1. The impact of mesoscale PBL parameterizations on the evolution of mixed-layer processes important for fire weather Joseph J. Charney USDA Forest Service, Northern Research Station, East Lansing, MI Daniel Keyser Department of Atmospheric and Environmental Sciences, University at Albany, Albany, NY

2. 1.Background 2.WRF model configuration 3.Double Trouble State Park (DTSP) wildfire case study 4.Summary and future work Organization

3. Mesoscale models are important tools for fire- weather forecasting and research applications. The surface-based mixed layer can profoundly influence fire–atmosphere interactions. Mixed-layer profiles of temperature, moisture, and wind strongly affect the evolution of a wildland fire. Mixed-layer processes are incorporated into mesoscale models through the planetary boundary layer (PBL) parameterization scheme. Background

4. WRF version 3.1 4 km nested grid 51 sigma levels, with 21 levels in the lowest 2000 m NARR data used for initial and boundary conditions Noah land-surface model RRTM radiation scheme MRF, YSU, MYJ, MYNN PBL schemes WRF model configuration

5. PBL schemes MRF (Hong and Pan 1996): MRF PBL; predecessor to YSU scheme with implicit treatment of entrainment layer. YSU (Hong et al. 2006): update of MRF scheme; explicit entrainment layer, reduced mixing in high wind regimes, more realistic diurnal PBL growth. MYJ (Janjić 1990, 1994): TKE-based PBL prediction scheme used in Eta and MM5 models; Mellor–Yamada level 2.5 turbulence closure and local vertical mixing. MYNN (Nakanishi and Niino 2004): update to the MYJ scheme; deeper mixed layer, better representation of vertical moisture gradients. WRF model configuration

6. Surface physics schemes MRF: MM5 similarity scheme YSU: MM5 similarity scheme MYJ: Eta similarity scheme MYNN: updated version of Eta similarity scheme WRF model configuration

7. Surface physics schemes Simulations with the MYNN PBL scheme were rerun using the surface physics schemes for the MRF, YSU, and MYJ PBL schemes. Changing the surface physics scheme results in relatively minor differences compared with the differences that arise from changing the PBL scheme. WRF model configuration

8. DTSP wildfire case study DTSP wildfire event Occurred on 2 June 2002 in east-central NJ An abandoned campfire grew into a major wildfire by 1800 UTC Burned 1,300 acres Forced closure of the Garden State Parkway Damaged or destroyed 36 homes and outbuildings Directly threatened over 200 homes Forced evacuation of 500 homes Caused ~$400,000 in property damage

9. DTSP wildfire event Fire location OKX upper air station KWRI surface station New Brunswick wind profiler

10. DTSP wildfire observations Observed skew T–log p sounding at Upton, NY (OKX), valid at 0000 UTC 3 June 2002

11. Simulated skew T–log p sounding at OKX valid at 0000 UTC 3 June 2002 MRF DTSP wildfire simulations WRF simulations initialized at 1200 UTC 1 June 2002

12. Simulated skew T–log p sounding at OKX valid at 0000 UTC 3 June 2002 YSU DTSP wildfire simulations

13. MYJ Simulated skew T–log p sounding at OKX valid at 0000 UTC 3 June 2002 DTSP wildfire simulations

14. MYNN Simulated skew T–log p sounding at OKX valid at 0000 UTC 3 June 2002 DTSP wildfire simulations

15. Wind profiler observations at New Brunswick, NJ, from 1100 UTC to 2100 UTC 2 June 2002 DTSP wildfire observations

16. MRF DTSP wildfire simulations Simulated skew T–log p sounding at the fire location valid at 1800 UTC 2 June 2002

17. YSU DTSP wildfire simulations Simulated skew T–log p sounding at the fire location valid at 1800 UTC 2 June 2002

18. MYJ DTSP wildfire simulations Simulated skew T–log p sounding at the fire location valid at 1800 UTC 2 June 2002

19. MYNN DTSP wildfire simulations Simulated skew T–log p sounding at the fire location valid at 1800 UTC 2 June 2002

20. DTSP wildfire simulations Time series at fire location valid from 1200 UTC to 2100 UTC 2 June 2002 of simulated surface temperature

21. DTSP wildfire simulations Time series at fire location valid from 1200 UTC to 2100 UTC 2 June 2002 of simulated surface mixing ratio

22. DTSP wildfire simulations Time series at fire location valid from 1200 UTC to 2100 UTC 2 June 2002 of simulated surface wind speed

23. DTSP wildfire simulations Vertical profiles at fire location valid from 1200 UTC to 2100 UTC 2 June 2002 of simulated temperature

24. DTSP wildfire simulations Vertical profiles at fire location valid from 1200 UTC to 2100 UTC 2 June 2002 of simulated temperature

25. DTSP wildfire simulations Vertical profiles at fire location valid from 1200 UTC to 2100 UTC 2 June 2002 of simulated temperature

26. DTSP wildfire simulations Vertical profiles at fire location valid from 1200 UTC to 2100 UTC 2 June 2002 of simulated temperature

27. DTSP wildfire simulations Vertical profiles at fire location valid from 1200 UTC to 2100 UTC 2 June 2002 of simulated mixing ratio

28. DTSP wildfire simulations Vertical profiles at fire location valid from 1200 UTC to 2100 UTC 2 June 2002 of simulated mixing ratio

29. DTSP wildfire simulations Vertical profiles at fire location valid from 1200 UTC to 2100 UTC 2 June 2002 of simulated mixing ratio

30. DTSP wildfire simulations Vertical profiles at fire location valid from 1200 UTC to 2100 UTC 2 June 2002 of simulated mixing ratio

31. DTSP wildfire simulations Vertical profiles at fire location valid from 1200 UTC to 2100 UTC 2 June 2002 of simulated wind speed

32. DTSP wildfire simulations Vertical profiles at fire location valid from 1200 UTC to 2100 UTC 2 June 2002 of simulated wind speed

33. DTSP wildfire simulations Vertical profiles at fire location valid from 1200 UTC to 2100 UTC 2 June 2002 of simulated wind speed

34. DTSP wildfire simulations Vertical profiles at fire location valid from 1200 UTC to 2100 UTC 2 June 2002 of simulated wind speed

35. An intercomparison of the MRF, YSU, MYJ, and MYNN PBL schemes in WRF version 3.1 for the DTSP wildfire event indicates that the behavior of these schemes is consistent with that documented in the literature. The MRF and YSU schemes produce less directional wind shear than the MYJ and MYNN schemes. The diurnal growth of the mixed layer is more gradual in the YSU, MYJ, and MYNN schemes than in the MRF scheme. The YSU and MYNN PBL schemes exhibit a deeper mixed layer than the MYJ scheme. Summary

36. Future work The methodology developed for the DTSP wildfire event will be extended to additional events. Candidates include the Warren Grove (NJ, 2007), Evans Road (NC, 2008), and Cottonville (WI, 2005) wildfires. Aspects to be examined for these events: 1) effects of the entrainment formulation on mixed-layer growth 2) sensitivity of mixing ratio profiles in the mixed layer to the choice of PBL scheme 3) performance of the PBL schemes in high-wind regimes