The role of natural factors (part 1): addressing on mechanism of different types of ENSO, related teleconnections and solar influence

Abstract

The role of natural factors, mainly the sun, is explored on major tropospheric modes of variability in a holistic way. It formulates a flow chart, depicting coupling in the ocean-atmosphere system, initiated by solar decadal variability that involves El Niño Southern Oscillation (ENSO). Possible mechanisms for Canonic ENSO, Modoki ENSO and Canonic-Modoki ENSO are proposed considering their relevance to the decadal variation of Hadley, Walker circulation and mid-latitude jets. The upper stratospheric feature of the polar vortex is included too. Teleconnections by the ENSO on Indian Summer Monsoon (ISM) with a special emphasis on the later two decades of the last century is discussed. The disruption of usual ENSO-ISM teleconnection during that period is also attended. Subsequent analyses presented some results of solar signature which could possibly trigger different types of ENSO, agreeing with proposed mechanisms of the flow chart. It addressed the changing pattern of ENSO behaviour since the 1970s. The overall study can benefit the modelling community by an improved representation of ENSO in models and a better representation of ISM teleconnection via regional Hadley cell.