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Operational Use of the Rapid Update Cycle

Operational Use of the Rapid Update Cycle

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Operational Use of the Rapid Update Cycle

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  1. Operational Use of the Rapid Update Cycle Stan Benjamin - NOAA/FSL benjamin@fsl.noaa.gov http://maps.fsl.noaa.gov - RUC web page COMAP Symposium 99-1 20 May 1999

  2. What Runs Where • Rapid Update Cycle (RUC) • Operational Version at NCEP • Mesoscale Analysis and Prediction System (MAPS) • Experimental Version at NOAA/ERL/FSL (Essentially the same software. New capabilities tested first in MAPS at FSL)

  3. RUC/MAPS Purpose • Provide high-frequency mesoscale analyses and short-range forecasts for: • aviation • severe weather forecasting • forecasts for public • other transportation • agriculture

  4. The 1-h Version of the RUC Data cutoff - +20 min, 2nd run at +55 min at 0000, 1200 UTC

  5. NCEP Operational Models

  6. Key Personnel -- RUC-2 Development/Implementation Stan Benjamin Analysis/model dev, mgmt John Brown Model dev, parameterizations Kevin Brundage NCEP impl., WWW, graphics Dezso Devenyi 3-d VAR development Georg Grell Model dev., parameterizations Barry Schwartz Obs ingest, obs sensitivity studies Tanya Smirnova Land-sfc processes Tracy Lorraine Smith Obs ingest, obs sensitivity studies Tom Schlatter Interaction w/ NCEP Geoff Manikin NCEP liaison for RUC, impl. Geoff DiMego Interaction w/ NCEP/NCO, NWS

  7. Uses of the RUC • Explicit Use of Short-Range Forecasts • Aviation Weather Center - airmets, sigmets • Storm Prediction Center - severe weather watches • FAA • Dept. of Transportation - air traffic management • National Weather Service Forecast Offices • Airline Forecasting Offices • NASA Space Flight Centers • Monitoring Current Conditions with Hourly Analyses • Evaluating Trends of Longer-Range Models

  8. RUC1 vs RUC2 Characteristics

  9. RUC-1 versus RUC-2, cont.

  10. Hourly Data for 40 km MAPS/RUC-2 ** **not used since 1/99 pending QC issues Yellow items new for RUC-2

  11. Hourly Data for 40 km MAPS/RUC-2, cont. Yellow items new for RUC-2 Real-time observation counts at http://maps.fsl.noaa.gov for RUC-2 and 40-km MAPS

  12. Advantages of q Coords for Data Assimilation Analysis - adaptive 3-d correlation structures and analysis increments, esp. nearbaroclinic zones - improved coherence of obs near fronts for QC Forecast Model - reduced vertical flux thru coordinate surfaces, leading to reduced vertical dispersion -- much of vertical motion implicit in 2-d horiz. Advection - conservation of potential vorticity - reduced spin-up problems (Johnson et al. 93 MWR)

  13. RUC-2 Time Availability vs. RUC-1 Improvements due to the 1-hr cycle and earlier data cut-off time

  14. RUC-2 Analysis • QC - buddy check, removal of VADs w/ possible bird contamination problems • 3-part analysis (all using optimal interpolation) 1) univariate precipitable water (PW) analysis - using satellite PW obs - update mixing ratio field 2) z/u/v 3-d multivariate analysis - update v based on height/thickness analysis increment, update psfc from height increment at sfc, update u/v at all levels

  15. RUC-2 Analysis, cont. 3) univariate analysis of condensation pressure at all levels, v at all levels. Also update u/v near sfc and psfc with univariate analysis with smaller correlation lengths • Update soil temp at top 2 levels to maintain (Tskin - T1-atmos) • Pass through soil moisture, cloud mixing ratios, snow cover/temperature (will alter these fields at future time)

  16. RUC-2 Analysis, cont. • Vertical spreading (correlation of forecast error) based on potential temperature separation (not pressure separation as w/ other models) • Analysis in generalized vertical coordinate (code applicable to pressure, sigma, or eta analysis) except for adjustment at end to reference potential temperatures and new psfc • Background is usually previous 1 hr RUC forecast

  17. Raob sounding RUC2 sounding Close fit to observations in RUC2 analysis

  18. Raob RUC after fix RUC before fix 7 April 99 significant-level fix in RUC-2

  19. RUCS 60 km Hourly Surface Analyses • Draws fairly closely to data • Persistence background field (1 hr previous analysis • some QC problems • no consistency with terrain • MAPS sea-level pressure, (Benjamin & Miller, 1990 MWR) • Blending to data-void region from NGM

