Identification of periodicity in the relationship between PDO, El Niño and peak monsoon rainfall in India using S‐transform analysis

Abstract

AbstractPeak monsoon rainfall (PMR) data have been examined 135 years for five rainfall regions of the Indian subcontinent. S‐transform analysis was used to analyse the non‐stationarity in the periodicity of rainfall patterns over the study period. The results of the analyses revealed the presence of a 2–3 year cycle corresponding to the El Niño cycle, with periodic strengthening at the decadal scale across most of the regions as well as at the all India level. Further examination revealed that the 2–3 year cycle usually strengthened a few years before the beginning of the cold phase of the Pacific Decadal Oscillation (PDO), and this cycle continued through most of the cold phase. This 2–3 year cycle, however, was almost negligible during the subsequent warm phase of PDO for all regions except the central northeast region. Such a periodic strengthening of the periodicity in PMR during the cool phase of PDO is possibly caused by the differences in temperatures in different parts of the Pacific Ocean. Copyright © 2010 Royal Meteorological Society