Using the Time-Lag Correlation Function of Dual-Aperture Scintillometer Measurements to Obtain the Crosswind

Abstract

n this study the crosswind (U?) is determined from the time-lag correlation function [r12(τ)] measured by a dual large-aperture scintillometer; U? is defined as the wind component perpendicular to a path?in this case, the scintillometer path. A scintillometer obtains a path-averaged U?, which for some applications is an advantage compared to other wind measurement devices. Four methods were used to obtain U?: the peak method, the Briggs method, the zero-slope method, and the lookup table method. This last method is a new method introduced in this paper, which obtains U? by comparing r12(τ) of a measurement to r12(τ) of a theoretical model. The U? values obtained from the scintillometer were validated with sonic anemometer measurements. The best results were obtained by the zero-slope method for U? < 2 m s?1 and by the lookup table method for U? > 2 m s?1. The Briggs method also showed promising results, but it is not always able to obtain U?. The results showed that a high parallel wind component (>2.5 m s?1) on the scintillometer path can cause an overestimation of U? mainly for low U? values (<2 m s?1).