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

Monitoring

External monitoring web pages

• http://qc.kishou.go.jp/Satmonit/seqgraph_scat.html
  No password required

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

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.

References