Characterizing warm-ENSO variability in the equatorial Pacific: An OLR perspective
Andrew M. Chiodi, NOAA/PMEL/JISAO, Seattle, WA; and D. E. Harrison
We show that space-time smoothed outgoing longwave radiation (OLR) indices of equatorial Pacific seasonal variability can give an interestingly different perspective on El Nino than is obtained from sea surface temperature (SST) indices or the Southern Oscillation index (SOI.) In particular, the index defined by averaging over an eastern central region exhibits strongly event-like character; more so than in any other El Nino-Southern Oscillation (ENSO) warm-phase index known to the authors. We suggest that the years identified as events by this OLR index deserve particular recognition, and it is noteworthy that they are all conventionally agreed to be ``El Nino'' years. Although the historical record for OLR is much shorter than for SST or SOI, OLR offers a direct connection to anomalous atmospheric heating. Results presented suggest that anomalous tropical atmospheric heating drives substantial mid-latitude atmospheric anomalies in the years with these OLR events. Other years, whose ENSO-status differs depending upon the index favored, are not particularly distinctive from an OLR perspective and the evidence for tropically driven mid-latitude atmospheric anomalies in these years is less clear. Thus, a case could be made that either they do not deserve special classification or that they should be identified as different from the distinctive conventional El Nino years.
Session 7A, Global dynamics and processes - II
Tuesday, 13 January 2009, 3:30 PM-5:45 PM, Room 129A
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