What is teleconnection analysis and the ONI in drought studies?
In short: teleconnections are statistical links between drought in a region and large-scale climate patterns such as ENSO, the NAO, PDO, and IOD. The Oceanic Niño Index (ONI) — the three-month running mean of sea-surface-temperature anomalies in the Niño 3.4 region — is the standard measure of El Niño and La Niña. Correlating a drought index with the ONI shows how strongly ENSO drives local drought. DMAP V2.1 includes teleconnection analysis, for example against the ONI.