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Improvements to Surface Flux Computations in the MRF PBL Scheme, and Refinements to Urban Processes in the Noah LSM Model With the NCAR/ATEC Real-time FDDA and Forecast System Yubao Liu, Fei Chen, Tom Warner and Scott Swerdlin Research Applications Laboratory

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  1. Improvements to Surface Flux Computations in the MRF PBL Scheme, and Refinements to Urban Processes in the Noah LSM Model With the NCAR/ATEC Real-time FDDA and Forecast System Yubao Liu, Fei Chen, Tom Warner and Scott Swerdlin Research Applications Laboratory National Center for Atmospheric Research

  2. Outline • MM5-based RTFDDA • A common problem in the MM5 PBL schemes • Modifications to the MRF PBL scheme • Refinements to the Noah LSM-urban • Results • Summary

  3. Wind Prof ACARS GOES All WMO/GTS Radars t FDDA Forecast MESONETs TAMDAR Etc. Real-Time FDDA and Forecasting (RTFDDA) System New 12 - 48 h forecast every 1 - 12 hrs, using all obs up to “now” obs WRF/MM5-FDDA Multi-scale DA and FCST Cold start

  4. Military operations • Army test ranges • Homeland security • Wyoming cloud seeding • FAA aviation weather • 2002-SLC Olympics • 2004-Athens Olympics • 2006-Torino Olympics • Joint Urban 2003, OKC • Colorado wild fire • Kauai island effect • New York City • 2005 Hurricanes • TAMDAR appli. • … 12 Regular Operational RTFDDA Systems 20+ Special Operation Sites NCAR RTFDDA Applications

  5. Continuing RTFDDA Modeling R&D: • Incorporate more new observations • Enhance data quality control • Refine data assimilation algorithms • Improve model physics schemes • Next-gen: ensemble DA and probabilistic forecasting: E-RTFDDA – (this afternoon)

  6. Vsfc from six PBL schemes August 2002, 5 ranges, d3/d4 OBS MRF PBL (MM5-RTFDDA operations) (Zhang and Zheng, 2003) Modifications to the MRF PBL Physics • Known problems with MM5 PBL schemes Underestimates day-time surface winds Overestimates PBL heights

  7. ziRi < Ric ? … … … 3 3 Rib Ribl 2 2 Rib Ribl a 1 1 g Rib Ribl Modifications to the MRF PBL Physics More realistic computation of thermally induced turbulence Alternative definition of PBL height by using local Ri More accurate surface heat-exchange formulation

  8. RTFDDA Exp. Comparison of Zi, simulated by the old and new PBL schemes with the ANL profiler measurement at Oxford, KS. OLD New Modifications to the MRF PBL Physics • Results (Case: May 27 – 28, 2003) Significant improve PBL developments and evolutions

  9. Modifications to the MRF PBL Physics • Results (Case: May 27 – 28, 2003) Correct day-time surface (10-m) wind biases RMSE (m/s) BIAS (m/s) OLD f1012 NEW f1012 NEW final OLD Final GMT (hour)

  10. Modifications to the MRF PBL Physics • Statistical Results 2002 (w/o mods) vs 2003 (with mods) RTFDDA operations over the Northeastern States

  11. Refinements to Noah LSM Urban Physics Effects of urban canopy on PBL and airflow Solar radiation Intense shear at the top Drag Sunlit Heat trapped Wake Mixing Shadow Urban surface: Dry, more-frictional and heat-trapped

  12. Refinements to Noah LSM Urban Physics • Modify the Noah-LSM urban physics parameters for urban bulk effect • Larger roughness length • turbulence generated by roughness elements • drag due to buildings • Smaller albedo • radiation trapping • Larger thermal capacity and conductivity • heat storage in substrate • Smaller water capacity

  13. RTFDDA Operation DuringJU2003 (OKC) Five 2-way-nested Domains (45/15/4.5/1.5/0.5 km) D1 D2 D3,4,5

  14. Land use and water bodies on Domain 4 defined with USGS+MODIS data RTFDDA Operation DuringJU2003 (OKC) Aerial picture Domain 4, DX = 1.5 km

  15. Average of eight clear-sky days in July 2003, at 06Z RTFDDA Operation DuringJU2003 (OKC) 2-m temperature and 10-m wind vectors Surface sensible heat flux ( W/m2 )

  16. PBL Height (m) Wind Speed (m/s; LLJ) B H(km) A URBAN B A 10 km Case examples – Nocturnal PBL – 06Z June 24, 2003 RTFDDA Operation DuringJU2003 (OKC)

  17. A B 37.0 URBAN Case examples – Day-time PBL – 18Z July 5, 2003 RTFDDA Operation DuringJU2003 (OKC) PBL Height ( m ) W ( m / s ) H(km) A B 10 km

  18. JU2003: Mixing Layer Height Forecasts on Eight Good Weather Cases Color shade: Low-Power S/N ratio measurement from the ARL wind profilerRed and blue lines: RTFDDA forecast of Mixing Layer height at two OKC sites

  19. Comparison of Surface Temperature Diurnal Evolutions S P M Urban Suburban Rural JU2003: Cases July 16 and July 24

  20. Summary and Conclusions • The surface flux and mixing-layer height computations in the widely-used MRF PBL scheme were modified. • Simulation results show significant improvements in surface winds, and other variables as well. • The Noah-LSM urban processes were refined to account for the basic properties of the urban canopy. • Model results show encouraging simulations of urban heat-island, urban-induced meso-g scale circulations, and PBL development. • Both mods have been incorporated into community MM5 and WRF models. • This work suggests  many research opportunities for mesoscale modeling, and  large improvements from even simple scheme “tune-up”

  21. 37.0 A B URBAN URBAN JU2003 (OKC) RTFDDA URBAN SIMULATIONCase examples – Day-time PBL – 18Z July 5, 2003 Q ( K ) Qe (K) H(km) 37.0 A B A B 10 km

  22. T 2 ( C ) W ( m/s ) at p = 850 hPa 37.0 Tm=35.5C To=35C Case examples – Day-time PBL – 18Z July 5, 2003 RTFDDA Operation DuringJU2003 (OKC)

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