño-Southern Oscillation (ENSO) index onto the winter N.Hemisphere sea level pressure (SLP) anomalies (contoured) and the surface air temperature (SAT) anomalies (coloured), i.e. the movie shows the anomalies in the SLP and SAT fields associated with changes in the ENSO index as it swings from one extreme (La Niña, corresponding to cold conditions in the tropical Pacific) to the other extreme (El Niño, warm conditions). (The movie loops continuously, but pauses for a few seconds at the extreme La Niña and El Niño states). The linear projection (i.e. regression) gives a standing wave response in the SLP and SAT anomaly fields as the ENSO index varies, while in the nonlinear projection (performed by a neural network model), the response is not spatially fixed. The presence of substantial response over the Euro-Atlantic region, in the form of a positive "North Atlantic Oscillation" (NAO) pattern (during both extreme La Niña and El Niño) in the nonlinear projection is missing in the linear projection. This shows that there is a nonlinear excitation of the positive NAO pattern by ENSO. In (c) and (d), the LP and NLP of the ENSO index onto the 500 hPa geopotential height (Z500) anomalies (contoured) and the normalized precipitation anomalies (coloured) are shown. [This movie is also available in AVI format].

Click image to see this animated GIF movie comparing (a) the linear projection (LP) and (b) the nonlinear projection (NLP) of the Arctic Oscillation (AO) index onto the winter N.Hemisphere sea level pressure (SLP) anomalies (contoured) and the surface air temperature (SAT) anomalies (coloured). In (c) and (d), the LP and NLP of the AO index onto the 500 hPa geopotential height (Z500) anomalies (contoured) and the normalized precipitation anomalies (coloured) are shown. [This movie is also available in AVI format].


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