Mesoscale Numerical Weather Prediction

over Antarctica: AMPS and Support for

Ground-based Astronomy

Antarctic NWP and AMPS

AMPS Capabilities and Application Issues

Summary

Jordan G. Powers

Mesoscale and Microscale Meteorology DivisionEarth and Sun Systems Laboratory

National Center for Atmospheric Research Boulder, Colorado, USA

Antarctica and Topography

Topography from NASA ICESat

(Ice, Cloud, and Elevation Satellite)

•McMurdo Station

• Issues in Antarctic NWP: Forecastingfor 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?

I. Antarctic NWP and AMPS (Antarctic Mesoscale Prediction System)

• 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 ForecastersSPAWAR— Space and Naval Warfare Systems Center

Scientists and graduate students

International forecasters

Air and Marine Forecast Users

U.S. Air Force C-17McMurdo

New York Air National GuardLC-130 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

Forecast 2-m T errors for South Pole (Winter 2008 test period)

Nomimal improvement with 3.0.1

Version 2.2.1 Version 3.0.1

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)

• South Africa Capetown, SANAE (S. African Weather Service)

• DROMLAN Dronning Maud Land (Dronning Maud Land Air Network)

Basler DC-3 Traverses

Ships

Do 228

Iljushin76 C-130

Support for DROMLAN— Dronning Maud Land Air Network (Forecasting by German Weather Service)

Germany NorwayRussia SwedenIndia FinlandJapan BelgiumSouth Africa UK

60-km, 20-km grids 20-km, 6.7-km, 2.3-km grids

• AMPS Forecast Grids

60 km

20 km

+

AGAP South

AMPS Grids—Western Ross Sea and Ross Island

2.2 km

6.7 kmMario Zucchelli Station (Baia Terra Nova)

•

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

Surface temp, dewpoint

500 hPa Heights/Vorticity

4 Aug 20081200 UTC forecast

(120 hr)

South Pole Soundings

4 Aug 20081200 UTC forecast

(36 hr)

AMPS Mesoscale Model: WRF

Weather Research and Forecasting ModelWeather Research and Forecasting Model

www.wrf-model.org

AMPS ForecastsAMPS Forecasts

Frequency: 2 / dayFrequency: 2 / day

Initializations: 0000 & 1200 UTC Initializations: 0000 & 1200 UTC

Duration: 36Duration: 36––120 hours 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

Over 3200 active subscribers to wrf-news@ucar.edu

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

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

WRF/ARW Registered Users

2001 2002 2003 2004 2005 2006 2007 2008

Worldwide WRF User Participation

113 Countries(August 2008)

• 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

AMPS Data Assimilation

• 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 (z0t)

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

AMPS WRF vertical levels/ distribution

Full levels: 46

Model top: 10 mb

Layer thickness (m)

1–20 21–46 Levels

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 forecasterneeds are the

priority

– 1-way forecast nests a possibility for limited areas and periods

1-way nest would run after the main forecast

SummarySummary

• • AMPS: Mesoscale NWP over AntarcticaAMPS: Mesoscale NWP over Antarctica

• • High-resolution forecasts tuned for polar High-resolution forecasts tuned for polar conditions with products tailored for usersconditions with products tailored for users

• • AMPS: Possible tool for forecasting for AMPS: Possible tool for forecasting for astronomy or optical turbulence in Antarcticaastronomy or optical turbulence in Antarctica

– Forecast parameter products or specific met information may be provided on web site

– Caveats No coverage north of 40SNo coverage north of 40S

Priority to USAP and related needsPriority to USAP and related needs