1 / 62

WRF-EnKF Lightning Assimilation Real-Observation Experiments Overview

WRF-EnKF Lightning Assimilation Real-Observation Experiments Overview. Cliff Mass, Greg Hakim, Phil Regulski, Ryan Torn Department of Atmospheric Sciences University of Washington February 15, 2008. Overview. WRF-EnKF Overview Lightning Assimilation Technique Review Project Review

elise
Download Presentation

WRF-EnKF Lightning Assimilation Real-Observation Experiments Overview

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. WRF-EnKF Lightning Assimilation Real-Observation ExperimentsOverview Cliff Mass, Greg Hakim, Phil Regulski, Ryan Torn Department of Atmospheric Sciences University of Washington February 15, 2008

  2. Overview • WRF-EnKF Overview • Lightning Assimilation Technique Review • Project Review • Model Estimate Experiments • Case Studies • December 2002 • October 2004 • November 2006 • Conclusions • In-progress/Future work

  3. The Use of EnKF for Lightning Assimilation • In this work the ensemble Kalman filter is applied using the WRF model (WRF-EnKF). • The covariance statistics from EnKF that spread the impact of observations are flow-dependent • Lightning observations are ideal to provide WRF-EnKF with more observational information in areas with few in situ observations (e.g. Pacific Ocean) • Impact of lightning observations will propagate into areas of high forecast impact (West coast and beyond)

  4. Lightning Assimilation Techniques • Original Lightning Experiment (LTNG2) • NLDN/LR lightning strike is detected • Lightning strike is converted into lightning rate from nearby LTNG observations • Lightning rate converted into convective rainfall rate using Pessi/Businger convective rain rate/lightning rate relationship • Convective rainfall (mm) is assimilated into WRF-EnKF • Successful test on Dec. 2002 case

  5. Lightning Assimilation Techniques • Minimal Counting Technique Lightning Experiment (LTNG4) • NLDN/LR lightning strike is detected • Lightning strike is converted into lightning rate from nearby LTNG observations • Once any nearby lightning strikes are used to calculate a lightning density they are no longer available as an assimilation point (although they are still used to calculate LTNG densities) • Lightning rate converted into convective rainfall rate using Pessi/Businger convective rain rate/lightning rate relationship • Convective rainfall (mm) is assimilated into WRF-EnKF • Successful testing on Dec. 2002 case

  6. Project Review • Research Completed • Dec. 2002 Test Case - Analysis and 12-hr Forecasts • Oct. 2004 Test Case - Analysis • Nov. 2006 Test Case - Analysis • Modifications to LTNG2 and LTNG4 models to improve analysis and forecasts • In-progress • Forecast analysis of Oct. 2004 Test Case • Forecast analysis of Nov. 2006 Test Case • 1-hr assimilation of cumulative convective rain rate data (previously using 6-hr cumulative totals) for LTNG2 and LTNG4 models

  7. Recent ExperimentsCan we further improve Dec 2002 performance? • Model-estimate and observations of cumulative convective precipitation calculated by LTNG density occasionally have large innovations leading to large increments in the model’s dynamical fields, possibly leading to locally unbalanced states • Set a upper bound on assimilated cumulative convective precipitation • Minimal Counting Technique Lightning Experiment (LTNG4) w/ modifications (LTNG5) • Same techniques as LTNG4 but with upper bound (18mm) • Less improvement in analysis and forecasts • Original LTNG4 still best performing model to test further on new regimes • Original Lightning Experiment (LTNG2) w/ modifications (LTNG6) • Same techniques as LTNG2 with upper bound (18mm) • Less improvement in analysis and forecasts • Original LTNG2 still best performing model to test further on new regimes • Another solution • Reduce cumulative value of convective rain assimilated from 6- to 1-hr block (In-progress)

  8. Case Study #1 – December 2002Minimum SLP recorded at extra-tropical cyclone’s center Limiting upper bound of cumulative convective precipitation degrades analysis performance (LTNG5/6) NCEP (black dashed) is NCEP subjective analysis

