A Simple Scheme for Objective Analysis in Curved Flow

Abstract

An objective analysis scheme has been developed which combines use of different weighting functions, two of which are anisotropic (elliptical and banana-shaped). The “effective” distance between a grid point and an observation point used for the anisotropic functions may be applied in any objective analysis scheme which uses distance to calculate weights or correlations, but a successive-correlation scheme is used here as a vehicle for testing. This relatively simple and computationally inexpensive scheme produces wind and moisture analyses in which along-flow autocorrelation is accentuated, especially in regions of curved flow, and thus simulates conventional subjective analysis procedures. Sample analyses from a case study are presented which demonstrate the improvement which may result from using this scheme rather than one with the circular weighting function alone. In tests with an analytically defined, curving jet stream, the multiple weighting function scheme with the “banana” function was... Abstract An objective analysis scheme has been developed which combines use of different weighting functions, two of which are anisotropic (elliptical and banana-shaped). The “effective” distance between a grid point and an observation point used for the anisotropic functions may be applied in any objective analysis scheme which uses distance to calculate weights or correlations, but a successive-correlation scheme is used here as a vehicle for testing. This relatively simple and computationally inexpensive scheme produces wind and moisture analyses in which along-flow autocorrelation is accentuated, especially in regions of curved flow, and thus simulates conventional subjective analysis procedures. Sample analyses from a case study are presented which demonstrate the improvement which may result from using this scheme rather than one with the circular weighting function alone. In tests with an analytically defined, curving jet stream, the multiple weighting function scheme with the “banana” function was...