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

GCM Scenarios for Regional Studies over West Africa

Gregory S. Jenkins

Department of Meteorology

Penn State University



“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



A1B scenario change is very low”



Objectives of presentation
Objectives of Presentation change is very low”

  • -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
21st century temp./prec. diff change is very low”


West african features examined for 20 21st century simulations

200 hPa zonal winds- Tropical Easterly Jet- (TEJ) change is very low”

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 CCM) change is very low”


Precip observations and ccsm
Precip. (Observations and CCSM) change is very low”


700 hpa aej simulations
700 hPa AEJ simulations change is very low”


African easterly waves
African Easterly Waves change is very low”

  • 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 u,v spectrum change is very low”


Ecmwf ccsm spectrum of u v
ECMWF/CCSM spectrum of u,v change is very low”


Ccm3 ccsm u v spectrum
CCM3/CCSM u,v spectrum change is very low”


Ccm ccsm observational air temps
CCM/CCSM/Observational Air Temps. change is very low”


Sea level pressure comparison
Sea Level Pressure comparison change is very low”


Sea level pressure difference
Sea Level Pressure Difference change is very low”


Sahara warming
Sahara Warming change is very low”

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
AEJ, precip, shear linkages change is very low”



20 21 century u v spectrum
20-21 century u,v spectrum change is very low”


Conclusion
Conclusion change is very low”

  • 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
Initial Regional model tests change is very low”


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