Periodicities and ENSO relationships of the seasonal precipitation over six major sub-divisions of India

A spectral analysis of the 1848-1995 (148 year) time series of Sontakke and Singh (1996) representing estimates of summer monsoon (June-September) precipitation amounts over six homogeneous zones (Northwest NW, North central NC, Northeast NE. West Peninsular WP, East Peninsular EP, South Peninsular SP) and the whole of India (AI) revealed significant periodicities in the QBO and QTO regions (2-3 years and 3-4 years) as also higher periodicities, some common to all zones. To study the ENSO relationship, a finer classification of years was adopted. For the All India summer monsoon rainfall as also for all the zones except NE, Unambiguous ENSOW (where El Nino existed and SOI minima and SST maxima were in the middle of the calendar year i.e., May-August), were overwhelmingly associated with droughts and the cold (C) events were associated with floods. For other types of events, the results were uncertain and a few extreme rainfalls occurred even during some Non-events.