Abstract:
Rainfall is a vital hydrologic variable that has a direct and significant impact on the economic development of monsoondominated
state of Kerala in southern India. An effective approach providing accurate prediction of rainfall makes it possible
to take preventive and mitigation measures against natural disasters. In this study, the ensemble empirical mode decomposition
(EEMD)–artificial neural networks (ANN)–multiple linear regression (MLR) hybrid approach is used to forecast
the south–west monsoon (SWM) rainfall of Kerala. The EEMD of SWM rainfall of Kerala resulted in a set of orthogonal
components of specific periodic scale. The non-linear components are identified and separately modeled using ANN and rest
of the components are modeled using linear regression to get their values at a specific time t. Finally, the predicted modes
are recombined to get the forecasts of a generic time t. The SWM rainfalls of 1871–1972 are used for model calibration and
forecasts are made sequentially for 1973–2014 period, which clearly demonstrated its efficacy in handling non-linear part of
SWM rainfall data with a predictive skill of 0.65 for validation data. Further, by considering a dataset of 1961–2014 period,
this study has investigated the possible teleconnection of SWM rainfall of Kerala with the Indian Ocean dipole (IOD) using
the cross-correlation and EEMD-based time-dependent intrinsic correlation (TDIC) analyses. Apart from the strong correlation
in the trend component, the analysis has proved the dominancy of negative association of IOD with SWM of Kerala
in different process scales with strong positive association at localized time spells. The forecasting strategy demonstrated
in the study and the evidence of IOD–SWM rainfall link are an amendment to the efforts for improving the predictability
of SWM rainfall in Kerala.
