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

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AMPS Capabilities and Application Issues

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Summary

Antarctica and Topography

• McMurdo Station

Topography from NASA ICESat (Ice, Cloud, and Elevation Satellite)

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?

• 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!!

• 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

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

Air and Marine Forecast Users

New York Air National Guard LC-130 McMurdo U.S. Air Force C-17 McMurdo Dronning Maud Land —

Polarstern

• 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

• 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

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AMPS Use by International Antarctic Programs

Program

• Italy (PNRA, Italian Air Force) • Australia (Bureau of Meteorology) • UK (British Antarctic Survey) • Germany (German Weather Service) • Chile (Chilean Meteorological Direction) • South Africa (S. African Weather Service) • DROMLAN (Dronning Maud Land Air Network)

Locations

Terra Nova Bay Casey, Davis, Mawson Rothera Neumayer Eduardo Frei Capetown, SANAE Dronning Maud Land

Support for DROMLAN — Dronning Maud Land Air Network

(Forecasting by German Weather Service)

Germany Norway Russia Sweden India Finland Japan Belgium South Africa UK

Basler DC-3 Traverses Iljushin76 Ships Do 228 C-130

• AMPS Forecast Grids

60 km 20 km

+ AGAP South 60-km, 20-km grids 20-km, 6.7-km, 2.3-km grids

6.7 km Mario Zucchelli Station (Baia Terra Nova)

•

2.2 km

AMPS Grids — Western Ross Sea and Ross Island

AMPS Web Page

www.mmm.ucar.edu / rt / amps

• AMPS Products – Surface and upper-air charts: Winds, temp, cloud, moisture, precip, etc.

– Soundings and profiles – Meteograms – Tables – Cross-sections

– Optical turbulence products?

AMPS Meteogram — AGAP South (-84.50, 77.35) 4 Aug 1200 UTC forecast 120 hr

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Surface temp, dewpoint

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

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

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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

WRF User Participation

Registered Users (Aug. 2008) U.S. Universities, Government labs, private sector 2894 Non-U.S. users 4778 Total 7672 Countries: 113

9000 8000 7000 6000 5000 4000 3000 2000 1000

WRF/ARW Registered Users

0 Jan

2001

May 1 Se p 01 Jan

2002 2003 2004 2005 2006 2007 2008

May Se p 02 Jan -0 3 May -0 3 Se p 03 Jan -0 4 May -0 4 Se p 04 Jan -0 5 May -0 5 Se p 05 Jan -0 6 May -0 6 Se p 06 Jan -0 7 May -0 7 Se p 07 Jan -0 8 May -0 8

Over 3200 active subscribers to [email protected]

Over 400 e-mail inquiries/month to user support group

Worldwide WRF User Participation

113 Countries (August 2008)

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

• 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)

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 (z 0t )

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

1 –20 21–46 Levels AMPS WRF vertical levels/ distribution

Full levels: 46 Model top: 10 mb

Layer thickness (m)

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

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

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No coverage north of 40S

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Priority to USAP and related needs