GCM simulations for West Africa: Validation against observations and projections for future change...
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![Page 1: GCM simulations for West Africa: Validation against observations and projections for future change G.Jenkins, A.Gaye, A. Kamga, A. Adedoyin, A. Garba,](https://reader034.fdocuments.in/reader034/viewer/2022051319/5a4d1b5e7f8b9ab0599abf09/html5/thumbnails/1.jpg)
GCM simulations for West Africa: Validation against observations and projections for future
change
G.Jenkins, A.Gaye, A. Kamga, A. Adedoyin, A. Garba, A. Sarr
AF20
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NCAR Climate System Model • Version 1.3 (Gent and Boville, 1998)• Atmosphere 2.8 2.8, 18 vertical levels• Ocean component - variable resolutions 2.3 at the poles,
1.2 at the Equator, 45 vertical levels• Dynamic/thermodynamic Sea ice component• Land surface model (LSM)• Forced by greenhouse gases using starting times of 1870.
Integrated out to 2100 using A1, A2 and B2 scenarios.• CSM has a relatively low climate sensitivity.
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Current Status
• 2003- Analysed NCAR Climate System Model (CSM) version 1.3 A1 scenario for West Africa.
• 2004- NCAR CSM simulations of West Africa : Present-day and 21st Century Anthropogenic Climate change, Kamga et al. under review, JGR-Atmospheres
• 2004- Drive the regional climate model with CSM data
• 2004- Will write up RegCM/CSM for publication
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Climate Change- Climate Variability linkage in West Africa
• Observed – Reduced Rain rates
associated with:– A southward shift in AEJ
(700 hPa)– A weaker TEJ (200 hpa)– Warmer surface temps.
• Can we use observed changes as a fingerprint for future climate and rain rates?
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Reduction in the Area of Lake Chad25000 km2
To 1350 km2
from reduced rainand irrigation
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21st Century Regional Climate Change (Temperature)
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Understanding Future Climate Change in West Africa
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21st Century Regional Climate Change (Precipitation)
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Ensemble Model Approach to Climate Change in West Africa
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Single Model Approach to Climate Change in West Africa
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Single Model Approach to Climate Change in West Africa
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21st century temp./prec. diff
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Temperature (Observations and CCSM)
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Precip. (Observations and CSM)
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CSM and Observed annual Precipitation. comparison
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CSM and Observed annual Temperature comparison
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Observed and simulated Sahelian Precipitation anomalies (20th century)
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Observed and simulated Sahelian Temperature anomalies (20th century)
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Sahelian 21st temp. trends
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Sahelian 21st century Temp. anomalies
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Sahelian 21st century precipitation trends
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Sahelian 21st century Precipitation anomalies
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20th and 21st annual Temp. comparison
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20th and 21st annual Precip. comparison
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Conclusion
• CSM suggest that the region will become:• Warmer by 1.5-2.5C based on SRES scenarios.• Wetter --especially in the Sahel - due to an
increase in low-level moisture (strengthening of monsoon flow).
• Only small changes noted for Easterly waves.• CSM has significant biases in SLP, Surface air
temperatures, precipitation and 200 hpa Zonal winds.
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Future Activities • Downscaling -- running a regional climate model
(RegCM) for present-day and future climates.• Identifying biases in both GCM and regional climate
model simulations.• Publishing results.• Work to reduce biases in GCM/RegCM.• Will use CSM 2.0 and CSM 3.0 data in the future.• Build human scientific capacity for decades of future
research!!
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Future Directions
• Analyze CCSM 2.0/3.0- Biases in Sea level Pressure, upper level winds much smaller.
• Use A1, A2, B2 simulations from new CCSM runs to drive regional climate model.