Spatiotemporal variability analysis of standardized precipitation indexed droughts using wavelet transform

Abstract

Statistical drought characterization is critical for drought studies within the multivariate temporal and frequency domains. An efficient drought management can result in improved drought preparedness and risk management. In this study, Standardized precipitation indices (SPIs) over various timeframes were derived using precipitation data. The historical data for the hydrological stations and meteorological stations in Sabah and Sarawak, Malaysia were courtesy of the Department of Irrigation and Drainage, Malaysia. Based on the SPI index, the meteorological drought trends, periodicities, and the turning points were analysed using the Mann-Kendall (MK) test, Spearman rho (SR) test, sequential Mann-Kendall (SQMK) test, k-means clustering algorithm, and the Continuous wavelet transform (CWT). The MK and SR test were applied on a decade interval, for a period of years from 1989 to 2018. According to the findings, it was observed that there was a declining tendency shifting from the east to the west in Sabah, whereas in Sarawak, there was observed a declining trend across the state, particularly in its central area. The underlying trend of the droughts in Sabah reveals that the dominant periodicity of the SPI series that persisted throughout the study period at the Sabah stations varied between 2.5 and 5.5 years. However, the periodicity in Sarawak did not vary as much as it did in Sabah. The wavelet coherence analysis also reveals that significant coherence between SPI and climatic indices occurred intermittently for shorter periodicities. Furthermore, the longer dominating periodicities were shown to be associated with one or more climate phenomena.