TIME STEP VARIATIONS OF WINDS, HEIGHTS, AND TEMPERATURES IN THE NATIONAL METEOROLOGICAL CENTER PRIMITIVE EQUATION FORECAST MODEL.
Abstract
Several series of consecutive values of the forecast fields are extracted for a subgrid of the hemispheric forecast grid. Statistics of the change in one time step of each field are computed at various pressure levels and at different periods during a 37 hour forecast. The purpose of the analysis is to determine whether the time step variations are small enough to permit the use of instantaneous values of the forecast quantities, or whether some type of time-smoothing is necessary. It is found that the winds and temperatures forecast by the model change from one time step to the next in such a manner that instantaneous values of these quantities may be used. The geostrophic wind derived from the forecast height field varies sufficiently during a period of one or two hours so that instantaneous values of this wind are not considered useful. The height field on isobaric surfaces undergoes a non-meteorological variation with a period of about three hours and an average amplitude of about fifteen meters. At some gridpoints the amplitude may be more than twice this value. In using the forecast heights consideration must therefore be given to the possible effects of this high frequency oscillation. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1966
- Accession Number
- AD0648638
Entities
People
- James E. Mcdonell
- John E. Newell