Mesoscale Numerical Weather Prediction over Antarctica: AMPS and Support for Groundbased Astronomy

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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
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Antarctica and Topography
McMurdo Station
Topography from NASA ICESat (Ice, Cloud, and
Elevation Satellite)
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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?
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• 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) (20250 km)
• GME (German Weather Service)
• GEM (Global Environmental Multiscale) Model
  (Canadian Met Center) (33 km)
• JMA Global Spectral Model (Japan) (20 km)
  more!!

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• 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

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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
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Air and Marine Forecast Users
New York Air National Guard LC-130 McMurdo
U.S. Air Force C-17 McMurdo
Dronning Maud Land Polarstern
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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
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AMPS Applications for Research Development
(contd)
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 Locations
• 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)

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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
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AMPS Forecast Grids
60 km
20 km

AGAP South
60-km, 20-km grids
20-km, 6.7-km, 2.3-km grids
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6.7 km
AMPS Grids Western Ross Sea and Ross Island
Mario Zucchelli Station (Baia Terra Nova)

2.2 km
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AMPS Web Page
www.mmm.ucar.edu / rt / amps
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• AMPS Products
• Surface and upper-air charts Winds, temp,
  cloud, moisture, precip, etc.
• Soundings and profiles
• Meteograms
• Tables
• Cross-sections
• Optical turbulence products?

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AMPS Meteogram AGAP South (-84.50, 77.35) 4
Aug 1200 UTC forecast 120 hr
? Surface temp, dewpoint
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500 hPa Heights/Vorticity 4 Aug 2008 1200 UTC
forecast (120 hr)
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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 36120 hours
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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_at_ucar.edu Over 400 e-mail
inquiries/month to user support group
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Worldwide WRF User Participation
113 Countries (August 2008)
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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

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• 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)

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• WRF Polar Modifications for AMPS (contd)
• LSM Adjustments (contd)
• ? 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)

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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
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120 2146 Levels
AMPS WRF vertical levels/ distribution Full
levels 46 Model top 10 mb
Layer thickness (m)
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AMPS Use for Optical Turbulence Forecasting
Issues (contd) 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
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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
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