Analyzing the climatic teleconnections of meteorological variables and drought of Kerala, India using coherence differencing approach

Large-scale global climatic oscillations (GCOs) play a vital role in modulating the hydrometeorological patterns across the Globe. Recently, Kerala, the southwest coastal State of India has been increasingly impacted by consecutive extreme weather events highlighting the State’s increased vulnerability to climate variability. This study presents a comprehensive evaluation of multiscale teleconnections between five key hydrometeorological variables: temperature, rainfall and drought (represented using Standardised precipitation index at 3-, 6-, and 12-month scales) and five major GCOs: El Niño Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), Indian Ocean Dipole (IOD), North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation (AMO). The analysis covers a 41-year period (1980–2020) across three major urban cities of Kerala: Trivandrum, Kochi, and Kozhikode, with the help of bivariate and multivariate wavelet coherence analysis to capture the localised and time-varying associations between GCOs and hydrometeorological variables. The study proposes a percentage of significant coherence differencing (PSD) scheme to quantify the relative significance of each GCO in the multivariate framework, addressing the limitations of traditional additive methods. The ENSO consistently emerged as a dominant modulator for all the hydroclimatic patterns across all the cities. However, the addition of AMO and/or IOD with ENSO play variable but significant roles in modulating the rainfall and temperature patterns whereas addition of NAO and/or PDO is found to be influential for drought analysis. The PSD scheme offers a refined approach for understanding climate teleconnections and the study findings underscore the need for location-specific analyses to support climate resilience strategies in monsoon-dependent regions like Kerala.