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Simulating and Forecasting
Regional Climates of the Future
William J. Gutowski, Jr.
Dept. Geological & Atmospheric Sciences
Dept. of Agronomy
Iowa State University
Major contributions from:
Z. Pan, R. W. Arritt, C. Anderson, F. Otieno, E. S. Takle
Iowa State University
J. H. Christensen, O. B. Christensen
Danish Meteorological Institute
Copenhagen, Denmark
ISU Plant Pathology
(March 2001)
Outline
• Regional Climate Models (RCMs)
– Why?
– Physical Basis
– Simulation Considerations
• A Norm to Evaluate Projected Change
• Conclusions
ISU Plant Pathology
(March 2001)
Outline
• Regional Climate Models (RCMs)
– Why?
– Physical Basis
– Simulation Considerations
• A Norm to Evaluate Projected Change
• Conclusions
ISU Plant Pathology
(March 2001)
Why Regional Climate Models?
Global Climate Models:
• nearly closed system
• complete representation
Why Regional Climate Models?
Global Climate Models:
• nearly closed system
• complete representation
However:
• high computing demands
• limits resolution
• many surface features unresolved (esp. human-scale)
Why Regional Climate Models?
Regional Climate Models:
• sacrifice global coverage
• higher resolution
TERRAIN HEIGHT
Global
Model
Resolution
DX = 250 km
contours
every
250 m
TERRAIN HEIGHT
Regional
Model
Resolution
DX = 50 km
contours
every
250 m
TERRAIN HEIGHT
Future
Model
Resolution?
DX = 10 km
contours
every
250 m
Outline
• Regional Climate Models (RCMs)
– Why?
– Physical Basis
– Simulation Considerations
• A Norm to Evaluate Projected Change
• Conclusions
ISU Plant Pathology
(March 2001)
RCM Foundation:
Conservation Laws of Physics
1. Conservation of Thermodynamic Energy
(First Law of Thermodynamics)
2. Conservation of Momentum
(Newton’s Second Law)
3. Conservation of Mass
Conservation
of “M”
DM
?
Dt
Conservation
of “M”
Source/sink 0
DM
0
Dt
Conservation
of “M”
DM
0
Dt
Conservation
of “M”
DM
0
Dt
Conservation
of “M”
Source/sink 0
DM
0
Dt
RCM Foundation:
Conservation Laws of Physics
1. Conservation of Thermodynamic Energy
(First Law of Thermodynamics):
Heat input = D (internal energy) + (work done)
Transport and accumulation
by circulation
Radiation to/from space
Heat
Source/Sink
Condensation
“Contact” heat exchange
Radiation to/from surface
RCM Foundation:
Conservation Laws of Physics
2. Conservation of Momentum
(Newton’s Second Law):
D(wind)/ D(time) = S(forces)
RCM Foundation:
Conservation Laws of Physics
3. Conservation of Mass:
Special constituent - water
Moisture
In/Out
D(Moist ure
0
Dt
Evapotranspiration
Precipitation
Water Cycle
Q
Q
P
E
P
E
R
Water Cycle
Heat released
E
Heat absorbed
Water is thus a primary
form of heat transport
heat absorbed when evaporates
released when water condenses
largest individual source of energy
for the atmosphere
Water Cycle
Radiation absorbed by water & re-emitted
Water is thus a primary
form of heat transport
heat absorbed when evaporates
released when water condenses
largest individual source of energy
for the atmosphere
and greenhouse gas
~ transparent to solar
absorbs/emits infrared
RCM Foundation:
Fundamental Laws of Physics
1. Conservation of Thermodynamic Energy
(First Law of Thermodynamics)
2. Conservation of Momentum
(Newton’s Second Law)
3. Conservation of Mass
Plus: Ideal Gas Law
Outline
• Regional Climate Models (RCMs)
– Why?
– Physical Basis
– Simulation Considerations
• A Norm to Evaluate Projected Change
• Conclusions
ISU Plant Pathology
(March 2001)
Evapotranspiration
Evapotranspiration
E ~ - CW{eair-esat(Ts)}
Evapotranspiration
E ~ - CW{eair-esat(Ts)}
CW = CW(atmos.)
but also
CW = CW(physiology)
soil moisture
CW
leaf temp.
sunlight
CO2 level
RCM Horizontal Grid
(IMAX,JMAX)
I
(1,1)
J
RCM Horizontal Grid
(IMAX,JMAX)
I
(1,1)
J
RCM Horizontal Grid
How does a
“flat” grid ...
