Figure 2 shows the lagged correlations between
seasonal precipitation anomalies in NVE and the
SST anomalies for the Nino 3 and NATL regions at
0 to 6 months lag. The results indicate that the
influence of these respective ocean basins on
seasonal rainfall in NVE varies with season with
Nino 3 SSTs dominating in DJF and SON with the
NATL region being most influential during JJA.
The correlations are negative for the Nino 3 region
and positive for the NATL region, consistent with
other studies in the region (see Enfield and Alfaro
1999, Giannini et al., 2000).
Figure 2. Zero to 6 month lagged correlations between
rainfall anomalies in NVE region and SST anomalies in
the a) Nino 3 and b) NATL regions. Left-most bar is for 0
lag while successive bars indicate lags increasing by 1
month. Dashed lines indicate statistical significance at
the 95% and 99% confidence levels.
3.3 Seasons with Extreme Rainfall and ENSO
For the JJA and SON seasons we selected
those years where rainfall in NVE was at or above
the 90th percentile (from 1950-1999) for further
analysis. An interesting result for the JJA season
is that 5 out of the 6 cases with greatly enhanced
seasonal rainfall occurred during years when there
was a transition from the warm to cold phase of
ENSO. Our previous results indicated JJA rainfall
in NVE is correlated with anomalously warm SSTs
in the NATL region. Here we see that the oceanic
influence is enhanced when temperatures in the
tropical Pacific are of opposite sign. This is similar
to the result found by Enfield and Alfaro (1999) for
rainfall in the Caribbean and Central America.