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M. Tsidulko, J. Mcqueen, P. Lee, Y. Tang, H. Huang, E. Rogers, G. Dimego, M. Ek NOAA/NCEP/EMC

Changes to the Operational NCEP North American Model (NAM) and impacts on key meteorological fields for Air Quality. M. Tsidulko, J. Mcqueen, P. Lee, Y. Tang, H. Huang, E. Rogers, G. Dimego, M. Ek NOAA/NCEP/EMC 2008 National Air Quality Conferences April 8, 2008 Portland OR. CONUS.

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M. Tsidulko, J. Mcqueen, P. Lee, Y. Tang, H. Huang, E. Rogers, G. Dimego, M. Ek NOAA/NCEP/EMC

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  1. Changes to the Operational NCEP North American Model (NAM) and impacts on key meteorological fields for Air Quality M. Tsidulko, J. Mcqueen, P. Lee, Y. Tang, H. Huang, E. Rogers, G. Dimego, M. Ek NOAA/NCEP/EMC 2008 National Air Quality Conferences April 8, 2008 Portland OR

  2. CONUS 8-Hr Max BIAS May 1 Sep 8 CMAQ and NAM Changes Summer 2007 2008 NAM upgrade Retrospective AQF tests 2008 CMAQ upgrade

  3. North American Mesoscale (NAM) Analysis and Forecast System upgrade (operational since March 30, 2008) • Expanded computational domain by 18% • Gravity Wave Drag / Mountain Blocking low-level flow is blocked below a dividing streamline (air flows around, not over barrier) changes winds aloft (momentum deposition) • Unified (with NCAR) land-surface physics uses total soil moisture rather than liquid soil moisture to determine bare-soil evaporation, which results in greater moisture fluxes (and thus higher near-surface dew point temperatures) over regions of frozen, bare soil with patchy or no snow cover • Improved computation of surface longwave radiation remove averaging of tendencies from two lowest layers upward LW at sfc computed based on skin temp instead of average of skin T and lowest model layer T • Bug fix for climatological values of stratospheric O3 stratospheric ozone fix in the computation of latitude: the error led to using climatological ozone values valid at the equator at all latitudes • Modified passive advection relax requirement for exact conservation of q, TKE, cloud water in advection step due to open inflow/outflow at the lateral boundary

  4. North American Mesoscale (NAM) Analysis and Forecast System upgrade (operational since March 30, 2008) (continued) • New (August 2007) version of GSI code • Retuned background errors (gives improved obs fit to first guess) • Assimilation of new/better observation types • AIRS radiances, MODIS wind, Mesonet wind observations, Single field-of-view GOES radiances In this presentation – different names for the same models 2007 Operational NAM: NAM Ops NAM Upgraded NAM: NAM-Y NAME NAMEXP Parallel NAM NEW NAM

  5. Example of impact of GWD on lower tropospheric vertical profiles : Obs=black, Ops NAM=Red, New NAM=blue

  6. NAM vs NAM-Y 2 m Temperature Errors (C)CONUS 12 Z CycleAug. 2007 Retros 48h Forecast (Valid 12 Z) 36h Forecast (Valid 00 Z) NAM-Y has stronger diurnal cycle: Warmer in day, cooler at night

  7. NAM vs NAM-Y Temperature Errors (C)Aug. 2007 Retros 48h Forecast (Valid 12 Z) 36h Forecast (Valid 00 Z) East U.S. : NAM-Y warm bias at 850 mb West U.S.: NAM-Y warm bias at 850, 700 mb

  8. 2-m temperature Aug07 west east ≈ops, day: +1C vs OBS ≈ops, day/night: +1C vs OBS

  9. 2-m RH Aug07 west east day: <ops, -5% vs OBS night: <ops, -4% vs OBS day: <ops, -5% vs OBS night: ≈ops, ≈OBS

  10. 10-m wind2 Aug07 west east day/night: ≈ops, ≈OBS day/night: ≈ops, ≈1m/s>OBS generally ≈ operational NAM 2-m temps & RH vs OBS: east/west slightly warmer/drier 10-m winds vs OBS: east slightly high bias, west similar

  11. 14-20 Aug 2007 8-Hr Max Ozone Verification (mean bias) NE Aug 4 Aug 20 PC LM Aug 4 Aug 20 Aug 4 Aug 20 R. Mathur, EPA

  12. Verification Sub-domains SW Coast includes both LA, SD & SJV

  13. NAM-Y vs NAM 2m Temperature errors SW Coast and GMC sub-regions (12z cycle) SWC GMC SWC 48h Forecast (Valid 12 Z) 36h Forecast (Valid 00 Z) • Night: • NAM-Y Temperature warm bias improved over GMC/SWC • DAY: • NAM-Y Temperature improved for SWC • Overpredicted for GMC

  14. NAMy NAM higher predicted O3 along the coast in NAMy R. Mathur, EPA

  15. Aug 15, 2007 00Z (36 h forecast) NAM NAM-Y Houston area: NAM-Y slightly warmer; slightly lower winds (less clouds, more radiation) ahead of Erin (Aug.14/15)

  16. NAMy NAM Systematic over-estimation of O3 downwind of LA basin reduced with NAMy R. Mathur, EPA

  17. Aug 15, 2007 00Z (36 h forecast) NAM NAM-Y Slightly higher PBL in NAM-Y

  18. NAM-Y vs NAM Temperature errors NE and SE U.S. sub-regions (12z cycle) NEC 36h Forecast (Valid 00 Z) 36h Forecast (Valid 00 Z) • Temperature: • NEC: Warm Bias as front approached • SEC : slightly warmer esp. 10-12th • RH: • NEC: dry bias esp. 11th-17th

  19. NAMy NAM Higher ozone in NAM-Y

  20. August 15, 2007

  21. Delayed front in NAM-Y

  22. Ozone, Aerosol and PBL Verification System at NCEP Observations Model output RAOB TKE PBL NAM Mix Layer Ht Aircraft PBL calculation PBL height Ri PBL/no fluxes Profiler Ri PBL/fluxes Aerosol PM2.5 AIRNOW CMAQ Ozone Ozone Forecast Verification System Statistics

  23. PBL Verification: August 2007 retro runs Verification time: 00z 12 hrs forecast 36 hrs forecast Eastern US Para TKE PBL ~ 200-300m higher than Ops TKE PBL(12fhr); ~50-250m(36fhr) Both TKE PBLs higher than Observations Almost no change in Ri PBL Acm2 PBL ~50m higher than Ri PBL and fits the Obs best

  24. PBL Verification: August 2007 retro runs Verification time: 00z 12 hrs forecast 36 hrs forecast Western US TKE PBL better fits Obs PBL Aug 7-12; Acm2 PBL better for Aug 13-18 Smaller changes in TKE PBLs; generally higher than Obs but sometimes lower Small changes in Ri PBL Acm2 PBL ~100-200m higher than Ri PBL

  25. Summary • Ozone impact largest in California & Gulf Mexico • NAM-Y improves warm temperature, RH biases esp. in Day for SWC. Minor changes elsewhere. • NAM-Y increases RH dry bias over GMC • NAM-Y increases low speed bias over GMC • NAM-Y increases PBL (from TKE scheme) high bias in the Eastern US • Resulted in slightly increased ozone over-prediction bias overall (2-4 ppb) • Large impacts locally (5-10 ppb) by delaying frontal and storm timing

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