  20. Surface Analyses/Forecasts in RUC-2 • integrated with 3-d 40 km 1 hr cycle • dynamic consistency with model forecast => accounts for: • land/water, mtn circulations, sea/lake breezes, snow cover, vegetation… • improved quality control - model forecast background prevents runaway bullseyes • forecasts out to 12 hr in addition to hourly analyses

  21. Surface Analyses/Forecasts in RUC-2, cont. • Same fields as in 60 km RUCS, plus all fields available in 3-d system RUC-2 sfc files (GRIB) 0.3 MB / output time all variables from RUCS plus precip precip type stability indices

  22. RUC-2 use of surface data All winds, sfc pressure obs used T/Td used if abs (Pstation - Pmodel) < 70 mb - about 90% west of 105ºW, 99% east of 105ºW |pmodel - pstn| ** w/I 5 mb of closest fit

  23. RUC-2 Model • Prognostic variables • Dynamic - (Bleck and Benjamin, 93 MWR) • v, p between levels, u, v • Moisture - (MM5 cloud microphysics) • q v, qc, qr, qi, qs, qg, Ni (no. conc. ice particles) • Turbulence - (Burk-Thompson, US Navy, 89 JAS) • Soil - temperature, moisture - 6 levels (down to 3 m) • Snow - water equivalent depth, temperature (soil/snow/veg model - Smirnova et al., 1997 MWR)

  24. RUC-2 Model, cont. • Numerics • Continuity equation • flux-corrected transport (positive definite) • Advection of v, all q (moisture) variables • Smolarkiewicz (1984) positive definite scheme • Horizontal grid • Arakawa C • Vertical grid • Non-staggered, generalized vertical coordinate currently set as isentropic-sigma hybrid

  25. RUC-2 Model, cont. • Cumulus parameterization • Grell (Mon.Wea.Rev., 1993) • simplified (1-cloud) Arakawa-Schubert • includes effects of downdrafts • Digital filter initialization (Lynch and Huang, 93 MWR) • +/- 40 min adiabatic run before each forecast

  26. MM5 Level 4 Microphysics • Predicts mixing ratios of water vapor, cloud water, rain water, cloud ice, snow, graupel and number concentration of cloud ice • Ongoing improvements in collaboration with NCAR/RAP • Continuous cycling of liquid and solid hydrometeors • NCEP C-90 CPU usage (12 hr forecast): • 10% microphysics • 15% advection of hydrometeors

  27. Montreal ice storm - 9h RUC2 forecast valid 2100 9 Jan 98. N-S cross sections of RUC2 microphysics | YUL

  28. RUC Land-surface Process Parameterization (Smirnova et al. 1997, MWR) Ongoing cycle of soil moisture, soil temp, snow cover/depth/temp)

  29. Fields From Soil/Snow Model • Soil temperature at 6 levels • Soil moisture at 6 levels • Surface runoff • Sub-surface runoff • Direct evaporation from bare soil • Evapotranspiration • Evaporation of canopy water • Condensation of water • Canopy water • Water dripping from the canopy

  30. Fields From Soil/Snow Model, cont. • Snow depth • Snow temperature • Accumulation of snow • Amount of melted snow • Flux of snow phase change heat • Predicted soil variables cycled since April 1996 • Predicted snow variables cycled since March 1997

  31. RUC - 2 Output Files • Isobaric main (25 mb, 212 grid) • 6 3-d variables (ht, temp, RH, u/v, vv) • 80 2-d variables (prec, indices, spec. level, …) • ~7 MB / output time • Surface fields (212 grid) • 25 2-d variables (p, T, TD, u/v, 3-h dp, precip, indices…) • ~0.3 MB / output time

  32. RUC - 2 Output Files, cont. • 211 isobaric/sfc grids (will add vert. Vel.) • BUFR hourly soundings - same format as Eta • ~290 stations • ~1.5 MB for 12-h fcst, all stations (week of 12/8/97) • Native - • ~10 MB / output time

  33. 40 km MAPS versus 32 km Eta Apr-Jul 1998

  34. 40 km MAPS versus 32 km Eta, cont.

