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April 2013
Climate Change Projections for African Urban Areas
EGU General Assembly 20013
Ingo Simonis, Francois Engelbrecht, Edoardo Bucchignani, Paola Mercogliano, Mogesh Naidoo
Modelling Physical Processes
General Circulation Models
On a global scale:• Horizontal resolution: 200-
600km • Vertical: 10-20 layers in
atmosphere• up to 30 layers in oceans
Uncertainties
1. Coarse resolution of models relative to the scale of exposure units
2. Many physical processes also occur on smaller scales and cannot be properly modelled Properties must be averaged
3. Various feedback mechanisms, e.g. water vapour and warming, clouds and radiation, ocean circulation and ice and snow albedo…
Uncertainties
1. Coarse resolution of models relative to the scale of exposure units
2. Many physical processes also occur on smaller scales and cannot be properly modelled Properties must be averaged
3. Various feedback mechanisms, e.g. water vapour and warming, clouds and radiation, ocean circulation and ice and snow albedo…
different GCMs simulate quite different responses to the same forcing
Downscaling
Ensemble Simulations
Slide 7
Sing
le M
odel • perturbations of the initial
conditions • to account for the non-linear
dynamics• perturbations of the boundary
conditions • to account for the ‘imperfect’
characterization of the non-atmospheric components of the climate system and also – in case of a regional model – for the uncertainty of the driving global model
• perturbations of the model physics • to account for the uncertainties
inherent in the parameterizations Mul
ti M
odel • to account for the uncertainties
inherent in the models themselves
Ensemble Simulations
Slide 8
Sing
le M
odel • perturbations of the initial
conditions • to account for the non-linear
dynamics• perturbations of the boundary
conditions • to account for the ‘imperfect’
characterization of the non-atmospheric components of the climate system and also – in case of a regional model – for the uncertainty of the driving global model
• perturbations of the model physics • to account for the uncertainties
inherent in the parameterizations Mul
ti M
odel • to account for the uncertainties
inherent in the models themselves
CSIR: Six Models Ensemble for A2 Scenario
CMCC: One Model multiple permutations for A1B
Scenario
60-80km & 8km Resolution Data
60-80km & 8km Resolution Data
http://ict4eo.meraka.csir.co.za/anonftp/CLUVA/
60-80km & 8km Resolution Data
Projected change in annual rainfall and temperature 2040s vs 1960sRobust message across ensemble of an increases in rainfall in the northModerate increase in temp: ~ 2 degrees C by the 2040s
Dar es Salaam
© CSIR 2007 www.csir.co.za
Projected change in rainfall across seasons - 2040s vs 1960s
Median of ensemble projects relatively large increases in rainfall – all seasons except SON (spring)
Dar es Salaam
© CSIR 2007 www.csir.co.za
Time series of temp and rainfall: 1961-2050
* 1961-1970 climate as baseline – 1 ens member shown here
* Temp increase reaches 2.5 degrees C by 2050
* Large shift projected in rainfall – increased variability
Dar es Salaam
60-80km & 8km & 1km Resolution Data
http://ict4eo.meraka.csir.co.za/cluva/