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Sunday, July 12, 2009

Similarities of the Multiyear Periods Following Significant El Nino Events Since 1970

I’ve moved to WordPress.  This post can now be found at Similarities of the Multiyear Periods Following Significant El Nino Events Since 1970
The 1982/83 and 1997/98 El Nino events are considered the significant ENSO events of the 20th century. Their peak SST anomalies stand above all others. Refer to Figure 1. Well…maybe not. As Karl reminded in the El Nino – same but different thread at WattsUpWithThat, the 1972/73 El Nino came in a close third.

Figure 1

Figure 2 is a 150-month-long comparison of NINO3.4 SST anomalies for the 1972/73 and 1997/98 El Nino events and for the decades or so following them. With the exception of the upswing at the end of the 1972/73 El Nino (purple) curve and the downswing at the end of the 1997/98 El Nino (brown) curve (the upswing and downswing are the 1982/83 El Nino and the 2007/08 La Nina, respectively), the two curves of the secondary upsurges in NINO3.4 SST anomalies are remarkably similar.
Figure 2

The explosive eruption of El Chichon in 1982 minimized (eliminated?) the heat transport from the 1982/83 El Nino event. This can be seen in an MSU TLT Time-Latitude Plot from RSS, Figure 3. So for this post, we’ll consider the 1982/83 El Nino to be dysfunctional and exclude it from this post.
Figure 3

And soon after the effects of the volcanic aerosols from El Chichon subsided, the 1986/87/88 El Nino occurred. Referring back to Figure 1, the SST anomalies of the 1986/87/88 El Nino did not peak as high as the 1972/73 and 1997/98 El Nino events, but the 1986/87/88 El Nino lasted through the entire year of 1987. The end result, there was a noticeable redistribution of heat from the 1986/87/88 El Nino, Figure 4. So in that respect, the 1986/87/88 El Nino was also a significant El Nino.
Figure 4

In Figure 5, I’ve added the NINO3.4 SST anomalies of the 1986/87/88 El Nino to the 150-month-long comparison with the 1972/73 and 1997/98 El Nino events. The 1986/87/88 El Nino also created a multi-year secondary surge in NINO3.4 SST anomalies that was similar in scale to the other two events.
Figure 5

Smoothing the three curves with 25-month running-average filters, Figure 6, helps illustrate the similarities in the three curves.
Figure 6


From 1970 to present (and excluding the 1982/82 El Nino), are the lesser El Nino events that occurred after the significant El Nino events of 1972/73, 1986/87/88, and 1997/98 simply aftereffects?


HADISST anomaly data is available through the KNMI Climate Explorer:

I cut Figures 3 and 4 from Figure 13 in my post RSS MSU TLT Time-Latitude Plots...

The RSS MSU TLT Time-Latitude Plot without my notations is available from RSS here (their Figure 8):

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