GPSRO Usage at Naval Research Laboratory (NRL)

Deterministic models assimilating RO

  • Global only spectral model t359l50:
    • ~37km horizontal resolution
    • 50 vertical model levels, top at 0.01hPa
    • Four forecasts delivered per day at: 00, 06, 12, 18UTC

Data assimilation method

  • 4D-Var with a 6-hour assimilation window
  • Cutoff times:
Synoptic time 00Z 06Z 12Z 18Z
Real 6h35 6h25 6h35 6h25
Post 11h10 11h20 11h10 11h20

RO quantity assimilated

  • Bending angle
  • 1D operator
  • Tangent point drift
  • No vertical thinning
  • No bias correction

Observation error characteristics

  • Below 10km impact height: ob*20%
  • Above 10km impact height: max(ob*1.5%, 6microradians)


Total moist error norm (J/kg) from surface to ~150hPa show a consistent positive impact, though the GNSS sensors do trail the microwave and IR satelite sounders in impact for this metric. Of the GNSS sensors the COSMIC give the largest impact mostly due to their use below 8km.

NRL_FNMOC_ops_cost_innov_total_20120801 NRL_FNMOC_ops_cost_innov_total_per_ob_20120801


The near real-time monitoring for NRL is here (external link).