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Model Set-up and Nesting Approach

Model Set-up and Nesting Approach. Cindy Bruyère. NCAR Earth System Laboratory National Center for Atmospheric Research. NCAR is Sponsored by NSF and this work is partially supported by the Willis Research Network and the Research Program to Secure Energy for America.

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Model Set-up and Nesting Approach

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  1. Model Set-up and Nesting Approach Cindy Bruyère NCAR Earth System Laboratory National Center for Atmospheric Research NCAR is Sponsored by NSF and this work is partially supported by the Willis Research Network and the Research Program to Secure Energy for America Bruyere Model Setup RPSEA 0310

  2. Phase 1: Tropical Channel Two-way nested domain 12 km Over NA Basin Bruyere Model Setup RPSEA 0310

  3. Tropical Channel: Results Bruyere Model Setup RPSEA 0310

  4. CCSM ~ 150 km Image by Steve Dayo @UCAR WRF 12 km WRF 36 km CCSM ~ 150 km Nested Regional Climate Model Setup Bruyere Model Setup RPSEA 0310

  5. Nested Regional Climate Model Setup • CCSM3: • One Current Climate member (1950-1999) • 3 ensemble members from 2000-2060 under two A2 and one A1B scenarios (IPCC-AR4) • NRCM: • 1 ensemble member from 1995-2005, 2020-2030 and 2045-2055 under A2 scenario at 36 km (complete), and 12 km grid spacing (in progress) • No nudging • Statistical downscaling of CCSM3 to fill in intermediate periods Bruyere Model Setup RPSEA 0310

  6. Track density of model tropical and extratropical storms Jan-Dec 1995 Regional Model: Results Cat 3 HurricaneOctober 2046 Bruyere Model Setup RPSEA 0310

  7. NCEP/NCAR Reanalysis Channel NRCM Shear in the Model (avg Aug-Oct) Bruyere Model Setup RPSEA 0310

  8. NCEP/NCAR Reanalysis CCSM Similar Bias in CCSM Bruyere Model Setup RPSEA 0310

  9. Possible Causes of High Shear • CCSM exhibits same bias • High shear is due to strong Westerly flow at 200mb • Entire tropics has warm bias at upper-levels in CCSM, inducing westerly wind anomaly • Also an El Niño-like SST anomaly → alters Walker Circulation → contributes to westerly wind anomaly Bruyere Model Setup RPSEA 0310

  10. NCEP/NCAR Reanalysis NRCM + channel configuration NRCM Sensitivity Studies NRCM + Reynolds SST Bruyere Model Setup RPSEA 0310

  11. Bias Correction • Describe 6-hourly CCSM data for entire simulation (1950-2060) as an average annual cycle plus a perturbation term: • CCSM =CCSM + CCSM’ (1) • - using a 20-year averaging period (1975-1994), • - applied to variables: U,V,Z,T,RH,Surface T and PMSL • Do the same for NCEP-NCAR Reanalysis data: • NNRP = NNRP + NNRP’ (2) • Replace CCSMwithNNRP: • CCSMc = NNRP + CCSM’ (3) • Base climate provided by NCEP-NCAR Reanalysis data and the weather and climate change signal provided by CCSM 11 Bruyere Model Setup RPSEA 0310

  12. NCEP/NCAR Reanalysis NRCM Adjusted N. A. Regional Climate Shear after Adjustment Bruyere Model Setup RPSEA 0310

  13. Regional Model: New Results Bruyere Model Setup RPSEA 0310

  14. Conclusions • Tropical Channel runs developed storms in the MDR, although fewer than observed • Running NRCM directly forced with CCSM output resulted in no storms in MDR • Strong bias in shear and SST linked with this result • Bias corrected CCSM allowed development of storms in MDR • Next stage is the completion of the 12km runs Bruyere Model Setup RPSEA 0310

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