Vaisala/University of Washington Real-observation Experiments

Vaisala/University of Vaisala/University of WashingtonWashington

Real-observation Real-observation ExperimentsExperiments

Clifford Mass, Gregory Hakim,Clifford Mass, Gregory Hakim,Phil Regulski, Ryan Torn,Phil Regulski, Ryan Torn,

Jennifer FletcherJennifer FletcherDepartment of Atmospheric Sciences Department of Atmospheric Sciences

University of WashingtonUniversity of Washington

October 2006October 2006

Data Data AssimilationAssimilation

• Fusion of models & observations.Fusion of models & observations.– Need error statistics!Need error statistics!

• Spreads observational information.Spreads observational information.

• Analysis: Analysis: – smaller error than observations.smaller error than observations.– smaller error than model estimate of smaller error than model estimate of

obs. obs.

Data Assimilation in a Data Assimilation in a NutshellNutshell

prob of current stateprob of current stategiven all current and given all current and

past observationspast observations

prob of obs given current

state

prob of current state given all past observations.

Cyclic algorithm given new

observations model

Observation (Observation (greengreen) & Background () & Background (blueblue) ) PDFsPDFs

Analysis (Analysis (redred) PDF---higher density!) PDF---higher density!

More-Accurate ObservationMore-Accurate Observation

Less-Accurate ObservationLess-Accurate Observation

Ensemble Kalman Ensemble Kalman FilterFilter

1 2( , ,..., )e

b b b bNX x x x ' '1

1

Tb b b

e

P X XN

Crux: use an ensemble of fully non-linear forecasts to model the statistics of the background (expected value and covariance matrix).

Advantages

• No à priori assumption about covariance; state-dependent corrections.

• Ensemble forecasts proceed immediately without perturbations.

LR Lightning LR Lightning Real-Real-

Observation Observation ExperimentExperiment

Establish geographical domain for Establish geographical domain for Real-observation ExperimentReal-observation Experiment

• Dec 12-24, 2004Dec 12-24, 2004– Domain location that Domain location that

encompasses Pessi/Businger encompasses Pessi/Businger previously studied stormpreviously studied storm

• Pacific OceanPacific Ocean– Low observation density; Low observation density;

location of important storm location of important storm tracks; errors propagate tracks; errors propagate downwind to mainland downwind to mainland United StatesUnited States

• North America North America – High observation density; High observation density;

forecast improvement forecast improvement interest area; included to see interest area; included to see the impact of regions of low the impact of regions of low and high observation and high observation densitiesdensities

Real time observationsReal time observations

• Control caseControl case – Observation locations from real dataObservation locations from real data– RadiosondesRadiosondes– Surface stations (ASOS, ship, buoy)Surface stations (ASOS, ship, buoy)– ACARSACARS– Cloud drift-winds (Cloud drift-winds (no sat radiancesno sat radiances))

• Lightning experimentLightning experiment– Assimilation of convective rain rate Assimilation of convective rain rate

A Traditional Observation NetworkA Traditional Observation Network20041001182004100118

ACAR observations

Soundings

Surface observations

Experiment observationsExperiment observationsACARS Obs.ACARS Obs.

Experiment observationsExperiment observationsCloud Track Wind Obs.Cloud Track Wind Obs.

Experiment observationsExperiment observations

•Radiosonde Obs

•Surface Stations

Experiment Experiment observationsobservations

LTNG ObsLTNG Obs


LTNG ObsLTNG Obs


• Lightning assimilationLightning assimilation– Real LR LTNG strike is identifiedReal LR LTNG strike is identified– WRF-ENKF locates LTNG and feeds the WRF-ENKF locates LTNG and feeds the

experimental run the convective experimental run the convective precipitation from the Pessi convective precipitation from the Pessi convective rain rate/LTNG rate relationship at the rain rate/LTNG rate relationship at the LTNG coordinatesLTNG coordinates

Real-observation Real-observation ExperimentsExperiments

2-Week Experiment2-Week Experiment

• 100 by 86 grid points100 by 86 grid points

• 45-km resolution45-km resolution

• 33 vertical levels33 vertical levels

• 48 ensemble members48 ensemble members

• Assimilation every 6 hoursAssimilation every 6 hours

• Forecasts: 6, 12, 18, 24, 30, 36, 42 Forecasts: 6, 12, 18, 24, 30, 36, 42 and 48 hoursand 48 hours

