**4. Discussion**

Other relevant but less repeated conclusions that were found but are not shown in **Table 4** are listed below:


Furthermore, the effects of the co-occurrence of AMO, ENSO, and PDO may be different from those when presented individually. For example, it has been noticed that El Niño events occur more frequently during positive phases of PDO [47, 49] and the most important climate impacts in the country could occur when ENSO and PDO are in phase [7, 16, 77, 78]. Besides, changes in the strength and spatial scale of the precipitation-ENSO teleconnection could be related to SST variability in the North Atlantic [74]. Some authors suggest that the strongest impacts arise when the North Atlantic and the tropical Pacific exhibit opposite anomalies [27, 77]. Additionally, Stahle et al. [60] observed that the response of the June PDSI to the combined ENSO-AMO index is stronger and more widespread in northern Mexico than for the ENSO or AMO indices alone. Hence, contemplating the synergistic effects of oceanatmospheric circulations opens the possibility of making better predictions based on the effect of these circulation systems on terrestrial precipitation [50].

Among possible limitations that the validity of this study could concern, it is important to mention that the selection of only one database could restrict the articles screened, for this reason, the largest digital library of peer-reviewed literature was selected to conduct the review. In addition, to enlarge the examination, manual search was conducted to include some of the most relevant documents that were not encompassed in the Elsevier's Scopus search. Also, when conducting a systematic review, there is always a risk that there would be some papers unavailable in digital databases or documents that miss important keywords in their metadata [86].

Lastly, further research might focus on the teleconnections that have the most divergent conclusions, for instance, those in which ¾ or less authors match conclusions. Examples include summer ENSO conditions in the north, for both phases (El Niño and La Niña), and El Niño conditions in the north during the whole year. Both phases of ENSO might also be studied for the winter season in the center, south, and most of the territory. In addition, PDO+ and AMO conditions in the north could be suggested for further research given the existence of opposite conclusions. Among these studies with divergent findings, the uneven extension of the study area was

found as a commonality. Attention must be paid to the spatial extent considered because interpretation of anomalies in precipitation driven by climatic indices can be interfered by small-scale processes such as localized convection.