RCM Horizontal Grid
?
How does a
“flat” grid ...
...represent part of
the spherical earth?
RCM Horizontal Grid
By projection
to a flat plane
RCM Horizontal Grid
True at 90o
Polar
Stereographic
RCM Horizontal Grid
True at, e.g.,
30o and 60o
Lambert
Conformal
RCM Horizontal Grid
Mercator
True
at 0o
RCM Horizontal Grid
Forcing Frame:
for lateral
boundary conditions
“free” interior
Earth Climate System
Q
P
E
E
R
Scales of Climate
Global
Regional
Microscale
Regional
Microscale
Microscale
Regional
Microscale
Regional
Microscale
Microscale
Microscale
Microclimate C
Solar, IR, wind,
CO2, CO, NOx,SO2,
H2O, temperature,
trace gases, shading,
particulate matter
Solar, IR, wind,
CO2, CO, NOx,SO2,
H2O, temperature,
Solar, IR, wind,
CO2, CO, NOx,SO2,
H2O, temperature,
Chemicals
Erosion
Management
Soil Pathogen D
Human
Influences
Plant B
Chemicals
Crop B
Soil Pathogen B
Plant A
Particulate Deposition, Precipitation, Solar Radiation, IR
Crop A
Management
Microscale
trace gases, shading,
particulate matter
Microclimate B
trace gases, shading,
particulate matter
Microclimate A
Microscale
Soil A
Soil A
Soil C
Soil B
Soil B
H2O, temperature,
nutrients, microbes,
soil carbon, trace chemicals
H2O, temperature,
nutrients, microbes,
soil carbon, trace chemicals
H2O, temperature,
nutrients, microbes,
soil carbon, trace chemicals
H2O, temperature,
nutrients, microbes,
soil carbon, trace chemicals
H2O, temperature,
nutrients, microbes,
soil carbon, trace chemicals
Hydrology, Soil Microbiology, Soil Biochemistry
Field
Field
Field
Regional
Field
Field
Field
Regional
Field
Regional
Continental
Scales of Landforms
Field
Field
Regional
Field
Outline
• Regional Climate Models (RCMs)
– Why?
– Physical Basis
– Simulation Considerations
• A Norm to Evaluate Projected Change
• Conclusions
ISU Plant Pathology
(March 2001)
Projections of Future Climate
Simulate decades/centuries into future
How are projections verified?
Projections of Future Climate
Simulate decades/centuries into future
How are projections verified?
• Accuracy of present climate simulation?
Projections of Future Climate
Simulate decades/centuries into future
How are projections verified?
• Accuracy of present climate simulation?
• Accuracy of paleoclimate simulation?
Projections of Future Climate
Simulate decades/centuries into future
How are projections verified?
• Accuracy of present climate simulation?
• Accuracy of paleoclimate simulation?
• Alternative …
Projections of Future Climate
Simulate decades/centuries into future
How are projections verified?
• Accuracy of present climate simulation?
• Accuracy of paleoclimate simulation?
• Alternative …
Cross-Compare Multiple Simulations
Model
Observed
RegCM2
NCEP
Hadley
Reanalysis Centre
(1979-1988) (~1990’s)
HIRHAM
(DMI)
“
GCM-control GCMScenario
“
Hadley
Centre
(2040-2050)
“
Simulation Domain
Possible Comparisons?
Reanalysis
HadCM
Cont/Scen
Driving
RegCM2
OBS
HIRHAM
HadCM
Cont/Scen
Differences
Definition of Biases
Reanalysis
RegCM2
OBS
RCM (performance) bias
Definition of Biases
Reanalysis
RegCM2
Inter-model
bias
HIRHAM
Definition of Biases
Reanalysis
RegCM2
Forcing
bias
HadCM
RegCM2
Definition of Biases
RegCM2
HadCM
G-R
nesting
bias
HadCM
Climate Change
HadCM
control
RegCM2
Change
HadCM
scenario
RegCM2
Climate Change
P
Change
Control
Scenario
Climate Change
P
Max Bias
Control
Change
Scenario
Analysis Regions
SE
0
1
2
0
1
2
0
1
2
Annual Snow Cycle
ReGCM2 Sierra
HIRHAM Sierra
500
400
NCEP
HCONT
HSCEN
Snow Depth [mm H 2O]
Snow Depth [mm H 2O]
500
300
200
100
0
AUG
400
NCEP
HCONT
HSCEN
300
200
100
OCT
DEC
FEB
Month
APR
JUN
0
AUG
OCT
DEC
FEB
Month
APR
JUN
Outline
• Regional Climate Models (RCMs)
– Why?
