TheNa'onalCenterforAtmosphericResearchissponsoredbytheNa'onalScienceFounda'on.Anyopinions,findingsandconclusionsorrecommenda'onsexpressedinthispublica'onarethoseoftheauthor(s)anddonotnecessarilyreflecttheviewsoftheNa'onalScienceFounda'on.

©UCAR

DARTTutorialSec'on15:DARTExperiments:ControlandDesign

DARTobserva'onsequence(obs_sequence)files

Containa!me-orderedlistofobserva'ondefini'ons:1.Typeofobserva'on(radiosondetemperature,radarreflec'vity),2.Loca'onofobserva'on,3.Timeofobserva'on,4.Observa'onerrorvariance,5.Addi'onalstuffforcomplexobserva'ontypes,6.Qualitycontrolvalues.Whendrivingfilterassimila'on,alsocontainobservedvalues.

(Anobserva'onsequencecanhave0ormorevaluesassociatedwitheachobserva'on;sec'on17).

DARTTutorialSec'on15:Slide2

DARTexperimentsaredrivenbyinputobserva'onsequences

model_moddefinesashortest_!me_between_assimila!ons,Δt.Ini'al'meofensemble(frominputfileornamelist)isti.

Δt/2 Δt/2

Δt/2 Δt/2

Δt/2 Δt/2

ModelAdvance

ModelAdvance

ti

ti+Δt

ti+2Δt

Allobserva'onsinthis'meintervalupdateprioratti.

Filtercon'nuesun'lallobserva'onsinsequencehavebeenused.Firstobserva'oncanNOTbeearlierthanfirst‘window’.Ifa‘window’hasnoobserva'ons,noassimila'onisdone.

DARTTutorialSec'on15:Slide3

DARTexperimentsaredrivenbyinputobserva'onsequences

Thiscapabilityistoolimited:Wouldliketoallow:1.Dynamicallyadjus'ngmodelΔtformodelswiththiscapability;2.WindowwidthsthatcouldbelessthanΔt;

Δt/2 Δt/2

Δt/2 Δt/2

Δt/2 Δt/2

ModelAdvance

ModelAdvance

ti

ti+Δt

ti+2Δt

Allobserva'onsinthis'meintervalupdateprioratti.

3.Timeinterpola'onforwardoperators.

DARTTutorialSec'on15:Slide4

Dealingwithmodelswithmul'-level'medifferencing

t

t

Example:Leapfrog

1.Canjust‘restart’fromsingle'me-leveladereachassimila'on.

Thiscanleadtonumericalinstabilityif‘restarts’toofrequent.Limitofdenseobserva'onsin'me,becomesforwarddifferencing..

DARTTutorialSec'on15:Slide5

Dealingwithmodelswithmul'-level'medifferencing

t

Example:Leapfrog

2.Canexpanddefini'onofmodelstatetoincludemul'ple'mes.Statevectorincludes'mestiandti+1forobserva'onswith

'mesinthisinterval.Thiscanimproveperformance.Alsopermitseasy'meinterpola'onforwardoperators.Worksincurrentimplementa'onifmodel_modinterfaceismodified.Mostmodelsdonotimplementthiscapability.

ti ti+1

DARTTutorialSec'on15:Slide6

Experimenttypes

1.Realdatafilteringassimila'ons:observa'onsfrominstruments.2.ObservingSystemSimula'onExperiments(OSSEs):

Observa'onsaresynthe'c.Modelintegra'onsubs'tutesfortruth.Forwardoperatorforeachobserva'onappliedtotruthstate.RandomsamplefromN(0,σobs)addedin.σobsfromobserva'onsequencefile.

3.ObservingSystemExperiments(OSEs):

Userealobserva'ons,butwithholdsomewithpurpose.

DARTTutorialSec'on15:Slide7

Experimenttypes

4.MixedOSEs/OSSEs:Addsynthe'cobserva'onstorealobserva'ons.‘Truth’forsynthe'ccomesfrommodelintegra'onfromlastassimilatedstatees'mate.

5.Observa'ontarge'ng:

GivenOSEorOSSE,Addobserva'onsinfuturetoimprovefutureperformance,Alreadydoneopera'onallyforweatherpredic'on.Whereshouldaplaneflytogetmostvaluableobserva'ons?

6.Smoothing:notcurrentlysupportedinDARTManhagan

Useobserva'onsinfuturetoimprovestatees'mate,Canbeturnedonwith&smoother_nml:num_lags.

DARTTutorialSec'on15:Slide8

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'on15:Slide9