jmamodel

Scatterometer use in NWP at JMA

Physical characteristics

Global Spectral Model (GSM)

  • Spectral model
  • Horizontal resolution: TQ959 (0.1250° (≈ 13 km), Reduced Gaussian Grid)
  • Vertical resolution: 128 vertical levels, sigma-p hybrid coordinate, lid at 0.01 hPa

Meso-Scale Model (MSM)

  • Grid-point model (817 E-W × 661 N-S), grid centred on Japan
  • Horizontal resolution: 5 km at 60N and 30N
  • Vertical resolution: 96 vertical levels, hybrid terrain-following coordinate, lid ≈ 37.5 km

Local Forecast Model (LFM)

  • Grid-point model (1531 E-W × 1301 N-S), grid centred on Japan
  • Horizontal resolution: 2 km at 60N and 30N
  • Vertical resolution: 76 vertical levels, hybrid terrain-following coordinate, lid ≈ 22 km

Data assimilation method

Global Spectral Model (GSM – Global Analysis)

  • Hybrid LETKF/4D-Var, 6-hr data assimilation window, increment resolution TL319 (≈ 55 km)
  • Analysis times: 00, 06, 12, 18 UTC
  • Time window: 6 hrs (centred on nominal analysis time)
  • Time constraints (model runtime):
    • Early analysis: 40 min before time window ends
    • Cycle analysis: 8 hr 50 min after time window ends at 00,12 UTC, and 4 hr 50 min after time window ends at 06,18 UTC

Meso-Scale Model (MSM – Meso-scale Analysis)

  • 4D-Var, 3-hr data assimilation window, increment resolution 15 km, 50 vertical levels
  • Analysis times (T): 00, 03, 06, 09, 12, 15, 18, 21 UTC
  • Time window: 3 hrs (ended at nominal analysis time, e.g. 06-09 UTC for 09 UTC run)
  • Time constraints (model runtime):
    • 50 min after time window ends

Local Forecast Model (LFM – Local Analysis)

  • The three-hour analysis cycle repeats hourly assimilation with hybrid 3D-Var and one-hour forecasts, 3-hr data assimilation window, increment resolution 5 km, 48 vertical levels
  • Analysis times (T): 00, 01, 02, 03, 04, 05, 06, 07, 08, 09, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 UTC
  • Time window: 3 hrs (ended at nominal analysis time, e.g. 06-09 UTC for 09 UTC run)
  • Time constraints (model runtime):
    • 30 min after time window ends

Scatterometers assimilated

Scat name Product Models assimilated
ASCAT-B OSI-SAF Level 2 BUFR 25-km equivalent-neutral wind product produced by KNMI. GSM
OSI-SAF Level 2 BUFR Coastal 12.5-km equivalent-neutral wind product produced by KNMI. MSM/LFM
ASCAT-C OSI-SAF Level 2 BUFR 25-km equivalent-neutral wind product produced by KNMI. GSM
OSI-SAF Level 2 BUFR Coastal 12.5-km equivalent-neutral wind product produced by KNMI. MSM/LFM

Monitoring

External monitoring web pages

Generic Quality Control

Blacklisting

  • All wind speeds outside range 0-25 m/s
  • All observations made over ice according to the JMA sea ice analysis
  • All observations with SST less than 274.15 K according to Merged satellite and in-situ data Global Daily Sea Surface Temperature (MGDSST) in GSM and High-resolution Merged satellite and in-situ data Global Daily Sea Surface Temperature (HIMSST) in MSM

Ambiguity removal

  • Performed by comparison with JMA background fields before assimilation.

Bias correction

  • None

Thinning

  • Thinning distances are about 110 km (1 degree longitude at the equator) in GSM, and about 45 km (0.5 degree longitude around Japan) in MSM and LFM

Background check

  • Observation of which first guess departure is larger than 5 m/s is rejected.
  • A specialized quality control named ‘Group QC’ (Ohhashi 2004) is performed for the wind direction.

Specific Quality Control

Model GSM MSM LFM
Scat name ASCAT-B/C ASCAT-B/C ASCAT-B/C
Operational since November 2013 (Metop-B), December 2019 (Metop-C) December 2015(Metop-A,Metop-B), December 2021 (Metop-C)

March 2023
Observation error U/V 4.0 m/s (≤ 15 m/s)
6.0 m/s (> 15 m/s)
3.0 m/s
Wind speed range 0-25 m/s
Bias corrected? No
Crosstrack cells used All nodes
QC thresholds Check supplied wind vector QC flag

Observation Operator

Interpolation

  • Observations are assimilated as winds at a height of lowest model level (≈ 10 m) in GSM and 10 m height in MSM and LFM. 10 m real wind components are calculated using the stability functions of Louis et al. (1982). Model wind fields are horizontally interpolated to the observation location using standard linear interpolation of the surrounding four grid points.

Analysis Increments

  • Observations are considered as real winds.

History of Changes

The list includes the main scatterometer or model changes implemented operationally at JMA.

28/03/23

ASCAT-B/C coastal wind data assimilated in LFM.
14/03/23

GSM upgrade from TL959L128 to TQ959L128
22/03/22

The vertical levels of MSM enhanced from 76 to 96
30/03/21 GSM upgrade from TL959L100 to TL959L128
29/07/20 Addition of ScatSat-1 in GSM
11/12/19 Hybrid LETKF/4D-Var system introduced for GSM. Addition of Metop-C in GSM.
26/03/19 ASCAT-A/B coastal wind data assimilated in MSM. HIMSST products introduced in MSM in place of MGDSST products.
28/02/18 The vertical levels of MSM enhanced from 50 to 76
24/12/15 ASCAT-A/B 25 km data assimilated in MSM
08/10/15 Extension of wind speed upper limit from 15 to 25 m/s and removal of
observational error inflation in the Southern Hemisphere poleward of
30S in GSM
18/03/14 GSM upgrade from TL959L60 to TL959L100 and raise of the model top level from 0.1 hPa to 0.01 hPa
28/11/13 ASCAT-B 25 km data assimilated in GSM
28/03/13 MSM forecast area extended from 721(E-W) × 577(N-S) to 817(E-W) × 661(N-S) with same grid length
28/07/09 ASCAT-A 25 km data assimilated in GSM

References

JMA, 2023: ‘Outline of the operational numerical weather prediction at the Japan Meteorological Agency’. Appendix to WMO Technical Progress Report on the Global Data-processing and Forecasting System and Numerical Weather Prediction Research. Japan Meteorological Agency, Tokyo, Japan.
Available on http://www.jma.go.jp/jma/jma-eng/jma-center/nwp/outline2023-nwp/index.htm
Louis, J. F., M. Tiedtke, and J.-F. Geleyn, 1982: A short history of
the PBL parameterization at ECMWF. Workshop on planetary boundary layer
parameterization, November 1981, ECMWF, Reading, England.
Ohhashi, Y. 2004: Assimilation of QuikSCAT/SeaWinds Ocean Surface Wind Data into the JMA Global Data Assimilation System. RSMC Tokyo Typhoon Center Technical Review, NO. 7, Japan Meteorological Agency, pp 22-27. Available on http://www.jma.go.jp/jma/jma-eng/jma-center/rsmc-hp-pub-eg/techrev.htm