Assessing Global and Regional climate change scenarios

for West Africa

AIACC Project AF20

AF20 INVESTIGATORSPrincipal Investigator:

Amadou Gaye, SenegalLaboratory of Atmospheric Physics, Dakar University

Co-investigators:Adamou Garba, Niger

African School of Meteorology, Niamey, Niger

Andre Kamga , CamerounACMAD, Niger.

Akintayo Adedoyin, NigeriaUniversity of Botswana

Abdoulaye Sarr, SENEGALMet Service Dakar & LPASF Dakar UniversityDakar

Gregory S. Jenkins, USADepartment of Meteorology, Penn State University

- 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.

Context of West Africa

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 models.

2) Capacity building in West Africa- regional and global climate modelling- analysis of climate processes

GOALS

- Provide requisite climate change scenarios needed to undertake vulnerability studies

Methods

Statistical & empirical Downscaling of GCM outputs

PREVIOUS WORK

Interpolation of changes to locations of interest from nearby GCM grid boxes

1) direct interpolation

2) regressing grid box data using coefficient deducedfrom observations at subscale locations

Socio-economic Scenarios

Magicc/Scengen

- MSL - DT, DP patterns at global scale

Data (site climatic observations) Regression schemes

DT, DP at local scale

Mali Grid box for GCM at 5°x5° resolution

-17° -16° -15° -14° -13° -12°

longitude

12°

13°

14°

15°

16°

latit

ude

-17° -16° -15° -14° -13° -12°

longitude

12°

13°

14°

15°

16°la

titud

e

-17° -16° -15° -14° -13° -12°

longitude

12°

13°

14°

15°

16°

latit

ude

sensib ilité = 1 ,5°C

sensibilité = 2 ,5°C

sensibilité = 4 ,5°C

Horizon 2025

-20

-15

-10

-5

0

5

10

15

0 0,5 1 1,5 2 2,5

Delta_T (°C)

Del

ta_P

(%)

Scatterplot of Temperature and Precipitation projections showing 3 categories of outpouts (2025)

- above normal- normal- below normal

Which GCM to use?

(a) Assess GCM and Reg climate model simulations for present andfuture climate states in order to examine processes that bring aboutnew 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

PRESENT OBJECTIVES

LOCALEFFECTS

TROPICAL TROPOSPHERIC DYNAMICS ALREADY

DEVELOPED

DEVELOPMENT OF A MESOSCALE MODEL FOR TROPICAL SYSTEMS

RUNNINGA REGIONAL CLIMATE

MODEL(MM5 v3)

A REALISTIC WESTERN AFRICA REGIONALCLIMATE MODEL THAT MAY ADDRESS ISSUES LIKE:

Effects of climate change on water resources Effects of climate change on agriculture Effects of climate change on health-related Effects of climate change on energy sources

GCM(CCSM/NCAR)

Flow shart of methodsFlow shart of methods

METHODOLOGY

GCM SIMULATIONS

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

Evalutation of Mean State

observed

simulated

zonal wind at 700 hPa simulated by MM5; the simulations showlittle discrepancies in the position of the AEJ

Evaluation of model variability and changes in mean states

Present var

Future var

Present changes

Future changes

present

future

Long-term trend (1848-2000) of precipitation using monthly rain gages data (Senegal) and comparison with the Gulf of Guinea

-17 ° -16 ° -15 ° -14 ° -13 ° -12 °

longitude

13 °

14 °

15 °

16 °

latit

ude

D akar

S t Louis

Podor

Louga

Linguère

M atam

M bour

Kaolack

Bakel

Tam bacounda

KoldaZ iguinchor

Kédougou

Bam bey

D iourbel

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

Achievements

- Capacity building (human and infrastructure)

- linkage with other teams (AF07)

-contribution to National communication

(members of Senegal and Botswana National CC committees)

Continuing work on RCM and assessment of scenarios…..