Isolating El NiñoCécile Penland
NOAA-CIRES Climate Diagnostics Center
We present a method of filtering out the predictable ENSO signal from tropical sea surface temperature anomalies that retains interannual var- ability not directly related to the evolution of El Niño. The filter is based on the observations that an initial optimal structure for tran- sient growth usually precedes a mature El Niño SST pattern by about 8 months, and that this structure is dominated by three evolving normal modes with different timescales. By removing El Niño this way, clear interdecadal variability can be identified and analyzed. In this talk, we identify two of these interdecadal signals: a parabolic trend affect- ing SSTs in most of the tropical strip, and the tropical Atlantic dipole.
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