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

In this study the crosswind (U perpendicular to) is determined from the time-lag correlation function [r(12)(tau))] measured by a dual large-aperture scintillometer; U perpendicular to is defined as the wind component perpendicular to a path-in this case, the scintillometer path. A scintillometer obtains a path-averaged U perpendicular to, which for ome applications is an advantage compared to other wind measurement devices. Four methods were used to obtain U perpendicular to: 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 perpendicular to by comparing r(12)(tau) of a measurement to r(12)(tau) of a theoretical model. The U perpendicular to values obtained from the scintillometer were validated with sonic anemometer measurements. The best results were obtained by the zero-slope method for U perpendicular to, < 2ms(-1) and by the lookup table method for U perpendicular to > 2ms(-1). The Briggs method also showed promising results, but it is not always able to obtain U perpendicular to. The results showed that a high parallel wind component (>2.5 ms(-1)) on the scintillometer path can cause an overestimation of U perpendicular to mainly for low U perpendicular to values <2 ms(-1)).