Table 1 summarizes the PCA results for each study period,
namely, the four seasons and annual period. In general, the first
mode accounted for a substantial part of the total variance, from
35% in summer to 61% in autumn. This first mode accounts for a
spatially coherent variability across the study region, that is, the
loading factors have the same sign across the region (positive or
negative). This mode can be considered as the background coherent
temporal mode of variability in the entire region, to which the
temporal variability represented by the other modes should be
added. In contrast, the second and subsequent modes generally
show areas of positive and negative loadings (dipolar pattern).
Consequently, these modes may be relevant for our balancing
study. In the following sections, we have only analyzed the second
mode for all study periods except autumn, for which both the second and third modes were analyzed. This selectionwas based on
the power fluctuation reduction obtained. Only the aforementioned
modes showed a power fluctuation reduction considerably
greater for the (All) connection than for the (Ref) connection.