virtual experiment © oregon state university models as a communication tool for hja scientists...
TRANSCRIPT
Virtual Experiment
© Oregon State University
Models as a communication tool for HJA scientists
Kellie Vache and Jeff McDonnell
Dept of Forest Engineering
HJA Science Hour
Virtual Experiment
© Oregon State University
Outline
A rationale for modeling in LTER 5
The STELLA concept
Going beyond STELLA (visualization, more complex models, other languages, etc
Conclusions
Virtual Experiment
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A rationale for modeling
in LTER 5
Virtual Experiment
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LTER 5
How do land use, natural disturbances, and climate change affect three key sets of ecosystem services: carbon and nutrient dynamics, biodiversity, and hydrology?
our component areas: (1) climate, (2) hydrology, (3) disturbance, (4) ecophysiology, (5) carbon and nutrient dynamics, (6) biodiversity, and (7) stream-forest interactions.
A major goal will be to test predictive rules (i.e., hypotheses) regulating temporal behaviors.
Virtual Experiment
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LTER 20-yr review 2002
Recommendation 4. Ecological research by LTER scientists involving multiple disciplines, dimensions and scales should be organized a priori by hypotheses and theory, and tested by predictive models across broader and broader phenomena.
Virtual Experiment
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Why should we consider models?
We have a stated desire and need to integrate across the bio-geo-hydro interface
Our group discussions are often left rather open ended
We tend to get caught up in the details of our particular field or area of interest
We have difficulty with each other’s jargon and terminology
Virtual Experiment
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Another issue
We may all visit and look at thesame spot on the landscape, but may view it very differently based on our disciplinary focus
Virtual Experiment
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Sapflow! DOC, DOC, DON!DON!
StreamRouting!
Soil depth!
Lateral flow!!!
Our dominant processes bias
Virtual Experiment
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Sapflow
DOC flushing
Lateral flow
Soil depth
Stream routing
Watershed Function
Virtual Experiment
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Sapflow
DOC flushing
Lateral flow
Soil depth
Stream routing
Watershed Function
Virtual Experiment
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Representing content
in biogeochem
Representing content
in geomorph
Representing contentin hydrology
Representing contentin plant phys
General HJA system
representation
BiogeochemContent Represented
GeomporhContent
Represented
Plant Content Represented
Plant Content Represented
Virtual Experiment
© Oregon State University
A STELLA PRIMER
Virtual Experiment
© Oregon State University
What is STELLA?
A visual modeling environment Simulations developed through ‘dragging and dropping’ of a
standard set of modeling components
OR
A software tool designed to simulate dynamic systems.
OR
A tool to develop and solve systems of ordinary differential equations
Virtual Experiment
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Density independent population growth Described mathematically as a differential equation:
Can be solved for population through integration:
A STELLA Example
rNdt
dN
Where N = population size and r = birth rate
rtt eNN 0 Where N0 = initial population size
and Nt = population at any time t
0250005000075000
100000
0 10 20 30 40
Time
Po
pu
lati
on
Plugging into a spreadsheet
Virtual Experiment
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RUN STELLA HERE
Virtual Experiment
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A STELLA Rainfall/Runoff Model
So il
Discharge
Degree of Saturation
kS low
Po ro sity
Depth To B edrock
~
Rain
Rain Rate
Virtual Experiment
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STELLA discussions thusfar
ET1~
throughfall
m1
K1
soil1
Ks1
soil2
soilmoisture1
soilmoisture2
K2
m2
Ks2
soil3
flux
C3
C4
flux4
soilmoisture3
DOC1
DOC4
flux2
DOC conc2
DOC2
flux3
DOC3
C2
Ks3
Ohorizon
sorption2
sorption1
C1
sorption3
K3
m3 soil4
soilmoisture4m4
Ks4
K4
sorption4
DOC conc3
DOC conc4
ET2
ET3
ET4
PET2
PET1
PET3
PET4
~PET
flux5
DOC1 conc1
Virtual Experiment
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Some initial results
Dirt plot simulations
0
20
40
60
80
100
120
140
2/9/99 5/20/99 8/28/99 12/6/99 3/15/00 6/23/00 10/1/00 1/9/01 4/19/01
A_measured DOC 10 cm
predicted DOC 0-10 cm
B_measured DOC 10 cm
C_measured DOC 10 cm
D_measured DOC 10 cm
E_measured DOC 10 cm
Virtual Experiment
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Going beyond STELLA
Virtual Experiment
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Limitations of the STELLA Approach
As a model becomes more complex, the STELLA environment becomes quite clunky
Spatial distribution of boxes is difficult
Direct incorporation of GIS data not feasible
Limited output potential
Virtual Experiment
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Grid-based hydrologic models (eg. DHSVM) move water laterally and vertically, but each grid cell is, in fact, cast as a 1 dimensional lumped model
A complicated STELLA-like simulation
Lettenmaier, 2002
Beyond STELLA – A brief example
Individual STELLA–like boxes!
Important processes could be explored as a STELLA model
Subsequent allocation and solution of many boxes, potentially using a GIS based grid, might then occur in a more fully featured language
Virtual Experiment
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A distributed model that began with STELLA explorations
•Data originated as 50 m gridded DEM
•Simple assumptions about soil depth, porosity, rainfall distribution, etc.
•DHSVM like routing structure
•Simple models of ET, drainage, etc.
•Map color represents depth to water table
Virtual Experiment
© Oregon State University
A distributed model that began with STELLA explorations
•Data originated as 50 m gridded DEM
•Simple assumptions about soil depth, porosity, rainfall distribution, etc.
•DHSVM like routing structure
•Simple models of ET, drainage, etc.
•Map color represents depth to water table
Virtual Experiment
© Oregon State University
Conclusions
Virtual Experiment
© Oregon State University
Conclusions
While we will likely each continue to use detailed, process-specific models, a “group model” could be something we consider within LTER 5
We all take ownership in its development and construction
We use it to identify and explore disciplinary interfaces
A modeler could then incorporate this ‘simple’ model into a more sophisticated modeling environment
Virtual Experiment
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Hypotheses that might be tested with a model
McDonnell Group Focus: What are potential effects of rainfall distribution on the accumulation
and movement of water in the system? How might spatially variable depth to bedrock effect water
movement? Can the model simulate residence time? How does it compare to
Kevin McGuire’s measurement based estimates? What does this say about the model?
How does the model split old water vs. new water?
HJA Group Focus: What are the potential effects of stand age or species change on
hydrologic response? How do paired catchment studies reflect the larger lookout creek
basin? How might geomorphology interact with hydrology? What are the potential meso-scale effects of wildfire?
Virtual Experiment
© Oregon State University