Initial and Lateral Boundary Condition Perturbations DET Module 2

Initial and Lateral Boundary Condition Perturbations

DET Module 2

Isidora Jankov

Acknowledgements: Joseph B. Olson, Steven Albers, Jun Du, Mozeheng Wei, Brian Etherton, Adam Clark, Cliff Mass, Yuejian Zhu and the rest of the DET team

OverviewOverview

• Objectives• Current Status• Community Examples• Options for the first year activities• Options for testing• Tentative timeline• Preliminary results

ObjectiveObjectiveCreate infrastructure that allows for testing of

different methods to capture analysis uncertainty.

Porting NCEP/EMC SREF system as a benchmark for testing.

Testing of various community developed methods for creation of Initial Condition (IC) and Lateral Boundary Condition (LBC) perturbations.

Working with NCEP and other agencies on transition of selected methods to operations.

Current International Current International StatusStatus

Different centers use different approaches to ICs and LBCs problem. Usually the initial and LBC question for regional EFS is addressed by using the corresponding global EFS.

UK Met Office:◦ The initial condition perturbations for global EFS are generated by using the Ensemble Transform Kalman Filter (ETKF) approach (Bishop et al. 2001).◦ Originally the global EFS was used to provide ICs and LBCs to the regional EFS by simple interpolation to LAM higher resolution grid (dynamical downscaling). ◦ Regional ETKF used for a while. Based on the Bowler and Mylne 2009 study decision was reversed back to use of simple interpolation.

Environment Canada:◦ The initial condition perturbations for global EFS generated by using the Ensemble Kalman Filter (EnKF) approach. ◦ Simple interpolation currently in place. An effort on producing regional EnKF initial condition perturbations has started.

Current NCEP/EMC StatusCurrent NCEP/EMC Status Breeding technique for Global Ensemble Forecasting

System (GEFS) – 1992 Breeding technique for Regional EFS – 2000 Ensemble Transform with Rescaling (ETR) for GEFS -

2006 ETR has not been implemented for the regional EFS yet

(this option will be explored). Currently there is an inconsistency between Global and Regional EFS.

P1 forecast

P4 forecastP3 forecast

P2 forecast

t=t0 t=t2t=t1

Rescaling

Courtesy of Yuejian Zhu, Richard Wobus, Mozheng Wei, Bo Cui and Zoltan Toth

ETR with Rescaling

P1, P2, P3, P4 are orthogonal vectors

To centralize all perturbed vectors (simplex approach: sum of all vectors are equal to zero)

Scaling down by applying climatologically fixed mask

The direction of vectors is tuned by ETR.

Some of the community Some of the community examplesexamples

Ensemble IC/LBC

CAPS NAM 12km + 3D VAR ARPS assimilation/ SREF

RENCI RUC+NAM+LAPS/NAM

HMT LAPS /GEFS

University of Washington 1) World NWP systems2) EnKF

JME NCAR and AFWA EnKF/ETKF

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Options Year 1Options Year 1

• Set up basic infrastructures for using global EFS to drive regional EFS (initial perturbations created by using the Ensemble Transform with Rescaling (ETR))… e.g. UK Metoffice and Environment Canada simple interpolation technique

• Create infrastructure and test cycling approach when using GEFS as a step beyond the simple interpolation.

• Work on getting ETR ESMF compatible.

For the sake of compatibility between Global and Regional EFS

simple interpolation approach will be compared to the cycling approach

The upgraded version of the regional EFS (SREF) will be

Placed on the DTC systems

04/20/23 8

DET IC/LBC Perturbation Module

Candidates for TestingCandidates for TestingRegional EnKFRegional ETKFUse of quasi-orthogonal perturbations

for both global and regional components of the current NCEP/EMC system

Regional ETR Suggestions are welcome !Collaboration with the NCAR GSI group

on data assimilation issues

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Tentative timeline Tentative timeline

Year 1 – Detailed plan for infrastructure and preliminary testing of the cycling approach.

Year 2 – Implementation of additional perturbation methods and testing of user’s community requests.

Year 3 – Continuation of testing community-developed techniques and transitioning of promising techniques to NCEP for operational consideration.

Cycling Initial Cycling Initial PerturbationsPerturbations

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00Z 06Z

LAM Forecast

Global Model Forecast

Global Model Analysis interpolated on LAM grid

Perturbation

Legend

Forecast Time

Nested domain: • Outer/inner nest grid spacing 9 and 3 km, respectively • IC perturbations applied only to the outer domain using the GFS control run.

HMT Ensemble Integration Domains

00hr

03hr

06hr

Wind SpeedJuly 30 2010 00UTC

LAPS CYC NOCYC

CYC

12hr

~15kt

~25kt

~25kt

500mb WindJuly 30 2010 12UTC

NOCYC

12hr

~15kt

~30kt

~25kt

500mb WindJuly 30 2010 12UTC

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Cloud CoverageJuly 30 2010 00UTC

00hr

03hr

06hr

LAPS CYC NOCYC

Questions for the Questions for the CommunityCommunityHow should the infrastructure be

organized to accommodate testing of various IC and LBC perturbation approaches?

What options for IC and LBC

perturbations would the community suggest to be developed/tested?

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