Gcm scenarios for regional studies over west africa
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GCM Scenarios for Regional Studies over West Africa. Gregory S. Jenkins Department of Meteorology Penn State University. “Africa is Highly Vulnerable to Climate Change.” IPCC 2001.

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GCM Scenarios for Regional Studies over West Africa

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GCM Scenarios for Regional Studies over West Africa

Gregory S. Jenkins

Department of Meteorology

Penn State University


“Africa is Highly Vulnerable to Climate Change.”IPCC 2001


“Impact of particular concern that are of particular concern to Africa are related to water resources, food production, human health, desertification and coastal zones especially in relation to extreme events.”IPCC 2001


“The overall capacity for Africa to adapt to climate change is very low”

IPCC 2001


A1B scenario


West African Precipitation Anomalies


Objectives of Presentation

  • -Compare NCAR CCM3, CCSM v.1 to NCEP

  • -Identify Biases in models

  • Compare 20-21st century climates of West Africa (5-35N, 20W-40E)

  • CCM3 (Kiehl et al. 1998) - Climatological SSTs

  • CCSM version 1 (Boville and Gent, 1998)


21st century temp./prec. diff


200 hPa zonal winds- Tropical Easterly Jet- (TEJ)

700 hPa zonal winds - African Easterly Jet (AEJ)

Precipitation field

African Easterly waves

Meridional temperature gradient

Sea Level pressure fields.

West African Features examined for 20-21st century simulations


Precip. (Observations and CCM)


Precip. (Observations and CCSM)


700 hPa AEJ simulations


African Easterly Waves

  • African easterly waves have

  • 3-5 day periods (Meridional winds) -Burpee, 1972

  • 6-9 day periods - Diedhiou et al. 1999

  • AEJ is modulated on similar time periods.


ECMWF/CCSM u,v spectrum


ECMWF/CCSM spectrum of u,v


CCM3/CCSM u,v spectrum


CCM/CCSM/Observational Air Temps.


Sea Level Pressure comparison


Sea Level Pressure Difference


Sahara Warming

Why does the Sahara warm more with elevated GHGs?

  • Total warming = increased IR forcing + warm advection (Europe).

  • Feedbacks small

  • Warming shared between Sahara and Europe!


AEJ, precip, shear linkages


Shear and Precipitation differences (1999-2002)


20-21 century u,v spectrum


Conclusion

  • West Africa simulated better in A1 simulations relative to CCM3 but for wrong reasons.

  • AEJ, AEWs better simulated in CCSM v.1

  • 21st century warming in West Africa uncertain because of competing factors of warm advection from Europe and land use change in West Africa.

  • AEJ frequency shifted to longer timescale in 21st century.

  • CCSM v.1 can be used as boundary conditions for regional climate model simulations.


Initial Regional model tests


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