A Comparison of Several “Single-Pass” Estimators of the Standard Deviation of Wind Direction

Abstract

Computation of the standard deviation of wind direction σ_θ generally requires repeated consideration of the individual measurements of wind direction. This need for multiple passes through the data sample can create a storage problem for small or remote data acquisition systems. Statistical quantities that can be computed during a single pass through incoming wind speed and direction data are first reviewed, and relationships between these quantities are discussed. A single-pass estimator for σ_θ is then developed and found to correspond to within ±2% of conventional, two-pass σ_θ computations for unimodal angular distributions spanning the full σ_θ range of from 0 to 103.9°. Similar comparisons are presented for other, recently proposed estimators of σ_θ.