climate modeling idania rodriguez eees phd student idania rodriguez eees phd student “science...
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Climate ModelingClimate Modeling
Idania Rodriguez
EEES PhD Student Idania Rodriguez
EEES PhD Student
“Science Explorations Through the Lens of Global Climate Change” Workshop
OutlineOutline
• Introduction• Motivation • Building a Climate Model• Model Complexity• Model Uncertainty• Model Validation
• Introduction• Motivation • Building a Climate Model• Model Complexity• Model Uncertainty• Model Validation
What is a Climate Model?What is a Climate Model? a mathematical representation of
physical, biological and chemical processes that determine climate
a mathematical representation of physical, biological and chemical processes that determine climate
• Mathematical Equationso Ordinary Differential time-dependento Partial Diff. time- & space-dependento Parameterized 1 parameter in terms of 2+o Empirical reproduce observed results
Computers are needed to solve the equations arising from climate models
• Mathematical Equationso Ordinary Differential time-dependento Partial Diff. time- & space-dependento Parameterized 1 parameter in terms of 2+o Empirical reproduce observed results
Computers are needed to solve the equations arising from climate models
MotivationMotivationHumans have affected and will likely continue to affect Earth’s climate
Climate models can• Help us understand sensitivities of
climate system• Project future changes from plausible
scenarios• Illustrate benefits of mitigating impacts
caused by these potential changes as an instrument of climate policy
Humans have affected and will likely continue to affect Earth’s climate
Climate models can• Help us understand sensitivities of
climate system• Project future changes from plausible
scenarios• Illustrate benefits of mitigating impacts
caused by these potential changes as an instrument of climate policy
Global Mean Radiative Forcing by 2005 (WmGlobal Mean Radiative Forcing by 2005 (Wm-2-2) )
Cloud Processes
Surface Processes
RadiativeProcesses
Meteorological Processes
Transport Processes
GasProcesses
AerosolProcesses
Building a Climate ModelBuilding a Climate Model
Source: Adapted from IPCC, 2001a
Model ComplexityModel ComplexityFrom the simplest model…
to an AOGCM
From the simplest model…
to an AOGCM
Source: IPCC 2001
EiE
Ein Eout
Tempave
[CO2]
Model ComplexityModel ComplexityHow do these models differ?• Space Resolution
How do these models differ?• Space Resolution
Land/Land/OceanOcean
AtmosphereAtmosphereEnergy & Energy & MassMassTransferTransfer
2-Box 2-Box No land/ocean distinctionNo land/ocean distinction
LandLand
AtmosphereAtmosphere
OceanOcean
3-Box 3-Box No vertical or horizontal distinctionNo vertical or horizontal distinction
Model ComplexityModel Complexity• Inclusion/Complexity of Processes• Input Properties• Inclusion/Complexity of Processes• Input Properties
Multi-box multi-layerMulti-box multi-layer
LandLand
AtmosphereAtmosphere
OceanOceanAOGCM AOGCM Each 3D cell - few Each 3D cell - few o o of latitude & of latitude & longitude / 10-40 layerslongitude / 10-40 layers
Model ComplexityModel Complexity• Space/Time Scale
Inputs to a climate model depend on what we want to learn from it…
• Space/Time Scale
Inputs to a climate model depend on what we want to learn from it…
Million-year global projectionMillion-year global projection
AtmosphereAtmosphere
OceansOceans
Cryosphere (sea ice/glaciers)Cryosphere (sea ice/glaciers)
Land surface & biotaLand surface & biota
Biogeochem cyclesBiogeochem cycles
Solar input long-term Solar input long-term variation variation
Regional climate over next Regional climate over next centurycentury
AtmosphereAtmosphere
OceansOceans
Day to night variationsDay to night variations
More geographic detail More geographic detail of region of region
More temporal detail of More temporal detail of regionregion
Model ComplexityModel Complexity• Sub-grid scale effects
o Partial differential eqns arising from processes cannot be solved analytically
o GCMs break the atmosphere, land and oceans on grid boxes & average processes to that scale to approximate solutions
But many events relevant to climate happen on smaller scales, e.g. clouds
Solution: treat implicitly using “parameterizations”
• Sub-grid scale effectso Partial differential eqns arising from
processes cannot be solved analyticallyo GCMs break the atmosphere, land and
oceans on grid boxes & average processes to that scale to approximate solutions
But many events relevant to climate happen on smaller scales, e.g. clouds
Solution: treat implicitly using “parameterizations”
Grid sky half-Grid sky half-covered bycovered bycloudsclouds
Grid skyGrid skyuniformly uniformly lightly lightly covered - covered - 1/2 sunlight1/2 sunlight
Model UncertaintiesModel Uncertainties• Future emissions• Future emissions
Model UncertaintiesModel Uncertainties
• Approximations/Simplifications to Chemical, Physical & Biological Processes• Example: GATOR-GCMM includes organic
chemistry using a condensed mechanism OLE + O3 CH3CHO + H2COO + XOP
vs. C2H4 + O3 HCHO + H2COO (explicit)
• Using numerical methods to solve ODEs/PDEs instead of analytical solutions
• Sub-grid scale effects / Parameterizations
• Approximations/Simplifications to Chemical, Physical & Biological Processes• Example: GATOR-GCMM includes organic
chemistry using a condensed mechanism OLE + O3 CH3CHO + H2COO + XOP
vs. C2H4 + O3 HCHO + H2COO (explicit)
• Using numerical methods to solve ODEs/PDEs instead of analytical solutions
• Sub-grid scale effects / Parameterizations
C=C
Model UncertaintiesModel Uncertainties
• Poorly understood phenomenao Cloud effects on climate (aerosol
indirect)
• Poorly understood phenomenao Cloud effects on climate (aerosol
indirect)
Model ValidationModel ValidationHow can we know the model works?Diverse Techniques• Climatic response to volcanic eruptions
How can we know the model works?Diverse Techniques• Climatic response to volcanic eruptions
Volcanoes effect on global temperature
Black: actual temperature
Yellow: 14 different models
Red: averageof all simulations
Source: AR4WG1, IPCC, 2007
Model ValidationModel Validation• Modeling past climate trends• Modeling past climate trends
Source: IPCC, 2001
Model ValidationModel ValidationOther Techniques• Modeling seasonal temperature variations• Comparing to geographical patterns
o Precipitation
• Comparing to effects of climate predictedo Animal & plant response to climate change
Other Techniques• Modeling seasonal temperature variations• Comparing to geographical patterns
o Precipitation
• Comparing to effects of climate predictedo Animal & plant response to climate change
Questions?Questions?
Thank you for your attention
Thank you for your attention