Trend Analysis of Rainfall in Southern Kerala Based on Empirical Mode Decomposition

This study proposes an alternative approach for estimating the short term trend of rainfall southern Kerala, India using Empirical Mode Decomposition (EMD). The annual, monsoon and post-monsoon rainfall data for the recent 30 year period (1983-2012) from 8 stations pertaining to four southern Kerala districts were temporally decomposed and the trend components were extracted. The results were compared with the classical linear trend fitting and traditional Sen’s slope and Mann-Kendall statistics. EMD is successful in capturing inherent non-linear trend of dataset, which cannot be estimated by the traditional approaches. The study showed a consistently increasing trend of annual, monsoon and post-monsoon rainfall at Cherthala station. Monsoon rainfall records of all stations except Cherthala showed a decreasing trend, while post-monsoon rainfall of 5 stations showed an increasing trend and annual rainfall of three stations showed a decreasing trend. The EMD method also depicts the specific shape of trend which is successful in capturing the recent change points of inherent trend in different datasets. EMD based decomposition showed major reduction of annual and postmonsoon rainfall from Alappuzha station and that in post-monsoon rainfall of Kollam and Thiruvalla stations since 2000 (∼). The present study gives broad inferences on changing climate of southern Kerala in the recent past.