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Improving the Validation and Prediction of Tropical Cyclone Rainfall

Project funded by JHT to improve validation & prediction of TC rainfall, comparing models & observations for better forecast accuracy and developing modified prediction schemes.<br>

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Improving the Validation and Prediction of Tropical Cyclone Rainfall

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  1. Improving the Validation and Prediction of Tropical Cyclone Rainfall Timothy P. Marchok NOAA/GFDL Princeton, NJ Robert F. Rogers NOAA/AOML/HRD Miami, FL Robert E. Tuleya NOAA/NCEP/EMC/SAIC Camp Springs, MD 58th Interdepartmental Hurricane Conference, Charleston, SC March 1-5, 2004 * This project is being funded by the Joint Hurricane Testbed (JHT)

  2. Goals • Goal: Develop a set of rainfall validation schemes more suited specifically for TCs • Motivation: Conventional precip skill scores are often difficult to interpret in the context of tropical cyclones • Goal: Produce model QPF error statistics for historic U.S. landfalling storms. • Motivation: No systematic QPF verification has been done on NWS operational models for the specific subset of landfalling U.S. tropical cyclones • Goal: Develop a modified R-CLIPER that incorporates vertical shear & storm track data. • Motivation: Recent research has shown that including vertical shear information can add structure to R-CLIPER's currently symmetric rainfall distribution

  3. Outline • Standard QPF verifications • GFDL model: 1995-2002 storms; rain gauge data • NWS operational suite: 1998-2003 storms; Stage IV gridded rainfall analyses • Application of a new verification technique to Hurricane Isabel’s landfall • Future work

  4. GFDL Model QPF Verification, 1995-2002 • Verification data: Hourly & daily rain gauges • Gauge data within 800 km of storm track was summed over model forecast interval • Interpolated model storm total rainfall to gauge location • Average of 211 hourly gauges per storm • Nearly 1200 daily gauges per storm • Only used forecasts initialized at 12 UTC, to coincide with daily rain gauge network • All storms within ~24h of landfall

  5. U.S. Landfalling Cases for Model Evaluation NWS Operational Suite GFDL, R-CLIPER

  6. QPF Bias Scores: GFDL vs. R-CLIPER

  7. Equitable Threat Scores

  8. Model vs. obs correlation: A first guess at pattern matching

  9. Track error <-> QPF error

  10. Storm Intensity <-> QPF Error

  11. QPF verification for NWS model suite: 28 storms from 1998-2003 • GFDL, NCEP/GFS, NCEP/Eta, R-CLIPER, 2xR-CLIPER • GFDL 2003 version used for all 28 cases • Obs data: Hourly multi-sensor (radar, gauge) gridded data available online from NCAR • 2002-2003: NCEP/EMC Stage IV data • 1998-2001: NCEP/EMC Stage II data

  12. QPF Bias Scores

  13. QPF Equitable Threat Scores

  14. GFS: 0.65 Eta: 0.56 GFDL: 0.52 RCLIP: 0.47

  15. GFS: 0.65 Eta: 0.56 GFDL: 0.52 RCLIP: 0.47

  16. GFDL Stage IV GFS Eta

  17. GFDL Stage IV GFS Eta

  18. Rainfall statistics for observations and forecasts of 24-h rain from 12 UTC 18 to 12 UTC 19 September for Isabel (2003)

  19. Cumulative frequency (%) Frequency (%) PDF and CDF comparisons of rain flux binned by rain amount Plot of 24-h rain (in) from 12 UTC 18 to 12 UTC 19 September for Isabel (2003) for NPVU and R-CLIPER Stage IV R-CLIPER

  20. Cumulative frequency (%) Frequency (%) PDF and CDF comparisons of rain flux binned by rain amount Plot of 24-h rain (in) from 12 UTC 18 to 12 UTC 19 September for Isabel (2003) for NPVU and GFDL Stage IV GFDL

  21. Cumulative frequency (%) Frequency (%) PDF and CDF comparisons of rain flux binned by rain amount Plot of 24-h rain (in) from 12 UTC 18 to 12 UTC 19 September for Isabel (2003) for NPVU and GFS Stage IV GFS

  22. Cumulative frequency (%) Frequency (%) PDF and CDF comparisons of rain flux binned by rain amount Plot of 24-h rain (in) from 12 UTC 18 to 12 UTC 19 September for Isabel (2003) for NPVU and Eta Stage IV Eta

  23. 10 RCLIPER GFDL GFS ETA forecast R (in) 1 0.1 0.1 1 10 observed R (in) Probability-matched 24-h rain estimates from Stage IV data vs. R-CLIPER, GFDL, GFS, and Eta models for Hurricane Isabel 90% 90% 90% 10% 10% 10% 10%

  24. Summary & Future Plans • QPF error stats for landfalling TCs: • GFDL only: 1995-2002 vs. rain gauge data • NWS suite: 1998-2003 vs. gridded Stage IV data • Compare operational GFDL vs. 2003 GFDL for all storms, 1995-2003 • Development of a set of QPF verification schemes more suited to TCs • Apply a PDF/CDF method to TC rain flux • Use PDF/CDF method on NWS suite, 1998-2003 • Investigate other spatial-based methods? • Develop a modified R-CLIPER that incorporates vertical shear & storm track data (Year 2)

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