ATMOSPHERIC FLOW PATTERNS AND THEIR REPRESENTATION BY SPHERICAL-SURFACE HARMONICS.

Abstract

Abstract : Some theoretical and empirical investigations of large-scale flow patterns in the atmosphere are presented. These investigations are characterized primarily by the use of spherical coordinates. One of the assumptions on which the theoretical investigations are based is that of an undisturbed westerly flow of constant angular velocity. This assumption is tested with 10,000-ft maps and is found to hold reasonably well between the latitudes 30 degrees N and 60 degrees N. Interrelationships between the strength of this flow and other meteorological parameters are studied statistically. The theoretical investigations yield a solution for the stream function (or pressure) in the form of a superposition of spherical harmonics. Consequently, a method of spherical-harmonic analysis is described and applied to several weather maps. These analyses show that: (a) spherical-harmonic analysis affords a powerful method of representing a large amount of data with relatively few numbers and could become a useful tool in climatology or in analogue investigations; (b) the part of the pressure field that is 'forced' by the solenoidal field is predicted reasonably well by the theory; (c) the application of the theory in its present form to day-to-day forecasting is hampered considerably by the lack of data from large parts of the earth. Tables are presented to facilitate future applications of spherical-harmonic analysis. (Author)

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