Mesoscale Numerical Weather Prediction over Antarctica: AMPS and Support for Ground-based Astronomy

1. Mesoscale Numerical Weather Prediction over Antarctica: AMPS and Support for Ground-based Astronomy Jordan G. Powers Mesoscale and Microscale Meteorology Division Earth and Sun Systems Laboratory National Center for Atmospheric Research Boulder, Colorado, USA  Antarctic NWP and AMPS  AMPS Capabilities and Application Issues  Summary

2. Antarctica and Topography • McMurdo Station Topography from NASA ICESat (Ice, Cloud, and Elevation Satellite)

3. I. Antarctic NWP and AMPS (Antarctic Mesoscale Prediction System) • Issues in Antarctic NWP: Forecasting for optical turbulence – What numerical models/forecast systems cover Antarctica? – What are the effective resolutions of the models? – Can the forecast output be obtained? Are their products designed for optical turbulence? – Are the given models tuned for the polar atmosphere?

4. • Many Global NWP Models Cover Antarctica –ECMWF Global model (25 km) –UK Met Office Global Model (40 km) –NCEP (National Centers for Environmental Prediction) Global Forecasting System (GFS) (~55 km) –U.S Navy NOGAPS (~55 km) –Arpège (Metéo France) (20–250 km) –GME (German Weather Service) –GEM (Global Environmental Multiscale) Model (Canadian Met Center) (~33 km) –JMA Global Spectral Model (Japan) (20 km) + more!!

5. • Difficulties in Systems not Tailored for Antarctic Astronomical Applications – Model output may be unavailable or unavailable in necessary time frame – Resolution may be too coarse – Model physics not tuned for high latitudes – Model products not designed for optical turbulence forecasting

6. The Antarctic Mesoscale Prediction System (AMPS)  Real-time mesoscale modeling system designed specifically for Antarctica  Purpose: Support of weather forecasting and scientific activities for the U.S. Antarctic Program (USAP)  Primary users  USAP Forecasters SPAWAR— Space and Naval Warfare Systems Center Scientists and graduate students  International forecasters

7. Air and Marine Forecast Users New York Air National Guard LC-130 McMurdo U.S. Air Force C-17 McMurdo Dronning Maud Land— Polarstern

8. • AMPS Applications for Research & Development Important component: AMPS forecast archive (from 2001) – Meteorological investigations: Case and process studies – Model and forecast evaluation – Development of polar modifications – Model-based climatologies

9. • AMPS Applications for Research & Development (cont’d) Comparison of Polar WRF V2.2.1 v. Polar WRF V3.0.1 Version 2.2.1 Version 3.0.1 Forecast 2-m T errors for South Pole (Winter 2008 test period) Nomimal improvement with 3.0.1

10.  AMPS Use by International Antarctic Programs ProgramLocations • Italy Terra Nova Bay (PNRA, Italian Air Force) • Australia Casey, Davis, Mawson (Bureau of Meteorology) • UK Rothera (British Antarctic Survey) • Germany Neumayer (German Weather Service) • Chile Eduardo Frei (Chilean Meteorological Direction) • South Africa Capetown, SANAE (S. African Weather Service) • DROMLAN Dronning Maud Land (Dronning Maud Land Air Network)

11. Support for DROMLAN— Dronning Maud Land Air Network (Forecasting by German Weather Service) Ships Germany Norway Russia Sweden India Finland Japan Belgium South Africa UK Do 228 C-130 Iljushin76 Basler DC-3 Traverses

12. • AMPS Forecast Grids 60 km 20 km + AGAP South 60-km, 20-km grids 20-km, 6.7-km, 2.3-km grids

13. 6.7 km AMPS Grids— Western Ross Sea and Ross Island Mario Zucchelli Station (Baia Terra Nova) • 2.2 km

14. AMPS Web Page www.mmm.ucar.edu / rt / amps

15. • AMPS Products – Surface and upper-air charts: Winds, temp, cloud, moisture, precip, etc. – Soundings and profiles – Meteograms – Tables – Cross-sections – Optical turbulence products?

16. AMPS Meteogram— AGAP South (-84.50, 77.35) 4 Aug 1200 UTC forecast 120 hr  Surface temp, dewpoint

17. 500 hPa Heights/Vorticity 4 Aug 2008 1200 UTC forecast (120 hr)

18. South Pole Soundings 4 Aug 2008 1200 UTC forecast (36 hr)

19. AMPS Mesoscale Model: WRF • Weather Research and Forecasting Model • www.wrf-model.org AMPS Forecasts Frequency: 2 / day Initializations: 0000 & 1200 UTC Duration: 36–120 hours

20. WRF/ARW Registered Users WRF User Participation Registered Users (Aug. 2008) U.S. Universities, Government labs, private sector 2894 Non-U.S. users 4778 Total 7672 Countries: 113 • 2002 2003 2004 2005 2006 2007 2008 Over 3200 active subscribers to wrf-news@ucar.edu Over 400 e-mail inquiries/month to user support group

21. Worldwide WRF User Participation 113 Countries (August 2008)

22. AMPS Data Assimilation • System – WRF-Var : 3-dimensional variational data assimilation (3DVAR) system – Ability to ingest direct and indirect observations • Observation Types – Standard surface obs (e.g, METAR, station reports),AWS obs, and upper-air (radiosonde) – Ships, buoys, aircraft (e.g., AMDAR) – Geostationary satellite cloud-track winds and MODIS polar winds – AMSU-A radiances (for study purposes) – COSMIC radio occultations

24. • WRF Polar Modifications for AMPS – Goal: Better representation of polar atmospheric conditions and processes Polar conditions generally have not been reflected in development of models over mid-latitudes – Polar mods – Fractional sea ice representation – Land Surface Model (Noah LSM) changes  Latent heat of sublimation used over ice surfaces  Adjustment of snow density, heat capacity, and thermal diffusivity (subsurface)

25. WRF Polar Modifications for AMPS (cont’d) LSM Adjustments (cont’d)  Assumption of ice saturation for calculating sfc saturation mixing ratios over ice  Increased snow albedo and emissivity – Modified initialization of low-level air temps and cycling of subsurface soil temps – Decreased shortwave radiation scattering – Stability-dependent formulation of thermal roughness length (z0t)

26. AMPS Use for Optical Turbulence Forecasting: Issues • No previous forecasting in AMPS of optical turbulence or seeing – What quantities/parameters specifically are needed? – What can be derived, in real time, from model output? • Unknown how well model resolution can provide for accurate parameter forecasts – Is a minimum vertical or horizontal resolution needed for acceptable accuracy? – Need to verify forecasts of parameters

27. 1–20 21–46 Levels AMPS WRF vertical levels/ distribution Full levels: 46 Model top: 10 mb Layer thickness (m)

28. AMPS Use for Optical Turbulence Forecasting: Issues (cont’d) • Restrictions on increasing model resolution or new forecast grids – Computer resources limited – Cannot hurt time-to-forecast: USAP forecaster needs are the priority – 1-way forecast nests a possibility for limited areas and periods 1-way nest would run after the main forecast

29. Summary • AMPS: Mesoscale NWP over Antarctica • High-resolution forecasts tuned for polar conditions with products tailored for users • AMPS: Possible tool for forecasting for astronomy or optical turbulence in Antarctica – Forecast parameter products or specific met information may be provided on web site – Caveats No coverage north of 40S Priority to USAP and related needs