dart tutorial sec’on 10: regression and non-linear effects · 2018-11-30 · dart-compliant...
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DARTTutorialSec'on10:RegressionandNon-linearEffects
Upda'ngaddi'onalpriorstatevariables
Twoprimaryerrorsources:1.Linearapproxima'onisinvalid.
Substan'alnonlinearityin‘true’rela'onoverrangeofprior.2.Samplingerrorduetonoise(we’vealreadylookedatthis).
Eveniflinearrela'on,sampleregressioncoefficientimprecise.Mayneedtoaddressbothissuesforgoodperformance.
DARTTutorialSec'on10:Slide2
Nonlinearrela'onsbetweenvariables:Sor'ngincrements
SupposepriorsamplehasNOnoise.But,rela'onbetweenun/observedvariablesisnon-linear.
DARTTutorialSec'on10:Slide3
Nonlinearrela'onsbetweenvariables:Sor'ngincrements
SupposepriorsamplehasNOnoise.But,rela'onbetweenun/observedvariablesisnon-linear.Updateobservedsampleandcomputeincrements.
DARTTutorialSec'on10:Slide4
Nonlinearrela'onsbetweenvariables:Sor'ngincrements
SupposepriorsamplehasNOnoise.But,rela'onbetweenun/observedvariablesisnon-linear.Regressionerrorvarieswithvalueofobservedvariable.
DARTTutorialSec'on10:Slide5
Nonlinearrela'onsbetweenvariables:Sor'ngincrements
SupposepriorsamplehasNOnoise.But,rela'onbetweenun/observedvariablesisnon-linear.Regressionerrorvarieswithvalueofobservedvariable.Smallerincrementshavesmallerexpectederrors.
DARTTutorialSec'on10:Slide6
Nonlinearrela'onsbetweenvariables:Sor'ngincrements
SupposepriorsamplehasNOnoise.But,rela'onbetweenun/observedvariablesisnon-linear.Pairingbetweenpriorandposteriorsampleofobservedvariablecanbeviewedasarbitrary.Posteriorissamesamplehoweverit’spaired.
DARTTutorialSec'on10:Slide7
Nonlinearrela'onsbetweenvariables:Sor'ngincrements
SupposepriorsamplehasNOnoise.But,rela'onbetweenun/observedvariablesisnon-linear.Canminimizeincrementsbychangingpairing.Sor'ngpriorandposteriorandpairingsamplesminimizesonenormofincrementsize(coulddoothermethods)
DARTTutorialSec'on10:Slide8
Nonlinearrela'onsbetweenvariables:Sor'ngincrements
SupposepriorsamplehasNOnoise.But,rela'onbetweenun/observedvariablesisnon-linear.Canminimizeincrementsbychangingpairing.Sor'ngpriorandposteriorandpairingsamplesminimizesonenormofincrementsize(coulddoothermethods)
DARTTutorialSec'on10:Slide9
Nonlinearrela'onsbetweenvariables:Sor'ngincrements
SupposepriorsamplehasNOnoise.But,rela'onbetweenun/observedvariablesisnon-linear.Resul'ngregressionerrorisminimized.Impactofsor'ngcanbeverylargewhenposteriorselectedby‘random’algorithms.
DARTTutorialSec'on10:Slide10
Nonlinearrela'onsbetweenvariables:Sor'ngincrements
SupposepriorsamplehasNOnoise.But,rela'onbetweenun/observedvariablesisnon-linear.Resul'ngregressionerrorisminimized.Impactofsor'ngcanbeverylargewhenposteriorselectedby‘random’algorithms.
DARTTutorialSec'on10:Slide11
Nonlinearrela'onsbetweenvariables:Sor'ngincrements
Canseethisimpactnicelyin9varmodel.Tryfilter_kind=2inassim_tools_nmlwith:
sort_obs_inc=.true.(incrementsminimized)andsort_obs_inc=.false.
Examinetheamountofnoiseindifferent'meseries.ImpactonRMSmaynotbewhatwasexpected.Theremaybesurprisesinotherlow-ordermodelswhentryingthis.
DARTTutorialSec'on10:Slide12
models/9var/work/
&assim_tools_nml filter_kind = 2 sort_obs_inc = .false. …
Nonlinearrela'onsbetweenvariables:Sor'ngincrements
AlsocanexamineinLorenz96.Tryfilter_kind=2inassim_tools_nmlwith:
sort_obs_inc=.true.(incrementsminimized)andsort_obs_inc=.false.
Tryacasewithnolocaliza'on(largecutoff)Varyinfla'onwithandwithoutthesor'ng.
DARTTutorialSec'on10:Slide13
models/lorenz_96/work/
&assim_tools_nml filter_kind = 2 sort_obs_inc = .true. cutoff = 1000000.0 …
Nonlinearrela'onsbetweenvariables:Localregression
Priorsampleisnoisy.Un/observedrela'onisnon-linear.DoingglobalregressionwouldbeBADhere.Candoregressiononlyforpointsthatlieinrangeofupdateincrement.Couldalsopicklocalsetsinotherways.
DARTTutorialSec'on10:Slide14
Nonlinearrela'onsbetweenvariables:Localregression
Priorsampleisnoisy.Un/observedrela'onisnon-linear.Forlargerensembles,localregressionscanworkwell.Errorislargestwheresignalisweakest(nearboeomofparabolahere).
DARTTutorialSec'on10:Slide15
Nonlinearrela'onsbetweenvariables:Localregression
Priorsampleisnoisy.Un/observedrela'onisnon-linear.Assamplesizedecreases,errorgrows.(Exceptwhereitwasroeentostart).Applica'onswherelocalregressionisusefulareunknowntome.
DARTTutorialSec'on10:Slide16
Nonlinearrela'onsbetweenvariables:Localregression
DARTdoesnotcurrentlysupportlocalregressionwithoutcodemodifica'on.
DARTTutorialSec'on10:Slide17
1. FilteringForaOneVariableSystem2. TheDARTDirectoryTree3. DARTRun>meControlandDocumenta>on4. Howshouldobserva>onsofastatevariableimpactanunobservedstatevariable?
Mul>variateassimila>on.5. ComprehensiveFilteringTheory:Non-Iden>tyObserva>onsandtheJointPhaseSpace6. OtherUpdatesforAnObservedVariable7. SomeAddi>onalLow-OrderModels8. DealingwithSamplingError9. MoreonDealingwithError;Infla>on10. RegressionandNonlinearEffects11. Crea>ngDARTExecutables12. Adap>veInfla>on13. HierarchicalGroupFiltersandLocaliza>on14. QualityControl15. DARTExperiments:ControlandDesign16. Diagnos>cOutput17. Crea>ngObserva>onSequences18. LostinPhaseSpace:TheChallengeofNotKnowingtheTruth19. DART-CompliantModelsandMakingModelsCompliant20. ModelParameterEs>ma>on21. Observa>onTypesandObservingSystemDesign22. ParallelAlgorithmImplementa>on23. Loca'onmoduledesign(notavailable)24. Fixedlagsmoother(notavailable)25. Asimple1Dadvec>onmodel:TracerDataAssimila>on
DARTTutorialIndextoSec'ons
DARTTutorialSec'on10:Slide18