ACCESS Theme 1 – Weather and Climate Variability: Fundamentals, Predictability and Application

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willem                               mathieu

Dr Willem Landman (CSIR)                        Professor Mathieu Rouault (UCT)

(walandman @ csir.co.za)                            (mathieu.Rouault @ uct.ac.za)


Student statistics 2013: Honours (4); Masters (9); PhD (12)

Partner institutions: UCT, Monash-SA, U Zululand, WITS, SAWS, CSIR, ARC, U Limpopo, UP, UKZN

See ACCESS Research Compendium 2013: Pages 3-17 for details.


The focus of this theme is the variability of southern African weather and climate on timescales from short-range weather forecasting (beyond 12 hours), through to climate forecasting beyond two years, but less than a decade. This theme is subdivided into three main focus areas: investigating the underpinning science of weather and climate variability and predictability through theoretical research of observational and model data; developing models and systems for the production of weather and seasonal forecasts for the SADC region; and, finally, applying and tailoring these forecasts to suit user needs and dissemination of forecast products. Advancing our understanding of southern African weather and climate variability and change can be achieved through an Earth Systems Science observation network, monitoring key areas and conducting dedicated experiments at land and sea. This focus area strives to ensure that the observations required to meet national needs for weather and climate data are identified, obtained and made widely available. Its goal is to provide continuous, reliable and comprehensive data and information on the state and behaviour of the climate system of southern Africa and its surrounding oceans, including its physical, atmospheric, oceanic and hydrological processes. Numerical weather prediction (NWP) models resolving atmospheric processes more explicitly at a higher horizontal resolution contribute to the recent increased accuracy of short-range predictions. These models can provide sufficient warning of imminent national weather-related disasters and high impact weather (floods, extreme temperatures and storms), as well as meteorological variables that can supply input to special applications models (air quality, flash flood guidance, fire danger, wave modelling and electricity demand models) — vital for decision making. The seasonal-to-inter-annual variability of rainfall and temperature anomalies over southern Africa is also predictable. Most of the seasonal forecast skill is a result of the ability of these models to capture the influence of the El Niño Southern Oscillation (ENSO) events over the region, but improved predictability can be achieved through the development of state-of-the-art Earth System models. The South African end-users of weather forecasts have been largely supplied with skilful forecasts of probabilities indicating the likelihood of above or below normal rainfall and temperature for a coming season. Delivery and uptake of useful climate variability information is a substantial challenge, and in South Africa the resources currently invested in the development of physical systems capable of providing reliable information on future outcomes far outweigh those dedicated to the packaging of such information to end-users. This focus area addresses this deficiency by supplying additional forecast information products for the benefit of end-users, including outputs from applications models, as well as derived products (seasonal onset, cessation and drought severity) and probabilities of crossing different risk thresholds.