Status of Bracketing OSSEs at NCEP for Several DWL Notional Concepts

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Status of Bracketing OSSEs at NCEP for Several
DWL Notional Concepts

• G. D. Emmitt
• M. Masutani, S. Lord
• WG on Space-based Lidar Winds
• Oxnard, CA
• 7-9 February, 2001

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General Status

• Current (i.e.1993) data simulation complete
• RAOBs, ACARS, CTW(?), TOVS(1B), Surface
• All simulated DWL observations complete
• bracketing concepts with ?m ltlt 1 m/s
• Calibration of OSSE nearly complete
• Temperature bias still unresolved
• Initial DWL impact on analyses being assessed for
  bracketing concepts

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Key Calibration Issues

• Are the statistics of the simulated data similar
  to those of the real data?
• Are the impacts of individual data sets on
  analyses similar in both real OSEs and
  simulated OSEs?

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Relative importance of tropospheric wind
observations in OSE segment

• RAOB winds in the NH
• impact on model wind field
• impact on derived temperature
• CTWs in SH NH
• impact on winds
• impact on temperature

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Review of bracketing OSSE strategy

• Technology neutral but with realistic
  observational coverage
• 4 basic coverage concepts plus an OSSE reference
  data set
• Three series of impact experiments
• Coverage (?m 0 m/s ?s 2 m/s)
• Accuracy (?m 2 or 5 m/s ?s 2 m/s)
• Systematic Errors (?m 2 or 5 m/s ?s 2 m/s
  plus correlated errors)

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Figure of merit

• ?o2 ?m2/Ns ?s2/Ne
• ?o2 is total observation error for use in the
  SSI cost function (assigned a value if
  necessary).
• ?m2 is the instruments observation error for the
  target motion within the illuminated volume
• ?s2 is the variance of the winds within the
  effective resolution grid of the assimilating
  model
• Ns is the number of independent samples that are
  effective in reducing the LOS measurement error
• Ne is the number of independent samples that are
  effective in reducing the error in estimating the
  average LOS within the sampled area.

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Example

• ?o2 ?m2/Ns ?s2/Ne
• ?m 10 m/s (Sqrt(?m2/Ns) 1 m/s)
• ?s 3 m/s
• N 100
• Cluster ?o 3.2 m/s
• Distributed ?o 1.4 m/s