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High-Resolution WRF Runs for NACP: October 2008 Update by Thomas Nehrkorn

This update provides an overview of high-resolution Weather Research and Forecasting (WRF) model outputs generated at NASA's Columbia supercomputer facility, funded by NASA and NOAA. It details the verification procedures and sample verification results for WRF runs from 2004 to 2007, using a multi-domain setup with various resolutions. The document discusses the effects of nudging on wind and PBL height accuracy, and outlines future plans for model upgrades and uncertainty characterization.

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High-Resolution WRF Runs for NACP: October 2008 Update by Thomas Nehrkorn

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  1. High-resolution WRF runs for NACP October 2008 An update provided by Thomas Nehrkorn Atmospheric & Environmental Research, Inc. 131 Hartwell Ave Lexington, Massachusetts 02421 www.aer.com

  2. Introduction • Provide overview of available WRF fields • Generated at NASA Columbia supercomputer facility • Funding provided by NASA and NOAA • Provide overview of verification procedure and sample verification results • Discuss future plans

  3. Overview of Time periods and Domains • 2004 and 2006: • 5-domain setup: 40km, 10km, 3@2km resolution • 2005: • 2-domain setup: 40km and 10km • 2007: • 2-domain setup: 40km and 10km (extended further west)

  4. WRF domains used for 2004 and 2006 • 40km: 207x192 • 10km: 349x357 (encloses d03-d05) • 2km: 251x251 (Moody, WLEF, and Argyle)

  5. WRF domains used for 2005 • 40km: 207x192 • 10km: 393x357 (extended W for OK/CO sites)

  6. WRF domains used for 2007 • 40km: 207x192 • 10km: 521x357 (extended W to CA)

  7. WRF runs setup • Using WRF v2.2 • Customized to provide: • Time-averaged mass-coupled winds, convective fluxes • NARR input used for I.C. and B.C. • 30-hr Forecasts, initialized every 24 hr (00 UTC) • Use hours 7-30 from each forecast (avoid spin-up) • Outer domain uses analysis nudging to NARR • Inner domains use 1-way nesting • Hourly output • Netcdf (WRF native format), all fields archived • ARL (compressed, STILT-compatible)

  8. WRF runs verification • Winds: using WRF/STILT to colocate: • WRF winds as determined from short-term trajectory computation • Raob winds at selected pressure levels • 925, 850, 700, 500, 400, 300 hPa • PBL heights: • Profilers: TEXAQS (2006) and ICARTT (2004) • Raobs: derived from T,q,u,v • using WRF/STILT to colocate: • PBL heights computed by STILT from WRF T,q,u,v • PBL heights computed by WRF

  9. Raob winds results: effects of nudging • For May-Aug 2004, compare: • WRF v2.2 fields with nudging (case06, 40km) • WRF v2.1.2 fields without nudging (case09, 40km) • Fields generated during earlier work for Argyle tower simulations • Result show effectiveness of nudging in limiting error growth

  10. Raob winds results: outer / inner domains • Results shown for June-July-August 2004: • d01 and d02 compared against identical Raobs

  11. Raob winds results: outer / inner domains • Results shown for June-July-August 2004: • d03-d05 have 1-3 Raobs inside domain

  12. Raob winds results: outer / inner domains • Wind errors generally larger in nested domains • Nudging only through B.C. from outer domain • Smaller scales get penalized by point statistics • Error growth from 12-24 hours evident (viz. jja_d04 in previous slide), but not uniformly at all seasons/domains/levels • Colocations have been performed for all domains, and all years: • 2004 and 2006: subsampled forecasts (~1/3) • 2005 and 2007: all forecasts

  13. PBL height verification • Ongoing. Preliminary results: • WRF/STILT PBL heights tend to be overestimates • Errors are comparable for d01, d02, and d03

  14. PBL height verification • Sample time series of simulated/observed: • Simulated values only shown for hours with obs

  15. Future Plans • Characterization of uncertainties • Characterize transport uncertainties based on Raob wind-colocation error statistics • Characterize PBL height bias and random errors • Extend PBL height verification: • Extend to ICARTT 2004 profiler data • Cross-compare against Raob-derived PBL heights • Extend WRF runs to additional time periods • Use existing setup

  16. Future Plans - continued • Pending NSF project: • Upgrade to WRF v3, explore different physics options, evaluate impact on WRF fields • Outstanding issue: Handling of nested domains in STILT • A single particle exiting inner-most domain causes switching to coarser domain for all particles • We will evaluate the feasibility of importing relevant upgrades from HYSPLIT to STILT

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