Browsing by Author "Reason, Chris J C"

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    Eastern South African hydroclimate over the past 270,000 years
    (2016) Simon, Margit H; Ziegler, Martin; Bosmans, Joyce; Barker, Stephen; Reason, Chris J C; Hall, Ian R
    Processes that control the hydrological balance in eastern South Africa on orbital to millennial timescales remain poorly understood because proxy records documenting its variability at high resolution are scarce. In this work, we present a detailed 270,000 year-long record of terrestrial climate variability in the KwaZulu-Natal province based on elemental ratios of Fe/K from the southwest Indian Ocean, derived from X-ray fluorescence core scanning. Eastern South African climate variability on these time scales reflects both the long-term effect of regional insolation changes driven by orbital precession and the effects associated with high-latitude abrupt climate forcing over the past two glacial-interglacial cycles, including millennial-scale events not previously identified. Rapid changes towards more humid conditions in eastern South Africa as the Northern Hemisphere entered phases of extreme cooling were potentially driven by a combination of warming in the Agulhas Current and shifts of the subtropical anticyclones. These climate oscillations appear coherent with other Southern Hemisphere records but are anti-phased with respect to the East Asian Monsoon. Numerical modelling results reveal that higher precipitation in the KwaZulu-Natal province during precession maxima is driven by a combination of increased local evaporation and elevated moisture transport into eastern South Africa from the coast of Mozambique.
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    Return period of extreme rainfall at George, South Africa
    (2007) Melice, Jean-Luc; Reason, Chris J C
    The torrential rains of August 2006 in the southern Cape of South Africa were the most intense observed in the region. Here we use the longest-available daily rainfall series at George (from 1941 to 2006), in the vicinity of which the most destructive floods were observed, together with an extreme value model to estimate the return period of such an extreme event. According to this model, the greatest annual maximum daily rainfall of 230 mm, observed at the town on 1 August 2006, has a return period of 1222 years, whereas the second-largest observed annual maximum daily rainfall (132 mm in September 1964) has a return period of 23 years. This shows that the August 2006 extreme rainfall at George can be considered as a particularly rare event.