**6. References**

294 Atmospheric Model Applications

RPC Mean 1948- 1957 1958-1967 1968-1977 1978-1987 1988-1997 1998-2007 RPC1 0.58 1.16 0.70 -0.52 -0.56 -0.94 RPC2 0.24 -0.05 -0.48 -0.22 -0.16 0.61 RPC3 0.03 0.35 -0.25 -0.35 -0.27 0.24 RPC4 -0.10 0.40 0.51 0.41 -0.10 -0.75

RPC Variance 1948-1957 1958-1967 1968-1977 1978-1987 1988-1997 1998-2007 Row Mean RPC1 0.41 0.13 0.29 0.49 0.20 0.46 0.33 RPC2 1.50 0.84 0.93 0.76 1.18 0.41 0.94 RPC3 1.92 1.15 0.32 0.32 1.04 0.98 0.96 RPC4 0.65 0.96 0.38 1.28 1.35 0.37 0.83

After computing oblique PC score correlations (Table 6), only 1 mode pair (RPCs 1 and 4) were significantly correlated (+0.35 for SZS and EANA). Inspection of the associated spatial maps (Figs. 18 and 24) shows Pacific and Atlantic Ocean areas had similar loading patterns.

RPC S1 S2 S3 S4 S1 1.00 -0.19 0.00 0.35 S2 -0.19 1.00 0.13 -0.16 S3 0.00 0.13 1.00 -0.02 S4 0.35 -0.16 -0.02 1.00

RPCA was used to filter the monthly 500 hPa geopotential heights in January and July for 1948 – 2010 to establish the dominant modes of variability over that period. For January, 8 modes, accounting for 70% of the total variance, were extracted. The majority of the patterns that emerged in these analyses had been identified in other studies, published mainly in the 1980's. However, several new patterns emerged in both months and the variance extracted by each pattern showed major shifts when the recent height data were included. RPCs that highlighted subtropical height anomalies were found to be more important when post-1980's data were included and statistically significant linear trends emerged on 4 of the 8 winter patterns with one additional marginally significant pattern. Moreover, the variability of all patterns had marked decadal variation. The July analyses were even more striking as two of the four modes has significant trends in their RPC scores. The leading mode for summer, SZS, extracted a massive 24.9% of the total variance. That pattern was zonally

Column Mean 1.12 0.77 0.48 0.71 0.94 0.56

**3.2.2 Intercorrelation of the time series for the July modes** 

Table 4. Same as Table 1, but for July

Table 5. Same as Table 2, but for July.

Table 6. Same as Table 3, but for July.

**4. Conclusion** 


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