Design of Experiment and Assessing Interactions within Atmospheric Processes Dev Niyogi North...
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- Design of Experiment and Assessing Interactions within
Atmospheric Processes Dev Niyogi North Carolina State University
Email: dev_niyogi@ncsu.edu
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- Human thinking is logical, sequential, and linear Real world is
Convulated, Non-linear, and Interactive
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- Some References Some References Mesoscale Meteorological
Modeling, Roger Pielke Sr., Second Edition.
(blue.atmos.colostate.edu)Mesoscale Meteorological Modeling, Roger
Pielke Sr., Second Edition. (blue.atmos.colostate.edu) Box, Hunter
and Hunter, Design of Experiment, 1987Box, Hunter and Hunter,
Design of Experiment, 1987 Stein and Alpert, Factor Separation
Analysis, J. Atmos. Sci. 1993Stein and Alpert, Factor Separation
Analysis, J. Atmos. Sci. 1993 Alpert et al., How good are
sensitivity studies?, J. Atmos. Sci. 1995Alpert et al., How good
are sensitivity studies?, J. Atmos. Sci. 1995 Henderson- Sellers, A
fractional factorial approach, J. Climate, 1993Henderson- Sellers,
A fractional factorial approach, J. Climate, 1993 Niyogi et al.
1995, Env. Mod. Assess, Statistical Dynamical ExperimentsNiyogi et
al. 1995, Env. Mod. Assess, Statistical Dynamical Experiments
Niyogi et al. 1999 Uncertainty in initial specification- hierarchy;
Boun. Layer Meteorol.Niyogi et al. 1999 Uncertainty in initial
specification- hierarchy; Boun. Layer Meteorol. Niyogi et al. 2002
Land surface response- midlatitudes and tropics, J. HydrometNiyogi
et al. 2002 Land surface response- midlatitudes and tropics, J.
Hydromet(www4.ncsu.edu/~dsniyogi)
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- Sensitivity Analysis Sensitivity Analysis
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- Inherent component of model studiesInherent component of model
studies Both observational as well as numerical modeling studies
rely on sensitivity analysisBoth observational as well as numerical
modeling studies rely on sensitivity analysis Approach Change a
variable see the effect on the outcomeApproach Change a variable
see the effect on the outcome
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- Sensitivity Analysis Sensitivity Analysis ObjectiveObjective
Understand the cause effect relationship Understand the relative
importance of the different processes affecting the outcome Develop
focused efforts on improving input for critical variables (GIGO)
Develop if then scenarios for policy makers; socioeconomic
analyses, Evaluate models
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- OAT Analysis OAT Analysis Inherent component of model
studiesInherent component of model studies Both observational as
well as numerical modeling studies rely on sensitivity analysisBoth
observational as well as numerical modeling studies rely on
sensitivity analysis Approach Change a variable see the effect on
the outcomeApproach Change a variable see the effect on the
outcome
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- One at A Time Analysis One at A Time Analysis
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- Another Example OAT Analysis Another Example OAT Analysis
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- Summary of OAT Analysis - Linear results -Interactions need to
be extracted in a ad- hoc manner / subjectively -Results state what
is happening and not how it is happening in the analysis
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- Sensitivity Analysis using Observations
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- -Needs careful planning (several known and unknown feedbacks
possible) -Effects cannot be switched off reliably (unlike in a
model) -Modeling OAT sensitivities could be used for developing
trends and extrapolations -Observational OAT can be largely used
for hypothesis tests (too many factors; too much noise) -KISS (Keep
it Simple Stupid) syndrome can be boon and a bane (too much
confounding and original results may be lost)
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- Sensitivity Analysis using Observations -Either Absent /
Present scenarios tested -Cloud cover and no clouds; -Irrigation
and no irrigation -Fertilizer and no fertilizer -Or High / Low
scenarios tested -High soil moisture and low soil moisture -Ambient
CO2 and Doubled CO2
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- High soil moisture Low Soil Moisture LESS DIFFUSE Measure the
environment below the two experimental domains and evaluate the
outcome (temperature, crop yield, photosynthesis, )
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- Ambient versus doubled CO2 levels
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- Example of a field sensitivity study Field Measurements at NCSU
to assess diffuse radiation feedback Does increase in diffuse
radiation fraction help crop yield?
