RESEARCH IN NUMERICAL, DYNAMICAL, AND OPERATIONAL WEATHER FORECAST PROCEDURES.
Final rept. 15 Jan 66-14 Mar 67,
RESEARCH TRIANGLE INST DURHAM N C
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An analysis of various numerical prediction errors of the Global Weather Center, six-level model was performed. The most persistent errors in 12-hour vertical motions ranged between plus or minus 40 mbs at 850 mbs and plus or minus 25 mbs at 500 mbs. Up to 50 of this error was accounted for by slight changes in stability and diabatic heating produced 12-hour vertical displacements of the same order of magnitude as the error. A case study of the effect of the omission of vertical advection term in the vorticity equation showed that the most significant contribution of this term was in the form of cyclonic vorticity, and that these contributions fell in regions where anticyclonic vorticity was overestimated, reducing this error by as much as 45. However, a scatter plot of the vorticity error versus the vertical advection term showed a preponderance of cyclonic contribution by vertical advection but these fell equally well in regions where cyclonic and anticyclonic vorticity were overestimated. There was a strong correlation between heating and cooling distribution and surface flow patterns. The height errors also correlated with the heating distribution. It was shown that latent and surface heating accounted for a major portion of the positive height error. Author