A Method to Decompose the Spatial Characteristics of Meteorological Variables within a Limited Domain

Thomas W. Bettge National Center for Atmospheric Research, Boulder, CO 80307

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David P. Baumhefner National Center for Atmospheric Research, Boulder, CO 80307

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Abstract

The design of a digital filter is outlined and its application as a band-pass filter to separate various scales from an atmospheric field in a limited domain is discussed. The accuracy of the filter is demonstrated by decomposing both a function with specified wave components and a 500 mb geopotential field within a 90°longitudinal area of the globe. The boundary effects of the non-periodic domain are not negligible, but tests using various boundary conditions show that little contamination exists inside 7–10 grid points from the boundaries. The suitability of the technique to examine the spatial wavenumber characteristics of a geopotential field within a limited domain is demonstrated.

Abstract

The design of a digital filter is outlined and its application as a band-pass filter to separate various scales from an atmospheric field in a limited domain is discussed. The accuracy of the filter is demonstrated by decomposing both a function with specified wave components and a 500 mb geopotential field within a 90°longitudinal area of the globe. The boundary effects of the non-periodic domain are not negligible, but tests using various boundary conditions show that little contamination exists inside 7–10 grid points from the boundaries. The suitability of the technique to examine the spatial wavenumber characteristics of a geopotential field within a limited domain is demonstrated.

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