1 / 22

SRNWP Lead Centre Report on Data Assimilation 2005 for EWGLAM/SRNWP Annual Meeting 2005

SRNWP Lead Centre Report on Data Assimilation 2005 for EWGLAM/SRNWP Annual Meeting 2005 3-5 October 2005, Ljubljana, Slovenia. Mike Bush NWP. SRNWP/Met Office/HIRLAM workshop in Exeter Global model 4D-VAR NAE model 4D-VAR U.K 4km model 3D-VAR. SRNWP/Met Office/HIRLAM Workshop.

karli
Download Presentation

SRNWP Lead Centre Report on Data Assimilation 2005 for EWGLAM/SRNWP Annual Meeting 2005

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. SRNWP Lead Centre Report on Data Assimilation 2005 for EWGLAM/SRNWP Annual Meeting 2005 3-5 October 2005, Ljubljana, Slovenia Mike Bush NWP

  2. SRNWP/Met Office/HIRLAM workshop in Exeter • Global model 4D-VAR • NAE model 4D-VAR • U.K 4km model 3D-VAR

  3. SRNWP/Met Office/HIRLAM Workshop • Joint SRNWP/Met Office/HIRLAM Workshop on High resolution data assimilation: towards 1-4km resolution • Held at the Met Office, Exeter 15 -17 November 2004 • What is different for the convective scale? • High resolution observations – their assimilation & utility • Assimilating cloud and precipitation observations • Analysis techniques, 3D-Var and error covariances • 4D-Var issues

  4. SRNWP/Met Office/HIRLAM workshop in Exeter • Global model 4D-VAR • NAE model 4D-VAR • U.K 4km model 3D-VAR

  5. 4D-VAR: The Perturbation Forecast (PF) model • PF model is an approximation to the tangent linear model • Dynamical core: • Start from continuous equations • ECMWF start from the discrete equations for the dynamical core • scale analysis • Choose appropriate terms at an asymptotic limit • then discretize • Physics: • Simplified physics

  6. 4D-VAR : PF model physics • Simplified physics: • Boundary layer: friction and vertical diffusion of heat and momentum (following Buizza). • Latent heating scheme (simplified microphysics). • No convection. • No radiation. • No gravity wave drag

  7. Global 4D-VAR • G33 5th October 2004 • Introduction of 4D-VAR. • Single outer loop • Half model resolution (N108) • Positive benefit – greatest impact in the SH • Satellite data is asynoptic and so particularly suited to 4D-VAR

  8. PMSL NH T+24 RMS Error against analysis 4DVAR 4DVAR 8

  9. 500hPa Height SH T+24 RMS Error against analysis 4DVAR 9

  10. 250hPa Wind SH T+72 RMS Vector Error vs analysis 4DVAR 4DVAR 10

  11. SRNWP/Met Office/HIRLAM workshop in Exeter • Global model 4D-VAR • NAE model 4D-VAR • U.K 4km model 3D-VAR

  12. NAE 4D-VAR: how to treat the boundaries • Increments zero at the lateral boundaries • Weights of 0, 0, 0, 0, 0, 0.25, 0.5, 0.75 applied going away from the rim • Simple but cheap way of treating the boundaries • HIRLAM have a more sophisticated system using periodic boundaries • Only obs within ½ gridlength of the boundary are excluded

  13. NAE 4D-VAR testing • 2-week run at half-resolution was completed • Encouraging benefit to PMSL verification. • Other fields are more neutral/slight detriments. • Global 4DVAR does not assimilate screen level data, nor does it assimilate hourly sequences of the surface obs that it does use. • These new aspects of regional 4DVAR might need further tuning. • No problems with using persistence as the PF forecast for aerosol in the 2-week run • This means that experiments with visibility assimilation can go ahead

  14. NAE 3D-VAR vs 4D-VAR PMSL Bias and RMSE 14

  15. 3D-VAR vs 4D-VAR Temperature Bias and RMSE 15

  16. SRNWP/Met Office/HIRLAM workshop in Exeter • Global model 4D-VAR • NAE model 4D-VAR • U.K 4km model 3D-VAR

  17. U.K 4km model: 3D-VAR • Initial solution is to introduce 3D-VAR assimilation system (plus Analysis Correction scheme for cloud and precipitation) • So far 12 case studies run from June – September 2005 • Parallel Suite running scheduled for October 2005 • Implementation scheduled for November 2005 • Later upgrade will address consistency with larger scale increments from the driving model

  18. U.K 4km model 3D-VAR impact: PMSL

  19. U.K 4km model 3D-VAR impact: 1.5m Temperature

  20. U.K 4km model 3D-VAR impact: 10m wind

  21. U.K 4km model 3D-VAR impact: cloud

  22. Questions?

More Related