global hydrology modelling: running multiple ensembles with the campus grid simon gosling walker...
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Global Hydrology Modelling: Global Hydrology Modelling: Running Multiple Ensembles with Running Multiple Ensembles with
the Campus Gridthe Campus Grid
Simon GoslingWalker Institute for Climate System Research,
University of Reading
Thanks to Dan Bretherton (Reading e-Science Centre)
and Nigel Arnell (Walker Institute)
Outline
• The hydrological model & project background• Projected changes in global annual runoff• Projected changes in seasonal runoff• Projected changes in global water resources stresses
Description of the Hydrological & Project Background
The hydrological model: Mac-PDM
• Mac-PDM is written in Fortran and simulates river flows across the globe on a 0.5x0.5 degree grid.
• Input data from global climate models (GCMs):– Rainfall– Temperature – Humidity– Windspeed– Cloud cover
The NERC QUEST-GSI project
• Aim is to examine the global scale impacts of climate change on the hydrological cycle and water resources.
• If global temperature was to rise by a certain amount, what would the impacts be?- Investigate impacts for the following 9 prescribed mean global
temperature changes relative to present:- +0.5ºC
- +1.0 ºC
- +1.5 ºC
- +2.0 ºC
- +2.5 ºC
- +3.0 ºC
- +4.0 ºC
- +5.0 ºC
- +6.0 ºC
The NERC QUEST-GSI project
• The climate data is taken from an ensemble of GCMs to explore the role of climate model structural uncertainty.
Source: Collins et al. (2006) Towards quantifying uncertainty in transient climate change. Climate Dynamics 27: 127-147
Running on the campus grid
6.05.04.03.02.52.01.51.00.5
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xxxxxxxxUKMO HadGEM1
xxxxxxxxMRI CGCM232A
xxxxxxxxINM CM30
xxxxxxxxIAP FGOALS10G
xxxxxxxxGISS MODELER
xxxxxxxxGISS MODELEH
xxxxxxxxGISS AOM
xxxxxxxxGFDL CM21
xxxxxxxxCSIRO MK5
xxxxxxxxCNRM CM3
xxxxxxxxCCSR MIROC32MED
xxxxxxxxCCSR MIROC32HI
xxxxxxxxCCCMA CGCM31T63
xxxxxxxxBCCR BCM20
xxxxxxxxNCAR CCSM30
xxxxxxxxMPI ECHAM5
xxxxxxxxIPSL CM4
xxxxxxxxCCCMA CGCM31
xxxxxxxxUKMO HadCM3
Prescribed Temperature
GC
M u
sed t
o p
rovid
e c
limate
data
Running on Linux Desktop:
1 run = 3 hours
9 runs = 27 hours
171 runs = 513 hours (21 days)
On the campus grid:
171 runs = 9 hours
Projected Changes in Global Average Annual Runoff
Multiple ensembles for various prescribed temperature changes
9 model runs 18 model runs 81 model runs
Sign of change varies by GCM
The challenge of summarising the results
But there are issues with the ensemble mean
The ensemble mean
The challenge of summarising the results
Number of models in agreement
Projected Changes in the Seasonal Cycle of Average Runoff
Mekong Basin&
Liard Basin
The Mekong
The Mekong
Changes in sign vary by GCM.
Magnitude of changes increase with temperature
The Liard
The Liard
Projected Changes in Global Water Stress
Calculating stresses
• A region is stressed if water availability is less than 1000m3/capita/year
• Therefore stress will vary acording to population growth:– Stress calculated for 3 populations scenarios
• SRES A1B• SRES A2• SRES B2
• Stresses calculated for the 2050s with different prescribed warming (0.5-6.0ºC)
Global water resources stresses
HadCM3
HadCM3
IPSL CM4
CCSR MIROC32HI
Global water resources stresses
HadCM3
IPSL CM4
CCSR MIROC32HI
Global water resources stresses
Global water resources stresses
Global water resources stresses
Global water resources stresses
Global water resources stresses
Global water resources stresses
Global water resources stresses
Little uncertainty due to population change but much due to GCM choice
Summary and Conclusions
• Use of the campus grid has reduced run time from 21 days to 9 hours
• This allows a comprehensive investigation of climate change impacts uncertainty
• Results demonstrate:– GCM structure is a major source of uncertainty– Sign and magnitude of runoff changes varies
across GCMs– For water resources stresses, population
change uncertainty is relatively minor
Thank you for your time
Visit www.walker-institute.ac.uk