Fig. 3: Causal links between the ISMR and AMO in the presence of other potential drivers using the PCMCI+ causal inference algorithm.

a Causal links between the ISMR and the AMO (NA SST), the ENSO (Nino), the NAO, the PDO, the At-Nino and the IOD on seasonal time-scales based on monthly anomalies of the indices for MJJASO season during the period, 1871–2017 obtained using the multivariate causal framework at 95% alpha level. Monthly anomalies of SST are computed from COBE SST2, Mean sea level pressure from NCEP 20Cv3 and ISMR from Parthasarathy data. b The seasonal causal link between NA SST and ISMR is a result of causal links between the NA SST, the NAO, the BV, the Indian upper level vorticity (IUV) and the Indian lower level vorticity (ILV) (see text for definitions) on intraseasonal time-scales with daily intraseasonal filtered anomalies of indices using a 7-day moving average. The indices for the JJAS season from 1982 to 2010 are detrended. The nonlinear causality from PCMCI+ are shown as arrows, with strength of contemporaneous association (link strength) represented by arrow color (+ve red and –ve blue), while node color represents the node auto-correlation strength. The curved lines represent a time-lagged causal relation, which is represented by the numbers (lag in months), while the straight lines show the contemporaneous relationship between dependencies, with or without orientation. The color represented in the schematics of various processes (other than nodes and connector arrows) in the map is just for illustration purposes only.