Analyzing the Hydroclimatic Teleconnections of Summer Monsoon Rainfall in Kerala, India, Using Multivariate Empirical Mode Decomposition and Time-Dependent Intrinsic Correlation

This letter presents an alternative approach for investigating the teleconnections of summer monsoon rainfall in the state of Kerala, India, with four prominent climatic oscillations in multiple time scales based on multivariate empirical mode decomposition (EMD) (MEMD) and time-dependent intrinsic correlation (TDIC). First, the multivariate data set constituting summer monsoon rainfall time series and the climate oscillations such as the Quasi-Biennial Oscillation, El Niño Southern Oscillation (ENSO), Atlantic Multidecadal Oscillation, and Equatorial Indian Ocean Oscillation are decomposed to several rotational modes by employing MEMD. To capture the associations in shorter time spells, the TDIC method is employed, in which the sliding window is adaptively fixed based on instantaneous periods obtained by the Hilbert transform of the obtained modes. From the analysis, it is found that the strength and nature of association between summer monsoon rainfall and the climate oscillations vary with time scales and time spells. The performance of MEMD-based TDIC analysis is compared with that of EMD-based TDIC, and it was found that the former one well captured the direct correlation between ENSO and summer monsoon rainfall in the 1997-1998 period and the opposing correlation in the 2002-2003 period, while the latter approach failed to capture such associations properly.