Statistical analysis of rainfall seasonality across South Africa

• Main Author: Roffe, Sarah Jane
• Format: Thesis
• Language: English
• Published: 2019
• Subjects: Rainfall anomalies > South Africa; Rain and rainfall > South Africa; Rivers > South Africa; Antarctic; The Antarctic; Antarc*; Sea ice
• Online Access: https://hdl.handle.net/10539/29571

A Thesis submitted in fulfilment of the academic requirements for the degree of Doctor of Philosophy School of Geography, Archaeology and Environmental Studies University of the Witwatersrand, Johannesburg, October 2019 Straddling the subtropics and mid-latitudes, the climate of South Africa is influenced by the seasonal migration of the Intertropical Convergence Zone, the Antarctic sea ice extent and associated displacement of the Southern Hemisphere Westerlies. As a consequence of this synoptic mechanism, South Africa has a unique rainfall climatology of summer, winter and year-round rainfall zones (SRZ, WRZ and YRZ). Since the first known publication in 1938, much research has attempted to classify the spatial distribution of these rainfall zones. Different methods with different definitions of rainfall seasonality have been applied, and as such the classification of rainfall seasonality is disputed throughout this literature. Unlike research attempting to classify rainfall seasonality, there has been little research investigating how the seasonal characteristics of rainfall have and may possibly change under anthropogenically induced climate change. Across these studies different seasonality metrics have been applied making spatial and cross-study comparisons difficult. This is problematic for South Africa which has a heavy reliance on the seasonal characteristics of rainfall for activities such as agriculture, water resource management and tourism. To address the aforementioned gaps and issues in literature, this research sought to develop a standard approach to quantify, classify and understand rainfall seasonality and the changes thereof. A consistent dataset of daily rainfall and temperature spanning the period of 1987-2016 from 46 weather stations spread across South Africa was applied to objectively test four seasonality metrics which statistically discriminate between SRZ and WRZ conditions. Linear correlation analysis was applied to the annual seasonality quantities to investigate changes in ...