Transcript PPT, 1 MB - START - SysTem for Analysis Research and Training

Simulation of present-day climate of
tropical Africa Using the Hadley Centre
regional climate modeling system
AIACC AF 20 Project
Andre F. KAMGA , Gregory. S. Jenkins ,
Amadou T. Gaye , Adamou Garba , A.
Sarr, and A. Adedoyin
African tropics experiences a
highly variable climate and
presents a significant
vulnerability to probable
climate change.
Acquiring knowledge of possible
future climate change for the next
decades will facilitate design and
implementation of adaptation
strategies.
• Numerical simulations with Global Circulation
Models (GCMs) are appropriate tools to
address global to sub-continental scale climate
change and impacts ( Giorgi et al. 2002)
• To address country, sub-country and local scale
climate change consequences or impacts, high
resolution climate Scenarios are required.
Regional Climate Models (RCM) are tools to
develop high resolution climate scenarios.
• We examine hereunder a RCM simulation of
some aspects of present-day (61-90) climate of
tropical Africa.
Why do we examine models
simulations?
• To guide future improvements of
climate models
• To facilitate interpretation and use of
models climate forecasts or climate
change scenarios.
Precis is a regional climate modeling system
developed by UK Metoffice Hadley Centre
for climate prediction and research.
The Hadley center regional climate
modeling system have been used to conduct
experiments over Europe, India and
Southern Africa.
The Boundary Conditions Are Provided by a
30 Year ( 1961-1990) Integration of
HADAM3H Which Is an Atmospheric
Higher Resolution (150 Km) Version of
HADCM3.
PRECIS TEMPERATURE
SIMULATIONS AND NCEP/CDAS
REANALYSIS.
Temperature Climatology
• Temperatures above 30°C at sub-country scale are
simulated with positive Biases up to 2°C.
• Regional monthly variability of temperature is
well captured by Precis.
• Locations with high temperatures ( > 30°C) are
well simulated by PRECIS RCM.
• Therefore, there may be some skill in capturing
areas at a sub-country scale that may
experience temperatures above a given
threshold in future climate scenarios with
Precis.
PRECIS PRECIP
SIMULATIONS AND CRU
ANALYSIS.
• Precipitation is overestimated over the ITCZ .
• Regional annual cycle of precipitation is well
captured.
• Heavy precipitation locations in the ITCZ core are
simulated.
• Therefore, there may be some skill in capturing areas
that may experience heavy precipitation or flooding
with overestimation of precipitation intensity.
Discussions
• There is generally a surface temperature
warm bias (1-2°C) over much of land
areas. A systematic strengthening of St
Helena High as well as the low-level
monsoon winds (warm air masses) are
common behavior of many GCMs.
Therefore, the warm bias in the RCM is
probably related to circulation bias of the
driving GCM.
• Moreover, a tropospheric cold bias in the
tropics has been noted in the driving
GCM leading to a reduction of static
stability, promotion of convective ascent,
and intensification of the hydrological
cycle.
• The observed overestimation of
precipitation in the RCM over ITCZ is
probably related to biases in the
circulation and temperature profiles of
the driving GCM.
CONCLUSION
« The annual cycle of precipitation and
temperature are well simulated by the RCM
from sub-continental to sub-country scales.
Sub-continental to sub-country scale areas
that have experienced heavy precipitation
and high temperatures are reasonably well
captured. »
RCM runs with Reanalysis as driving data
may shed some lights on the extent to which
the main source of RCM biases are the
driving GCM data.
To improve our capacity to interpret and
use models, extensive validation
experiments are needed and relationships
between scenarios verification and
scenarios value could be investigated.
“ If forecasts or a climate change scenarios do
not contain the information one needs, or are
not presented in a manner such that one can
extract that information then one simply stops
buying them and speaks badly of them in cities
wine bars or sue the forecasts vendors.”