Climate modelling - future developments and challenges in southern Africa
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Climate modelling – future developments
and challenges in southern Africa
Mavhungu Muthige1,3 and Francois Engelbrecht1,2,3,4
1. CSIR Natural Resources and the Environment
2. NWU - Unit for Environmental Sciences and Management
3. School of Geography, Archaeology and Environmental Sciences,
University of the Witwatersrand, Johannesburg, South Africa
4. Centre for Coastal Paleosciences – Nelson Mandela Metropolitan
University
Climate modelling in and for Africa: key
issues and opportunities
• CORDEX ensemble: largest set of detailed projections ever generated
for Africa – new opportunities for uncertainty analysis
• More process-based studies are needed (e.g. changes in tropical
cyclone tracks, East African monsoon system)
• Data processing and bias-correction for an enhanced application
modelling effort (e.g. crop modelling, hydrological modelling)
• Estimation of climate change costs (using regional projections – e.g.
new WFP project)
• Model development: cloud-resolving models
• Model development: coupled regional models (e.g. VRESM at CSIR)
• Supercomputing and connectivity in Africa
Climate Change and
Tropical
Cyclones+Lows
Model projected change
in tropical cyclone and
tropical low frequencies
over the southwestern IO
and southern Africa, for
2071-2100 relative to
1961-1990.
Malherbe et al. (2012)
Climate Dynamics
© CSIR 2007 www.csir.co.za
Zooming in over African countries using CSIR
climate modelling: Mozambique
CCAM applied in
stretched-grid mode
Strong stretching
(s=0.133) provides a
resolution of about 8 km
over the high-resolution
panel
8 km simulations nudged
in lower resolution
CORDEX simulations
1 km resolution
simulations over of 200 x
200 km^2 nudged within
8 km res simulations
C160 stretched-grid with 8 km horizontal
resolution over a domain of about 1500 x 1500
km^2, centered over Beira
Simulated 1961-1990
climate over
Mozambique (8 km
resolution)
© CSIR 2007 www.csir.co.za
Projected futures
for Mozambique (8
km resolution) 2021-
2050 relative to
1961-1990
New CSIR NRE-BE project
on climate change and rural
road infrastructure makes
use of these projections
Engelbrecht, Le Roux et al.
(2016) In preparation
© CSIR 2007 www.csir.co.za
Detailed CCAM projections over Cape Town
CCAM applied in
stretched-grid mode
Strong stretching
(s=0.133) provides a
resolution of about 8 km
over the high-resolution
panel
8 km simulations nudged
in lower resolution
CORDEX simulations
1 km resolution
simulations over of 200 x
200 km^2 nudged within
8 km res simulations
C160 stretched-grid with 8 km horizontal
resolution over a domain of about 1500 x 1500
km^2, centered over Cape Town
Detailed CCAM projections over Cape Town
CCAM applied in
stretched-grid mode
Strong stretching
(s=0.017) provides a
resolution of about 1 km
over the high-resolution
panel
1 km res simulations
nudged in 8 km res
simulations
1 km resolution
simulations over of 200 x
200 km^2 nudged within
8 km res simulations
C160 stretched-grid with 8 km horizontal
resolution over a domain of about 1500 x 1500
km^2, centered over Cape TownCCAM simulated 1000 hPa streamlines and 10 m wind speed (top) for 1971- 1981 (top) and projected changes in wind speed for 2071-2080 relative to 1971-1981 (bottom) for the ACCESS1-0 and CCSM4 downscalings, over the 1 km resolution domain centred over Cape Town. Units are m/s. (New CSIR+partners project on climate change over African cities – African Development Bank funded)
CCAM 8 km resolution
simulations over Cape
Town
Simulated low-level winds
are shown for June 1986
Analysis of projected
changes in monthly
averages as well as
extreme wind events to
be presented in CSIR
report
CSIR-CHPC
© CSIR 2007
www.csir.co.zaDevelopment of the first African-based ESM
• Development of a CGCM based in South
Africa with world-leading skill in
representing African and southern
hemisphere climate processes
• Application of the new model to perform
novel studies of African climate dynamics,
processes and variability
• An original African-led contribution to
CMIP6 and AR6 of the IPCC, using a
CGCM never applied in CMIPs before
• High-resolution global model projections for
the 21st century for impact analysts,
regional climate modellers (CORDEX),
application modellers and decision-makers
The Variable-resolution in Africa.
Earth System Model: A • The generation of a world-class cadre of
CSIR-CSIRO collaboration earth system modellers, living and working
in Africa.VRESM component models
• Atmosphere: Variable-
Cubic Atmospheric Model
(VCAM) of the CSIRO
(same physics as CCAM)
• Ocean: Variable-cubic
Ocean Model (VCOM) of
the CSIR
• CSIR Sea-ice: Based on
Petit and Norro (2000) Plot of the equi-angular gnomonic-cubic grid used by
both VCAM and VCOM. The common grid simplifies
• Land: CSIRO Atmosphere coupling and improves efficiency for eddy
Biosphere Land Exchange permitting/resolving spatial scales
System (CABLE)
• Dynamic river routing:
CSIRO-CSIR • Ocean Biochemistry: PISCES from FranceTowards VRESM: ocean model
development – MPI, mixing and sea-ice
More extensive VCOM tests to
follow – MPI version for massive
parallel processing is underway.
Focus on the parameterisation of
sub-mesoscale eddies in the
southern Ocean.
Stretched-grid regional coupled
version to focus on Benguela
upwelling and the Agulhas
current under climate change.
13Towards VRESM: dynamic river routing and
fresh water fluxes
CSIR is further developing the
CSIRO river routing scheme.
Coupled dynamic hydrology
based on Manning’s formula for
river widths.
Fresh-water fluxes into VCOM is
the main VRESM objective.
Figure shows river water depth
(m) in a 50 km resolution
simulation.
14Conclusions and some near-future plans:
• VRESM (VCOM-VCAM-CABLE-CSIR_ice_rivers) under development towards AR6
and CMIP6
• Stretched-grid mode offers flexible regional-coupled model
• Benguela upwelling + Sc cloud decks + biomass burning aerosols (~ 20% of global
emissions) + tree-grass-fire dynamics in the African savannah + climate change and
feedbacks + climate sensitivity + CMIP5 SST biases = potential CORDEX
FLAGSHIP project. This has been proposed within CORDEX Africa and by a 7-
institute consortium.
Meteosat IR
satellite image
2016-05-15
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