Evaluation of Several “Single-Pass” Estimators of the Mean and the Standard Deviation of Wind Direction

Abstract

Proposed single-pass methods for estimating the mean (D?) and the standard deviation (σd) of wind direction and other problems in wind statistics have been evaluated using extensive field data. It can be concluded that Mardia's methods for estimating D? and σd provide good estimators in practical application. Yamartino's empirical method also provides a good estimator of σd. The relationship between the vector mean wind speed Vv and the scalar mean wind speed Va has been investigated in connection with σd and the standard deviation of the crosswind velocity σv. It is found that Kampé de Fériet-Frenkiel's equation, which represents the relation for Vv and Va in terms of σv, holds for the field data, so we can get an estmator of σv from observed Vv and Va. The ratio of Vv/Va is roughly related to the standard deviation of wind direction, and the relation can be expressed as Vv/Va=exp(?0.5σd2) for σd<20 deg.