  35. RUC vs. Eta - 12h fcsts - 7 April - 10 May 1999

  36. Improvements in 40-km RUC-2over RUC-1 • Wind analyses/forecasts - improved skill at all times • Temperature - improved skill, much reduced bias • RH - improved skill, much reduced bias • Turbulence - • sharp, coherent structures near frontal zones

  37. Improvements in 40-km RUC-2 • Icing - • explicit microphysics with cloud water/rain/snow/ice/graupel • Surface forecasts - • substantial improvement from addition of surface physics (multi-level soil/vegetation model, snow physics), clouds, improved radiation • Precipitation - • much better especially in orographic precip and heavy precip events

  38. Directions for Future RUC-2 Improvements(suggested by precipitation verification) • Improve cloud/moisture analysis. • Use of advanced microphysics in RUC-2 means that initial cloud errors can lead to underforecasting. Work is underway to add satellite, radar and surface data to forecast cloud fields. • Introduce fractional cloudiness into the model • Allow supersaturation at <100% RH within 40 km grid boxes • Convective parameterization (Grell, includes effect of downdrafts) • Gives reasonable performance but still needs tuning/improvement

  39. Dec 98 change bundle for RUC-2 • Y2K fixes • Analysis changes • smaller horiz. error correlation near sfc for T/Td, slightly less dependence on stability => improved sfc T/Td fit in mtns • fix to use of cloud drift winds => will have much more effect (over water only) • better fit to sfc obs • Model changes • fixes to sfc physics - reduction of cool bias in daytime • fixes to radiation - more cooling at night, slightly more heating in daytime • less convective precip over warm water

  40. Dec 98 change bundle for RUC-2, cont. • Diagnostic fixes • CAPE/CIN - mix lowest 30-40 mb - less jumpiness from analysis to 1h fcst • tropopause level fix • GRIB table fixes • Allow soil cycling with adequate precision • Boundary condition fix to account for Eta change in RH as of 11/3/98

  41. Apr 99 emergency change for RUC2 • Correctly uses raob sig-level temp/dewpoint data now. • Previously, missed sig-level T/Td data (TTBB) and forced in linearly interpolated structures between mandatory levels. • Significant improvement in RUC grid sounding structures and in overall RUC performance

  42. May 99 post-proc fixes for RUC2 • Bug/consistency fixes for diagnosis of sfc T/Td in RUC2. (fix to lapse rate range) • Biases in west US for T/Td reduced, 2 °C  0 • s.d. temps over US from 2.0  1.4 °C • (verification against METAR obs) • CAPE- searches lowest 300 mb, not 180 mb • More smoothing of isobaric winds in lower troposphere, near tropopause • Use of NESDIS ice field • Much faster running of RUC - 10 procs for all runs

  43. RUC-2 Weaknesses • Still some precip spin-up problem, despite cycling of cloud/precip variables, esp. for light precip/overrunning (1-3 hr late) • Fix: Add cloud analysis - 1999 - 1st version, allow for cloud at RH < 100% • Too much precip over warm oceans, too little near SE coast in cold season • Dec 98 fix package helped some - work underway on fixing tendencies input to Grell convective parameterization • Daytime convective precip in summer too widespread • Upcoming fix on tendencies input to Grell scheme

  44. RUC-2 Weaknesses, cont. • Convective precip forecasts miss many small areas, underforecast peak amounts. • Lower equitable threat score than Eta • more detailed than Eta • Too much graupel near 0ºC • Fix: with 20-km RUC, collaboration with FSL and NCAR on microphysics fixes • Diurnal cycle of surface temperature a little too weak • a little too warm at night • Dec 98 fix package - sfc flux change, radiation fix, GRIB precision to allow proper soil moisture cycling • May 99 fix - improve diagnosis of sfc temp/Td diagnosis -- significant reduction in bias

  45. RUC-2 Weaknesses, cont. • Detailed (noisy?) output compared to other models, especially vertical velocity • Detail is probably realistic over terrain • Analysis near coastlines • does not account for land/sea contrast • analysis increments over coast extrapolated over sea Fix: Account for lower horizontal correlation in analysis when crossing coastline

  46. Fixed RUC-2 Weaknesses • Analysis sounding structure • irregular near ground if only sfc data assimilated Fix: analysis tuning (Dec 98) Fix: sig-level bug fix (Apr 99) ***************** • CAPE/CIN • analysis values previously too high in high CAPE areas • jump between analysis and 1-h forecasts Fix: CAPE software (Dec 98) (May 99 - parcel search now in lowest 300 mb, not 180 mb layer)

  47. RUC-2 Strengths • Surface fields, esp. surface winds • sfc files • analysis and forecast • small • standard sfc fields plus precip, stability, precip type • Topographically induced circulations • sea/lake breezes (scale too large but they’re there) • mtn/valley circulations • differential friction effects