High-resolution WRF runs for NACP

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