Trends and variability of rainfall indices along the south coastal places of South Africa

The study investigated rainfall extremes along South Africa’s southern coast over the past twenty-five years (1995-2020). Observational precipitation data was used from ten stations situated in the climatic zones of South Africa's southern coast. The rainfall time series was utilised to calculate extreme rainfall indices, including the Rainfall Anomaly Index (RAI), Consecutive Dry Days (CDD), Consecutive Wet Days (CWD), and the Standardised Precipitation Index (SPI). The Mann-Kendall (MK) and sequential Mann-Kendall (SQ-MK) test statistics were employed for trend analysis and detection of trend-changing points. The trend detection methods were additionally corroborated by Theil-Sen's (TH) trend approach. The wavelet transform method was employed to analyze the predominant periodicities in the rainfall time series over a period of two and a half decades. Statistical analyses were employed for validation. The results demonstrated that all three quasi-global and reanalysis-based precipitation datasets yielded disparate outcomes at various locations.