– Physical Basis
– Simulation Considerations
• A Norm to Evaluate Projected Change
• Conclusions
ISU Plant Pathology
(March 2001)
FIELD
POSSIBLE
CHANGE
CONFIDENCE **
Precipitation
+ 3-5 mm/d
(North)
good
+ 0-1 mm/d
(South)
fair
+ 2 Ğ 3 oC
fair
- 0-50%
poor
Tmin, Tmax
Snow
** = Subject to quality of driving GCM!
ISU Plant Pathology
(March 2001)
Conclusions
• Ratio of climate change to biases is
especially large in the California region
• Differences between RCM and GCM
imply room for RCMs to add value to
GCM simulations
• Regional warming signal is less robust
than precipitation change
• Future warming projection has large
inter-model differences
ISU Plant Pathology
(March 2001)
Acknowledgments
Primary Funding:
Electric Power Research Institute
(EPRI)
Additional Support:
U.S. National Oceanic and Atmospheric
Administration
U.S. National Science Foundation
ISU Plant Pathology
(March 2001)
EXTRA
SLIDES
Precip [mm/day]
Analysis
Points
1
2
3
4
5
October - March (RegCM2)
20
[mm/d]
15
10
5
0
OBS-1
NC-1
HCont-1 HScen-1
October - M arch (RegCM2)
20
[mm/d]
10
5
10
10
5
OBS-1
NC-1
HCont-1 HScen-1
20
0
5
OBS-2
NC-2
0
HCont-2 HScen-2
October - M arch (RegCM2)
20
15
OBS-3
NC-3
October - M arch (RegCM2)
15
10
5
0
October - M arch (RegCM2)
15
[mm/d]
0
20
15
[mm/d]
[mm/d]
15
October - M arch (RegCM2)
[mm/d]
20
10
5
OBS-4
NC-4
HCont-4 HScen-4
0
OBS-5
NC-5
HCont-5 HScen-5
HCont-3 HScen-3
April-Septem ber (RegCM2)
8
[mm/d]
6
4
2
0
OBS-2
NC-2
HCont-2 HScen-2
April-September (RegCM2)
April-September (RegCM2)
8
6
6
6
4
2
4
2
OBS-1
NC-1
HCont-1 HScen-1
0
OBS-2
NC-2
8
6
6
2
OBS-3
NC-3
April-September (RegCM2)
8
4
0
HCont-2 HScen-2
April-September (RegCM2)
0
4
2
[mm/d]
0
[mm/d]
8
[mm/d]
8
[mm/d]
[mm/d]
April-September (RegCM2)
4
2
OBS-4
NC-4
HCont-4 HScen-4
0
OBS-5
NC-5
HCont-5 HScen-5
HCont-3 HScen-3
Precipitation Regions
Upper
Miss.
Range: 600 - 970 mm
Range: 650 - 850 mm
Range: 590 - 870 mm
Energy Balance for Earth
Energy Balance for Earth
Planetary
Albedo
Energy Balance for Earth
Energy Balance for Earth
Conservation of Momentum
~ Newton’s Second Law ~
Forces/mass:
gravity
pressure gradient
friction
Conservation of Momentum
~ Newton’s Second Law ~
Rotating Frame
X
R
Conservation of Momentum
~ Newton’s Second Law ~
Rotating Frame
dV3
(Forces/ m ass)
dt
2
2 V3 R
Conservation of Momentum
~ Newton’s Second Law ~
Sphere, Rotating Frame
du uv tan uw
1 p
2v sin 2wcos Frx
dt
a
a
x
dv u 2 t an vw
1 p
2usin
dt
a
a
y
dw u2 v 2
dt
a
rotation of direction
Fry
1 p
2u cos g Frz
z