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- MORE DIFFUSE LESS DIFFUSE Measure the environment below the two
experimental domains and evaluate the outcome (temperature, crop
yield, photosynthesis, )
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- Comparison of OAT in models and in field Comparison of OAT in
models and in field Models High Diffuse - > more
photosynthesisModels High Diffuse - > more photosynthesis
Observations High diffuse -> less temperatures -> more shade
on crops -> leaf geometry changes -> large
fluctuationsObservations High diffuse -> less temperatures ->
more shade on crops -> leaf geometry changes -> large
fluctuations
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- Clustering and Cleaning eventually gets the right results from
observations ;always an element of uncertainty that results could
have gone other way too in some scenarios. Q: Should the
observations be relied on for testing models? (of course yes; but
dont use observations as the truth!)
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- Diffuse radiation effect under cloudy conditions Diffuse
radiation effect under non- cloudy conditions
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- Clustering and Synthesis of Sensitivity Experimentation Data
Interpretation Low LAI case High LAI case Observations and Models
need to go hand in hand to help develop the understand (dont treat
observations alone as the truth)
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- Too many model evaluation studies; particularly for
synthesizing processes rely overtly on observations; Observations
are essential for model testing and evaluation But observations are
also chaotic QUESTION OBSERVATIONS Know the uncertainty associated
with the measurements Models need not agree with all observations
to be good Models give time dependent ensemble output; observations
at a given time are just that- observation at that point and/or
time Even observations have feedbacks embedded which have not been
traditionally extracted
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- No I am not a modeler! Models do not represent the reality but
neither do observations unless they are clearly synthesized. Need
to synthesize results (observations and model output) in a
nonlinear / feedback and interaction perspective
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- Modeling Analysis
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- Feedbacks and Interactions Feedbacks and Interactions
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- Feedback processes are a result of cause and effect.Feedback
processes are a result of cause and effect. That is, one follows
the other in a time sequential mannerThat is, one follows the other
in a time sequential manner The processes could be coupled as well
as uncoupledThe processes could be coupled as well as uncoupled A
-> B -> CA -> B -> C A-> B -> C ->a -> b
-> c A-> B -> C ->a -> b -> c
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- Feedbacks and Interactions Feedbacks and Interactions
Interactions, on the other hand, implies concurrence.Interactions,
on the other hand, implies concurrence. There is no cause and
effect associated with the interactions and a simultaneous effect
is associated.There is no cause and effect associated with the
interactions and a simultaneous effect is associated. A -> B
-> C and D
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- Interactions ExamplesExamples Medicine and Prescription Drug
Use Drug A will lead to helping relieve headacheDrug A will lead to
helping relieve headache Drug A taken while taking Drug B will
cause nauseaDrug A taken while taking Drug B will cause nausea Drug
A taken with coffee can cause marked improvementDrug A taken with
coffee can cause marked improvement Nutrition and Health Results
show wine is good for health; add to your diet; red wine is better;
true for people exercising Same effect as grape juice Wine is not
necessary, take out of your diet All are examples of real-life
interactions occurring which need to be resolved
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- Feedbacks and Interactions Surface Energy Balance &
EvapotranspirationSurface Energy Balance & Evapotranspiration
Rn = Etr + Shf + storage; Etr = Eg+TrRn = Etr + Shf + storage; Etr
= Eg+Tr Gradients in Surface FluxesGradients in Surface Fluxes
Non-classical CirculationNon-classical Circulation Convection and
Cumulus FormationConvection and Cumulus Formation Precipitation and
Land Use ChangePrecipitation and Land Use Change Regional Climate
ChangeRegional Climate Change
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- Factor Separation (FacSep) Analysis (Stein and Alpert, 1993;
Alpert et al. 1995; J. Atmos. Sci.) Interaction Explicit Analysis
of effect of simultaneous soil moisture and CO2 changes on
terrestrial feedback Eo = Fo = f [ CO2 -, Moist -] F1 = f [ CO2 +,
Moist - ] F2 = f [CO2 -, Moist + ] F12 = f [ CO2 +, Moist + ]
E(CO2) = F1 - Eo E(SM) = F2 - Eo E(CO2:SM) = F12 - (F1+F2) -
Fo