2-Week Experiment2-Week Experiment

• WRF ensemble Kalman filter settingsWRF ensemble Kalman filter settings– Square root filter (Whitaker and Hamill, 2002)Square root filter (Whitaker and Hamill, 2002)– Horizontal localization – Gaspari and Cohn 5Horizontal localization – Gaspari and Cohn 5thth

order piecewiseorder piecewise– Fixed covariance perturbations to lateral Fixed covariance perturbations to lateral

boundariesboundaries– Constant uniform covariance inflation methodConstant uniform covariance inflation method– Localization radius – 2000kmLocalization radius – 2000km

Weather Pattern Weather Pattern Sea level pressureSea level pressure

Period characterized by extratropical cyclonePeriod characterized by extratropical cyclone

Weather Pattern Weather Pattern H500H500

Period with active weather pattern – Trough dominatedPeriod with active weather pattern – Trough dominated

Control ExperimentsControl Experiments

• Control experiment #1Control experiment #1– Not enough varianceNot enough variance– Increase inflation factorIncrease inflation factor

• Control experiment #2Control experiment #2– Still low varianceStill low variance– Switching inflation method from constant Switching inflation method from constant

inflation to Zhang methodinflation to Zhang method

• Control experiment #3Control experiment #3– Good varianceGood variance

Control ExperimentsControl ExperimentsControl Experiment #1 – Too low varianceControl Experiment #1 – Too low variance

Control ExperimentsControl ExperimentsControl Experiment #1 – Too low varianceControl Experiment #1 – Too low variance

Control ExperimentsControl ExperimentsControl Experiment #2– More variance but still too lowControl Experiment #2– More variance but still too low

Control ExperimentsControl ExperimentsControl Experiment #3– Acceptable varianceControl Experiment #3– Acceptable variance





• Control experiment #3Control experiment #3– Analysis varianceAnalysis variance

• H500mbH500mb

• T2m, T850mb, T300mbT2m, T850mb, T300mb

• Y300mbY300mb

• SLP, REFL, RAINC etcSLP, REFL, RAINC etc

– Observation verificationObservation verification• Rank histogramsRank histograms

• ProfileProfile

– Other…Other…







Test ExperimentsTest Experiments

• Coding LTNG assimilation into WRF-ENKFCoding LTNG assimilation into WRF-ENKF– Assimilated LTNG rateAssimilated LTNG rate– Transformed LTNG rate into convective rain Transformed LTNG rate into convective rain

raterate– Final coding Final coding – TestingTesting

• Experiment Run (LTNG assimilation - ~1.5 Experiment Run (LTNG assimilation - ~1.5 weeks)weeks)

• ComparisonsComparisons

Test ExperimentsTest ExperimentsExample of comparison productsExample of comparison products

• Analysis fieldsAnalysis fields– H500, SLP, WINDS, RAINCH500, SLP, WINDS, RAINC

• Forecast fieldsForecast fields– All forecast hoursAll forecast hours




SummarySummary• Where we are at…Where we are at…

– Data observations gathered from Dec Data observations gathered from Dec 20022002•Cloud track windsCloud track winds•ACARSACARS•SurfaceSurface•RadiosondesRadiosondes•LTNGLTNG

– Performed “control” runsPerformed “control” runs– Final stages of coding LTNG assimilation Final stages of coding LTNG assimilation

code for real observation WRF-ENKF code for real observation WRF-ENKF experimentsexperiments

– Ongoing statistical analysisOngoing statistical analysis

SummarySummary

• Future possibilitiesFuture possibilities– Alternative assimilation fieldsAlternative assimilation fields– In-house rain rate/LTNG rate relationshipIn-house rain rate/LTNG rate relationship– Different domainsDifferent domains– Other sample stormsOther sample storms

6-month goals6-month goals

• Real-time lightning data feed into UW-Real-time lightning data feed into UW-ATMS WRF-ENKF systemATMS WRF-ENKF system

• OSSE DE simulations OSSE DE simulations

• Robust and flexible OSSE and real Robust and flexible OSSE and real observation experiment systemsobservation experiment systems– Creation of flexible LTNG assimilation modules Creation of flexible LTNG assimilation modules

so new experiments can be quickly altered in so new experiments can be quickly altered in parameter fileparameter file

– Other… suggestions and comments =)Other… suggestions and comments =)

Documents

Vaisala/University of Washington Real-observation Experiments