GPSRO Usage at CMA

Deterministic models assimilating RO 

• GRAPES (Global/ Regional Assimilation and PrEdiction System) of CMA
  • GRAPES forecast model:
    • Non-hydrostatic equations
    • Terrain-following coordinate
    • Arakawa-C(horizontal) and Charney-Phillips(vertical) grid
    • Model top at 32.5km
    • 37 vertical levels
    • Resolution 0.5°x 0.5 °(720*360)
    • Run four times per day (twice a day to 144 hours)
  • GRAPES-Var system:
    • Configuration of coordinate and grid is same to the forecast model
    • Resolution 1.125°x 1.125 °
    • Incremental digital filter initialization

Data assimilation method

• 3D-Var with a 6-hour time window (T±3h)

RO quantity assimilated

• Refractivity, 1D operator
• No tangent point drift
• QC in preprocessing refers to that of Mete. France
• Vertical thinning: 1 datum per analysis vertical layer
• No horizontal thinning
• Background check

Observation error characteristics

• Obs. Error is dependent on latitudes (low, high and mid) and height

Impact

• Analysis and forecast score show that RO data is one of the most important data at GRAPES.
• Adjoint sensitivity studies are not possible with the GRAPES now