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- FacSep results can be interpreted and analyzed using either
time series tools or other traditional descriptive statistics
routinely used in One at A Time Sensitivity Analysis
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- Feedbacks and Interactions Feedbacks and Interactions Full
Factorial (2^n) I.e. 8 combns for 3 factors; 16 for 4; 32 for 5
etc.Full Factorial (2^n) I.e. 8 combns for 3 factors; 16 for 4; 32
for 5 etc. At three settings (low, medium, and high) this will be
3^n I.e. 27 for 3 factors, 64 for 4 factors etc.At three settings
(low, medium, and high) this will be 3^n I.e. 27 for 3 factors, 64
for 4 factors etc. Solution?Solution? Fractional Factorial Approach
(statistical design) Some confounding (all interactions /
combinations not resolved) Several design matrices routinely
available (statistics texts, software packages, internet, )
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- Fractional Factorial Designs Fractional Factorial Designs
Resolution 5 all main effects and two-factor interactions resolved
(FF0516)Resolution 5 all main effects and two-factor interactions
resolved (FF0516) Resolution 4 some two factor Xns retained
(FF0616)Resolution 4 some two factor Xns retained (FF0616)
Resolution 3 Screening type; interactions may not be resolved
(FF0508)Resolution 3 Screening type; interactions may not be
resolved (FF0508) Nonlinear response surface (fc0318)Nonlinear
response surface (fc0318) Effect = Main Effect + InteractionEffect
= Main Effect + Interaction Main effect plots -> Pareto plot
-> Interaction plots-> normal plots / active contrast /
gambler plots -> diagnosis of feedbacks and interactionsMain
effect plots -> Pareto plot -> Interaction plots-> normal
plots / active contrast / gambler plots -> diagnosis of
feedbacks and interactions
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- Summary of OAT Analysis - Linear results -Interactions need to
be extracted in a ad- hoc manner / subjectively -Results state what
is happening and not how it is happening in the analysis
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- Analysis of Variance
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- Why land surface changes in tropics matter? The answer could be
in the soil moisture availability
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- Relevance of the results to Biosphere Atmosphere Interaction
studies Process - based analysis of the physical parameterizations
for every vegetation - typeProcess - based analysis of the physical
parameterizations for every vegetation - type Extracted direct as
well as interactive feedbacksExtracted direct as well as
interactive feedbacks Interaction effects can be equated to the
indirect effects of CO2 doubling (though not causally, often as
empirical corrections)Interaction effects can be equated to the
indirect effects of CO2 doubling (though not causally, often as
empirical corrections) Previous studies suggested, CO2 doubling
will affect C3 vegetation and may not affect C4. This may be true
only for the direct effects but considering interactions, both C3
and C4 vegetation appears to be significantly affected by CO2
changesPrevious studies suggested, CO2 doubling will affect C3
vegetation and may not affect C4. This may be true only for the
direct effects but considering interactions, both C3 and C4
vegetation appears to be significantly affected by CO2 changes CO2
doubling effects should not be discussed without considering soil
moisture statusCO2 doubling effects should not be discussed without
considering soil moisture status
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- Carbon Assimilation Rates are intrinsically linked with soil
moisture availabilityCarbon Assimilation Rates are intrinsically
linked with soil moisture availability Used coupled GEM based
outcome over all the nine SiB2 vegetation types to prove the
hypothesisUsed coupled GEM based outcome over all the nine SiB2
vegetation types to prove the hypothesis landscape can be a source
/ sink depending on the soil moisture statuslandscape can be a
source / sink depending on the soil moisture status Need to
consider interactions explicitly while analyzing Biosphere
Atmosphere InteractionsNeed to consider interactions explicitly
while analyzing Biosphere Atmosphere Interactions
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- Hydrological Carbon Feedbacks CO2 issues need implicit
hydrological considerations e.g. Ball Berry carbon assimilation /
transpiration model Gs = (m. An / Cs. RHs ) + b m, b - specie
specific constants An - Net Assimilation Cs - CO2 at leaf surface
RHs - humidity at leaf surface Carbon Assimilation is linked with
transpiration (which is linked with surface energy balance, and so
on) Possible to scale carbon effects via hydrological
considerations
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- Differential Vegetation Characteristics based SGS heterogeneity
consideration For the example considered (C3 and C4 grassland)For
the example considered (C3 and C4 grassland) Air temperature and
SHF related impacts were minimal Transpiration and LHF effects were
