Transcript 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
“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
West African Features examined
for 20-21st century simulations
• 200 hPa zonal windsTropical Easterly Jet(TEJ)
• 700 hPa zonal winds African Easterly Jet
(AEJ)
• Precipitation field
• African Easterly
waves
• Meridional
temperature gradient
• Sea Level pressure
fields.
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