  9. Case Studies • Case #1: December 16-21, 2002 • Analysis • LTNG Analysis Impact of SLP, H500 fields • 12-hr Forecasts • GFS Analysis v. Fcst 12-hr Control • GFS Analysis v. Fcst 12-hr LTNG2 • GFS Analysis v. Fcst 12-hr LTNG4

  10. Major Findings • EnKF allows lightning to have a substantial influence on atmospheric analyses • The influence can be widespread over the domain

  11. Case Study #1 – December 2002Impact of Lightning Assimilation: LTNG2

  12. Case Study #1 – December 2002Impact of Lightning Assimilation: LTNG4

  13. Case Study #1 – December 2002Impact of Lightning Assimilation: LTNG2

  14. Case Study #1 – December 2002Impact of Lightning Assimilation: LTNG4

  15. Case Study #1 – December 2002Impact of Lightning Assimilation: LTNG2

  16. Case Study #1 – December 2002Impact of Lightning Assimilation: LTNG4

  17. Case Study #1 – December 2002Impact of Lightning Assimilation: LTNG2

  18. Case Study #1 – December 2002Impact of Lightning Assimilation: LTNG4

  19. Case Study #1 – December 2002Impact of Lightning Assimilation: LTNG2

  20. Case Study #1 – December 2002Impact of Lightning Assimilation: LTNG4

  21. Case Study #1 – December 2002Impact of Lightning Assimilation: LTNG2

  22. Case Study #1 – December 2002Impact of Lightning Assimilation: LTNG4

  23. Case Study #1 – December 2002Impact of Lightning Assimilation: LTNG2

  24. Case Study #1 – December 2002Impact of Lightning Assimilation: LTNG4

  25. The Impact on Forecasts Were Mixed

  26. Case Study #1 – December 200212-hr Forecast Comparison: Control

  27. Case Study #1 – December 200212-hr Forecast Comparison: LTNG2

  28. Case Study #1 – December 200212-hr Forecast Comparison: Control

  29. Case Study #1 – December 200212-hr Forecast Comparison: LTNG4

  30. Case Study #1 – December 200212-hr Forecast Comparison: Control

  31. Case Study #1 – December 200212-hr Forecast Comparison: LTNG2

  32. Case Study #1 – December 200212-hr Forecast Comparison: Control

  33. Case Study #1 – December 200212-hr Forecast Comparison: LTNG4

  34. Case Study #1 – December 200212-hr Forecast Comparison: Control

  35. Case Study #1 – December 200212-hr Forecast Comparison: LTNG2

  36. Case Study #1 – December 200212-hr Forecast Comparison: Control

  37. Case Study #1 – December 200212-hr Forecast Comparison: LTNG4

  38. Case Study #1 – December 200212-hr Forecast Comparison: Control

  39. Case Study #1 – December 200212-hr Forecast Comparison: LTNG2

  40. Case Study #1 – December 200212-hr Forecast Comparison: Control

  41. Case Study #1 – December 200212-hr Forecast Comparison: LTNG4

  42. Case Studies • Case #2: October 4-7, 2004 • Analysis • LTNG Analysis Impact of SLP, H500 fields • Number of LTNG strikes during test case is much smaller than Dec. 2002 case

  43. Case Study #2 – October 2004Impact of Lightning Assimilation: LTNG4

  44. Case Study #2 – October 2004Impact of Lightning Assimilation: LTNG4

  45. Case Study #2 – October 2004Impact of Lightning Assimilation: LTNG4

  46. Case Study #2 – October 2004Impact of Lightning Assimilation: LTNG4

  47. Case Study #2 – October 2004Impact of Lightning Assimilation: LTNG4

  48. Case Study #2 – October 2004Impact of Lightning Assimilation: LTNG4

  49. Case Study #2 – October 2004Impact of Lightning Assimilation: LTNG4

  50. Case Study #2 – October 2004Impact of Lightning Assimilation: LTNG4

More Related