## 3 Results
### Seasonal Features

Table 4: [PERSON]’s correlation coefficients between the monthly mean time series of the number of pixels in each of the clusters or of the entropy and the monthly time series of the Antarctic Oscillation (AAO), the Pacific Decadal Oscillation (PDO), the Quasi-Biennial Oscillation (QBO), the Southern Oscillation Index (SOI) and the Madden-Julian Oscillation (MJO) at ten different longitudes. Correlations were calculated seasonally (December/January/February (DJF), March/April/May (MAM), June/July/August (JJA) and September/October/November (SON)) and for the entire period, i.e., disregarding year or season. Values shown are significant at a 95% confidence level. The QBO index used here consisted of a monthly zonal average of the equatorial zonal winds at 30 hPa. It is therefore the only index that includes a stratospheric meteorological variable. With the exception of the correlation with the entropy all-year long, correlations with the QBO matched the ones with the PDO both in value and in season, i.e., during spring there was an increase both in cluster 1's number of pixels and in the entropy with \"positive\" phases of the QBO (i.e., weak easterlies of westerlies). The results presented here are in agreement with those in [93] who observed that regionally the greatest number of pixels with significant correlations between the ultraviolet reflectivity and the QBO occur during spring. The greatest number of MCCs in South America occurs in spring too [90]. This can be partly understood by dint of the QBO/ENSO phasing [82]. The MJO quantifies the intraseasonal variability in the tropical atmosphere and is known for influencing both the tropical and the extratropical weather patterns. More specifically, the MJO plays a role in modulating the precipitation regime through the interaction between the general circulation with deep convection ([80] and references therein). In particular, the active phase of the MJO had an effect in the activation of large convective cloud systems with temperatures at their top in agreement with the ones in the lower portion of the histograms in Figure 11 ([80] and references therein). The correlations between the MJO and cluster 1's number of pixels occurred during (austral) summer and fall--when the MJO is at its peak [80]-- and all through the year (cf. Table 4). Even though no significant \(\rho\) values were found for the rest of the seasons, it is likely that the significant year-round values are strongly influenced by the contributions from summer and fall since it is in these two quarters when convection is stronger in the SH due to the astronomical forcing. The zonal differences in both the strength and the sign of the correlations were related to the MJO's alternation between its active and suppressed phases across the latitudes it was calculated at, making the strongest positive (negative) \(\rho\) values to take place at 140 \({}^{\circ}\)E (20 \({}^{\circ}\)E). As with cluster 1, the phasing of the MJO can be recalled to explain the year-round correlations with cluster 2's number of pixels across the different longitudes as well, yet the MJO's role in modulating the number of pixels in this cluster was not as strong as with cluster 1's (i.e., the \(\rho\) values were lower). On the other hand, there was a seemingly stronger modulation in cluster 2's number of pixels in winter (spring) when convection was suppressed (active) at 80 \({}^{\circ}\)E (120 \({}^{\circ}\)W). In view of the general agreement of cluster 2 with the cloudiness present in synoptic-scale processes (cf. Figure 12) and their pixels spreading across the entire study region (cf. Figure 8), these results show an apparent connection between the mesoscale and the synoptic scale. Such a relationship between these two different atmospheric scales has been documented for the region (e.g., [94]). The MJO at 70 \({}^{\circ}\)E was the only index that correlated with clusters 3 and 4, in spring and winter, respectively. This could be related to the aforementioned swapping in the number of pixels between these two clusters.