significantly affected Largest errors could be in carbon budget or
environmental (air pollution, hydrometeorological) studies Results
are from a One - At - Time (OAT) approach (without
interactions)Results are from a One - At - Time (OAT) approach
(without interactions)
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- C3 - C4 Interactions Use Factor Separation approach (Stein and
Alpert, 1993) for CO2 (present day, doubled), soil moisture (wet,
dry), soil texture (clay, loam), and vegetation type (C3, C4)
changes
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- Differential Vegetation Characteristics based SGS heterogeneity
consideration FacSep study identified two as well as higher order
interactions are significantly active with C3 - C4 vegetation based
DVCFacSep study identified two as well as higher order interactions
are significantly active with C3 - C4 vegetation based DVC
Interaction term do not show expected compensation (SHF and LHF
main effects could be inversely linked but the interactions could
be directly related)Interaction term do not show expected
compensation (SHF and LHF main effects could be inversely linked
but the interactions could be directly related)
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- Differential Vegetation Characteristics based SGS heterogeneity
consideration Are all the interactions similarly important?Are all
the interactions similarly important? Need to identify
statistically significant interactions Fractional Factorial
Analysis performed for 12-h averaged (day time) coupled GEM outcome
What is the effect of CO 2 doubling on such a DVC based SGS
heterogeneity?What is the effect of CO 2 doubling on such a DVC
based SGS heterogeneity?
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- Differential Vegetation Characteristics based SGS heterogeneity
consideration Numerous conditions of C3 - C4 like DVC interaction
analyzed under varying soil moisture, CO 2, and soil texture
conditionsNumerous conditions of C3 - C4 like DVC interaction
analyzed under varying soil moisture, CO 2, and soil texture
conditions Analysis confirms interactions are an important
component of the carbon budget (not simply addition as often
perceived, but also need to consider higher order terms to identify
missing components)Analysis confirms interactions are an important
component of the carbon budget (not simply addition as often
perceived, but also need to consider higher order terms to identify
missing components) DVC errors were reduced under doubling of CO 2
conditions (and when resources are not limiting), and significantly
persist otherwise.DVC errors were reduced under doubling of CO 2
conditions (and when resources are not limiting), and significantly
persist otherwise. Anomaly results (CO 2 doubling exercises need to
be re-evaluatedAnomaly results (CO 2 doubling exercises need to be
re-evaluated Simple area - averaging is not adequate and may lead
to incorrect delineation of carbon source - sinks as well as
moisture budget.Simple area - averaging is not adequate and may
lead to incorrect delineation of carbon source - sinks as well as
moisture budget.
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- Variation of the effective variables based on the C3 C4 area
averaging and explicit interaction consideration.
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- (a) Area - Averaged, and (b) Interaction effect (~ 20 % of the
direct effect)
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- Effective Parameter / relations for C3 - C4 like DVC based SGS
heterogeneity Rs eff = a 3.C3 + a 4.C4 + max {0.35(a 3.C3), 1.5(a
4.C4)} An eff = a 3 C3 + a 4 C4 max{0.5(a 3.C3), 0.25(a 4.C4)} Etr
eff = a 3.C3 + a 4.C4 max{0.33(a 3.C3), 0.2(a 4.C4)} LHF eff = a
3.C3 + a 4.C4 max{0.25(a 3.C3), 0.15(a 4.C4)} SHF eff = a 3.C3 + a
4.C4 + max{0.2(a 3.C3), 0.3(a 4.C4)}
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- Future Directions Interactions are dominant in atmospheric
processesInteractions are dominant in atmospheric processes Methods
are still evolving to extract and analyze themMethods are still
evolving to extract and analyze them Two of the popular methods
Fractional Factorial and Factor Separation appear promisingTwo of
the popular methods Fractional Factorial and Factor Separation
appear promising Fractional Factor Separation also
evolvingFractional Factor Separation also evolving Results function
of sampling?Results function of sampling? Need for using these
observations in field experiments and then for parameterization
testingNeed for using these observations in field experiments and
then for parameterization testing Question Observations..Question
Observations..
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- Brain Storming Exercise Develop an interaction explicit
scenario which you think is not well understood?Develop an
interaction explicit scenario which you think is not well
understood? Describe how interaction explicit approaches may help
explain the feedbacks and interactions
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