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The NOAA Rapid Update Cycle (RUC) 1-h assimilation cycle

Stan Benjamin Steve Weygandt John Brown NOAA Forecast Systems Lab – Boulder CO, USA. The NOAA Rapid Update Cycle (RUC) 1-h assimilation cycle. GOAL: Provide high-frequency (1h) mesoscale 3-d analyses and short-range (1-12+h) forecasts for aviation, severe weather, hydrology, ….

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The NOAA Rapid Update Cycle (RUC) 1-h assimilation cycle

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  1. Stan Benjamin Steve Weygandt John Brown NOAA Forecast Systems Lab – Boulder CO, USA The NOAA Rapid Update Cycle (RUC) 1-h assimilation cycle • GOAL: • Provide high-frequency (1h) mesoscale 3-d analyses and short-range (1-12+h) forecasts for aviation, severe weather, hydrology, … WWRP Symposium -- Nowcasting & Very Short Range Forecasting – 8 Sept 2005 – Toulouse, France RUC web site- http://ruc.fsl.noaa.gov

  2. 3DVAR 3DVAR 3DVAR 3DVAR 3DVAR Obs Obs Obs Obs Obs RUC Hourly Assimilation Cycle 1-hr fcst 1-hr fcst 1-hr fcst 1-hr fcst 1-hr fcst 1-hr fcst Background Fields Analysis Fields Time (UTC) 11 12 13 14 15 16

  3. 12-h fcst 12-h fcst 3DVAR 3DVAR 3DVAR 3DVAR 3DVAR Obs Obs Obs Obs Obs RUC Hourly Assimilation Cycle + Forecasts > 1h 9-hr fcst 9-hr fcst 9-hr fcst 9-hr fcst Background Fields Analysis Fields Time (UTC) 11 12 13 14 15 16 Run-time at NCEP for RUC 12h fcst – 17 min

  4. RUC Obs Sources - experimental 13km RUC -- As of 6 Sept 05

  5. RUC20 • Wind forecast • Accuracy • Sept-Dec • 2002 6 9 1 3 12 Analysis ~ ‘truth’ 6 8 10 12 (kts) Verification against rawinsonde data over RUC domain RMS vector difference (forecast vs. obs) RUC is able to use recent obs to improve forecast skill down to 1-h projection for winds

  6. Application of Digital Filter Initialization (DFI) in RUC Model • Critical for 1-h assimilation cycle • 45 min forward, 45 min backward – no physics • Average over DFI period • Applicable for diabatic application, nudging to radar obs during DFI ‘pre-forecast’ Noise in surface pres at 1h forecast is much lower with DFI

  7. Rapid Update Cycle Model Vert CoordHybrid isentropic-sigma – 50 levels Stable clouds,NCAR mixed-phase (cloud Precipitationwater, rain water, snow, graupel, ice, ice particle number. concen. Sub-grid Grell-Devenyi ens scheme precipitation (144 members, closure/CIN Land-surfaceRUC LSM - 6-level soil/veg model, 2-layer snow model - Smirnova 9-12-hr fcst Current operational RUC: 13-km

  8. Recent changes to RUC13 3DVAR analysis • (among many): • 1. Use of surface obs throughout PBL(NCEP Fall 2004) • 2. Cloud analysis(GOES, METAR ceiling/vis/curr-wx)

  9. PBL-based METAR assimilation -- create additional obs corrections thru PBL Use METAR data through PBL depth from 1h fcst RUC oper analysis 18z 3 Apr 02 IAD Effect of PBL-based METAR assimilation x x x x

  10. CAPE impact from two RUC enhancements 0000 UTC 21 Apr 2004 3h fcst WITH enhancements 3h fcst OPERATIONAL • RUC enhancements: • Use of METAR obs through • boundary-layer depth(Sept 04) • Assimilation of GPS precipitable • water observations(RUC13 - ~Jun05) Tornadoes Severe reports NWS SPC Norman, OK

  11. RUC Cloud Analysis • Use GOES CTP, radar reflectivity, lightning, • METAR (clouds,wx,vis) to modify 1h fcst 3-d q* fields • Clear/build (change qc, qi, qv) with logical arrays • Safeguards for pressure-level assignment problems • (marine stratus, convective clouds) • Use nationwide mosaic radar data to modify water • vapor, hydrometeor fields – in testing, crude • Lightning data used as a proxy for radar reflectivity • Feedback to cumulus parameterization scheme – bypass convective inhibition via radar/lightning, GOES ECA

  12. 100 200 300 400 500 600 700 800 900 999 PRES dBZ Qi Qs Qr Rainwater, snow,cloud ice and reflectivity before ( ) and after (----) GOES radar/lightning adjustment GOES cloud top pressure Radar/lightning data 100 200 300 400 500 600 700 800 900 999 PRES RH Qv Qc Cloudwater, water vapor and relative humidity before ( ) and after (----) GOES Cloud- top pressure adjustment

  13. LIFR IFR MVFR VFR CLR Sample ceiling analysis impact Analysis WITH cld/wx/ vis obs Ceiling from RUC hydrometeors Observations 1800 UTC 17 Nov 2003 Aviation Flight Rules Analysis NO cld/wx/ vis obs cloud ceiling height (meters)

  14. Experimental or future RUC Obs Sources To be added in next 6 months to experimental 13km RUC

  15. Radar reflectivity assimilation - experimental RUC13 init 09z - 3-6h precip Valid 12-15 UTC 6 Sept 2005 Control – oper RUC Obs – 1345 UTC Exp RUC13 W/ rad ref assim

  16. Sample 3DVAR analysis with radial velocity 0800 UTC 10 Nov 2004 Cint = 2 m/s Dodge City, KS * * Analysis WITH radial velocity * * * K = 15 wind Vectors and speed * Cint = 1 m/s Amarillo, TX Vr Dodge City, KS * Analysis difference (WITH radial velocity minus without) * * Vr 500 mb Height/Vorticity Amarillo, TX

  17. Planned Rapid Refresh domain • Rapid Refresh • replace RUC – 2007-08 • 13km resolution • use WRF model Current RUC CONUS domain • Goals: • Hourly NWP • update in • - Alaska • Wider E. Pacific • - Canada • - Caribbean Sea

  18. The RUC by 2008, testing in 2006 • “Rapid Refresh” • Simple  more complex assimilation of radar reflectivity and radial winds • Improved use of sat data, GPS, aircraft, surface/mesonet • Use of WRF model w/ RUC-like physics • Use of NCEP data assimilation (GSI) with RUC-specific enhancements – use of sfc data, cloud analysis • North American coverage

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