Transcript Assessing Global and Regional climate change scenarios for West

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
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.
GOALS
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
PREVIOUS WORK
- Provide requisite climate change scenarios needed to
undertake vulnerability studies
Methods
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
- MSL
- DT, DP patterns at global scale
Magicc/Scengen
Data (site climatic
observations)
Regression schemes
DT, DP at local scale
Mali Grid box for GCM at 5°x5° resolution
16°
latitude
15°
sensibilité = 1,5°C
14°
13°
12°
-17°
-16°
-15°
-14°
-13°
-12°
longitude
16°
latitude
15°
14°
sensibilité = 2,5°C
13°
12°
-17°
-16°
-15°
-14°
-13°
-12°
longitude
16°
sensibilité = 4,5°C
latitude
15°
14°
13°
12°
-17°
-16°
-15°
-14°
longitude
-13°
-12°
Which GCM to use?
Horizon 2025
15
10
Delta_P (% )
5
0
0
0,5
1
1,5
-5
2
2,5
- above normal
- normal
- below normal
-10
-15
-20
Delta_T (°C)
Scatterplot of Temperature and Precipitation projections
showing 3 categories of outpouts (2025)
PRESENT OBJECTIVES
(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
Flow shart of methods
TROPICAL TROPOSPHERIC
DYNAMICS ALREADY
DEVELOPED
GCM
(CCSM/NCAR)
DEVELOPMENT OF
A MESOSCALE MODEL
FOR TROPICAL SYSTEMS
RUNNING
A REGIONAL CLIMATE
MODEL
(MM5 v3)
A REALISTIC WESTERN AFRICA REGIONAL
CLIMATE MODEL THAT MAY ADDRESS
ISSUES LIKE:




LOCAL
EFFECTS
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
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 data
from CCSM and emission scenario (SRES A1, ….)
Evalutation of Mean State
observed
simulated
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
present
future
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)
Podor
St Louis
16 °
Matam
Louga
Linguère
latitude
15 °
Dakar
Bakel
Bambey
Mbour
Diourbel
Kaolack
14 °
Tambacounda
13 °
Ziguinchor
-17 °
-16 °
Kolda
Kédougou
-15 °
-14 °
longitude
-13 °
-12 °
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…..