Objective Analysis Technique in Sigma Coordinates.
ENVIRONMENTAL PREDICTION RESEARCH FACILITY (NAVY) MONTEREY CALIF
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A three-step objective analysis technique for initializing Fleet Numerical Weather Centrals Primitive Equation Forecast Model in the 63x63 Northern Hemisphere Polar Stereographic Grid is described. In the first step, an analysis is performed at 10 mandatory pressure levels. In the second step, the mandatory pressure level heights are transformed into sigma coordinates by using a mass structure conversion procedure which describes the physical properties of an air column through static stability parameters over defined pressure increments. In the third step, raw data are converted to sigma coordinates by an identical procedure and reanalyzed in sigma coordinates by using the transformed pressure level analysis as initial guess. The applied numerical analysis method is based on the pattern-conserving analysis technique FIB Field by Information Blending which allows wind and height reports to be treated as independent information sets and to be analyzed simultaneously.