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AMPS: A real-time application of WRF over Antarctica. Michael G. Duda, Kevin W. Manning, and Jordan G. Powers NCAR / MMM Division. NCAR-NCAS WRF Workshop. What is AMPS?. AMPS: Antarctic Mesoscale Prediction System Real-time system using WRF with polar modifications

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amps a real time application of wrf over antarctica
AMPS: A real-time application of WRF over Antarctica

Michael G. Duda, Kevin W. Manning, and Jordan G. Powers

NCAR / MMM Division

NCAR-NCAS WRF Workshop

what is amps
What is AMPS?
  • AMPS: Antarctic Mesoscale Prediction System
    • Real-time system using WRF with polar modifications
    • Twice-daily model runs (launched at 00 and 12 UTC)
      • Each run extends out to 120h
    • About 1 GB of plot products produced from each run and made available through web interface
      • Most products customized for forecasters
  • Goals of AMPS project
    • Support USAP weather forecasting
    • Improve Antarctic NWP

NCAR-NCAS WRF Workshop

1

overview
Overview
  • Model setup
  • Experiences
    • Increasing horizontal resolution and raising model top
    • Surface warm bias
  • Future improvements
    • Model sensitivity to radiation scheme

NCAR-NCAS WRF Workshop

2

model domain configuration
Model domain configuration

1

2

3

5

4

6

All nests are two-way interactive.

43 half-eta levels

10 hPa model top

NCAR-NCAS WRF Workshop

3

model domain configuration1
Model domain configuration

McMurdo

Station

1.7-km Ross Island nest

15-km Antarctic nest

NCAR-NCAS WRF Workshop

4

model options
Model options
  • WRF v3.0.1 with polar modifications (tuned for use in high latitudes; http://polarmet.mps.ohio-state.edu/PolarMet/pwrf.html)
    • Fractional sea ice
    • Improved treatment of heat transfer for ice sheets

Physics options

Dynamics options

NCAR-NCAS WRF Workshop

5

data assimilation
Data assimilation
  • WRF-Var for data assimilation on 45-km and 15-km grids
  • Assimilated observations include
    • “Conventional” observations (radiosonde, AWS, ship/buoy/aircraft)
    • Satellite obs (Meteosat 7,9; GOES-11,12; MODIS winds; QuikSCAT winds)
    • GPS RO soundings (refractivity)

NCAR-NCAS WRF Workshop

6

cycled soil temperatures
Cycled soil temperatures
  • GFS soil temperatures have generally been too warm in Antarctica
  • Solution: cycle the soil temperature field from one forecast to the next
  • Cycled soil temperatures have the effect of lowering soil temperature in model
    • However, observations of 2-m air temperature still showed a warm bias

NCAR-NCAS WRF Workshop

8

cycled soil temperatures1
Cycled soil temperatures

Soil temperature cycled over ~1 yr (?) using the Noah LSM

Soil temperature from GFS

0 - 10 cm layer

100 - 200 cm layer

NCAR-NCAS WRF Workshop

9

moving from a 60 km to a 45 km coarse grid
Moving from a 60-km to a 45-km coarse grid
  • In Nov 2008, increased horizontal resolution from 60-km in coarse grid to 45-km; all other nests increased proportionately
  • Raise model top from 50 hPa to 10 hPa, increase number of vertical levels from 31 to 44
    • Increase in model top originally motivated by satellite data assimilation
  • New configuration requires about 3.4 times as much computation (current wallclock time for one AMPS run ~4.5 h)

NCAR-NCAS WRF Workshop

11

new vertical level structure

AMPS vertical

coordinate

configuration

Fouradditional

layersbelow 1km

New vertical level structure

Significantly

thinner layers

(higher resolution)‏

near surface

Lowest 2 km

Older 31-level

configuration

New 44-level

configuration

NCAR-NCAS WRF Workshop

12

new vertical level structure1

AMPS vertical

coordinate

configuration

New vertical level structure

New configuration:

Model lid at 10 mb

Above 2 km

Damping layer in

top 7 km

Vertically propagating

waves damped, little

spurious reflection

Extending model top

to 10 mb improves

the assimilation

of satellite data

Old configuration:

Model lid at 50 mb

NCAR-NCAS WRF Workshop

13

new vertical level structure2
New vertical level structure
  • To remove strong reflections from model top, w-Rayleigh damping activated in top 7 km of the model

Vertical velocity cross section, no damping

Vertical velocity cross section, with w-Rayleigh damping

NCAR-NCAS WRF Workshop

14

performance of new setup
Performance of new setup

The 45-km / 10 hPa Ptop grid setup replaced the 60-km / 50 hPa Ptop setup on 3 Nov 2008

Oct 18

Nov 18

Nov 3

60-km, 50 hPa Ptop

45-km, 10 hPa Ptop

What impact did this change in grid structure have on the performance of forecasts?

NCAR-NCAS WRF Workshop

15

performance of new setup acc
Performance of new setup: ACC

In terms of 500 hPa height anomaly correlation, the new setup (10 hPa Ptop, 45-km coarse grid) is definitely an improvement

  • Differences in ACC (except for 00h) are statistically significant at the 5% level
  • “Climatology” computed from 31 days of 6-hourly FNL data between Oct 15 and Nov 15
  • NB: No data archived past 72h for 60-km setup

NCAR-NCAS WRF Workshop

15

performance of new setup1
Performance of new setup
  • What about in terms of error profiles?

24h

48h

72h

Zonal wind MAE (measured against radiosonde) for 20-km grid (blue) and 15-km grid (red)

NCAR-NCAS WRF Workshop

16

performance of new setup2
Performance of new setup
  • Zonal wind MAE (measured against MODIS winds)

NCAR-NCAS WRF Workshop

17

model issues surface warm bias
Model issues: surface warm bias
  • Increase land ice albedo from 70% to 80%

NCAR-NCAS WRF Workshop

18

model issues surface warm bias1
Model issues: surface warm bias
  • Increase land ice albedo from 70% to 80%

2-m temperature bias in 36-h forecasts (12-21 Jan 2009)

Courtesy: Julien Nicolas, OSU

NCAR-NCAS WRF Workshop

19

model issues surface warm bias2
Model issues: surface warm bias
  • Time series of model 2-m temperatures at Nico AWS from Jan 10 to Feb 6

NCAR-NCAS WRF Workshop

20

future work cam radiation scheme
Future work: CAM radiation scheme
  • KEVIN’S WORK WITH CAM RADIATION?

NCAR-NCAS WRF Workshop

22

slide22
Questions?

NCAR-NCAS WRF Workshop

23