Applications of the Barnes Objective Analysis Scheme. Part III: Tuning for Minimum Error

Abstract Procedures for tuning a successive corrections objective analysis scheme, described in Part I, are applied to the array of North American rawinsonde stations. Tuning is investigated for three types of Barnes schemes (two-, three-, and four-pass schemes) and for an equivalent four-pass scheme developed by Caracena. Each of the schemes uses an iteration parameter equal to 1, and each considers the influence of all observations within at least 2500 km of the interpolation point. Analysis accuracy is investigated for “errorless observations” of a simulated 300-mb height field containing a Rossby-scale wave with one of its ridges amplified to produce an asymmetric distribution of the height gradient across a circular region of locally lower heights representing a synoptic-scale low. Root-mean-square errors are evaluated at grid points for analyses of pressure height, height gradient, and the Laplacian of height over a range of values for the weight function's scale-length parameter α. Because the anal...