Global Hydrology Modelling: Running Multiple Ensembles with the 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)

OutlineThe hydrological model & project backgroundProjected changes in global annual runoffProjected changes in seasonal runoffProjected changes in global water resources stresses

Description of the Hydrological & Project Background

The hydrological model: Mac-PDMMac-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):RainfallTemperature HumidityWindspeedCloud cover

The NERC QUEST-GSI projectAim 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:+0.5C+1.0 C+1.5 C+2.0 C+2.5 C+3.0 C+4.0 C+5.0 C+6.0 C

The NERC QUEST-GSI projectThe 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 grid6.05.04.03.02.52.01.51.00.5xxxxxxxxxxxxxxxxxxxxxxxxxxxUKMO HadGEM1xxxxxxxxMRI CGCM232AxxxxxxxxINM CM30xxxxxxxxIAP FGOALS10GxxxxxxxxGISS MODELERxxxxxxxxGISS MODELEHxxxxxxxxGISS AOMxxxxxxxxGFDL CM21xxxxxxxxCSIRO MK5xxxxxxxxCNRM CM3xxxxxxxxCCSR MIROC32MEDxxxxxxxxCCSR MIROC32HIxxxxxxxxCCCMA CGCM31T63xxxxxxxxBCCR BCM20xxxxxxxxNCAR CCSM30xxxxxxxxMPI ECHAM5xxxxxxxxIPSL CM4xxxxxxxxCCCMA CGCM31xxxxxxxxUKMO HadCM3Prescribed TemperatureGCM used to provide climate dataRunning on Linux Desktop:1 run = 3 hours9 runs = 27 hours171 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 changes9 model runs 18 model runs 81 model runs Sign of change varies by GCM

The challenge of summarising the resultsBut there are issues with the ensemble meanThe ensemble mean

The challenge of summarising the resultsNumber of models in agreement

Projected Changes in the Seasonal Cycle of Average Runoff

Mekong Basin&Liard Basin

The Mekong

The MekongChanges in sign vary by GCM.

Magnitude of changes increase with temperature

The Liard

The Liard

Projected Changes in Global Water Stress

Calculating stressesA 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 scenariosSRES A1BSRES A2SRES B2

Stresses calculated for the 2050s with different prescribed warming (0.5-6.0C)

Global water resources stressesHadCM3

HadCM3IPSL CM4CCSR MIROC32HIGlobal water resources stresses

HadCM3IPSL CM4CCSR MIROC32HIGlobal 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 stressesLittle uncertainty due to population change but much due to GCM choice

Summary and ConclusionsUse of the campus grid has reduced run time from 21 days to 9 hoursThis allows a comprehensive investigation of climate change impacts uncertaintyResults demonstrate:GCM structure is a major source of uncertaintySign and magnitude of runoff changes varies across GCMsFor water resources stresses, population change uncertainty is relatively minor

Thank you for your timeVisit www.walker-institute.ac.uk