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Assessing Global and Regional climate change scenarios for West Africa. AIACC Project AF20. AF20 INVESTIGATORS. Principal Investigator: Amadou Gaye, Senegal Laboratory of Atmospheric Physics, Dakar University Co-investigators: Adamou Garba, Niger

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Assessing Global and Regional

climate change scenarios

for West Africa

AIACC Project AF20


  • Principal Investigator:

  • Amadou Gaye, Senegal

  • Laboratory of Atmospheric Physics, Dakar University

  • Co-investigators:

    • Adamou Garba, Niger

    • African School of Meteorology, Niamey, Niger

    • Andre Kamga , Cameroun

  • ACMAD, Niger.

    • Akintayo Adedoyin, Nigeria

    • University of Botswana

  • Abdoulaye Sarr, SENEGAL

  • Met Service Dakar & LPASF Dakar University

  • Dakar

  • Gregory S. Jenkins, USA

  • Department of Meteorology, Penn State University

Context of West Africa

- West Africa experienced downward reduction in rain amounts

over the last three decades

- Factors potentially responsible for reduced rain amounts :

land-use change, Atlantic and global SST anomalies,

inter-hemispheric SST trends, lower and upper troposphere

wind anomalies and anthropogenic greenhouse forcing

- Changes in the regional climate of West Africa remain uncertain,

especially with respect to rain;

much of the rain is associated with squall lines and

mesoscale convective complexes (MCCs).

Moreover these systems are associated with synoptic-scale easterly waves,

responsible for tropical cyclogenesis in the Atlantic Basin.


1) Using outputs from GCMs to drive a regional climate

model at the lateral boundaries at 6 or 12-hour periods.

- Because of the relatively sharp vegetation gradients and important

orographic features the regional model may provide a different solution

of future climate change relative to GCMs.

- The regional climate model run at 60 km and the

output can be used as input to statistical models for further

downscaling or used as input into hydrologic, economic or agricultural


2) Capacity building in West Africa

- regional and global climate modelling

- analysis of climate processes


- Provide requisite climate change scenarios needed to

undertake vulnerability studies


Statistical & empirical Downscaling of GCM outputs

Interpolation of changes to locations of interest from

nearby GCM grid boxes

1) direct interpolation

2) regressing grid box data using coefficient deduced

from observations at subscale locations

Socio-economic Scenarios


- DT, DP patterns at global scale


Data (site climatic observations)

Regression schemes

DT, DP at local scale

Which GCM to use?

- above normal

- normal

- below normal

Scatterplot of Temperature and Precipitation projections

showing 3 categories of outpouts (2025)


(a) Assess GCM and Reg climate model simulations for present and

future climate states in order to examine processes that bring about

new climate.

Evaluate GCM scenarios based on given emission scenarios during the

20th and 21st century, identifying strengths and weaknesses of GCM

simulations on seasonal, annual and decadal time-scales for West Africa.

(b) Determine whether these changes are realistic given our current

understanding of the West African Climate system.

(c) Provide model outputs to examine how potential changes in

climate might affect key sectors on national and regional scales



1- Evaluation of mean states (current climate)

2- Evaluation of model variability (current climate)

3- Evaluation of changes in the mean state due to

anthropogenic GhG between 20th and 21 sh century

RCM SIMULATIONS undertaken by :

- MM5 v3 modified & land surface package (LSX)

and(?) Genesis (surface hydrology and energy budget)

- RCM driven at lateral boundaries by 6 and 12h data

from CCSM and emission scenario (SRES A1, ….)



zonal wind at 700 hPa simulated by MM5; the simulations show

little discrepancies in the position of the AEJ

Evaluation of model variability and

changes in mean states

Present var

Future var

Present changes

Future changes



Long-term trend (1848-2000) of precipitation using monthly

rain gages data (Senegal) and comparison with the Gulf of Guinea

Focus on 4 stations (West, North, South,East)


- Capacity building (human and infrastructure)

- linkage with other teams (AF07)

-contribution to National communication

(members of Senegal and Botswana National CC committees)