Observing crosswind over urban terrain using scintillometer and Doppler lidar

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Abstract

In this study, the crosswind (wind component perpendicular to a path, <i>U</i><sub>&bot;</sub>) is measured by a scintillometer and Doppler lidar above the urban environment of Helsinki, Finland, for 3 weeks. The scintillometer allows acquisition of a path-averaged value of <i>U</i><sub>&bot;</sub> (<span style="border-top: 1px solid #000; color: #000;"><i>U</i><sub>&bot;</sub></span>), while the Doppler lidar allows acquisition of path-resolved <i>U</i><sub>&bot;</sub> (<i>U</i><sub>&bot;</sub> (<i>x</i>), where <i>x</i> is the position along the path). The goal of this study is to evaluate the applicability of scintillometer <span style="border-top: 1px solid #000; color: #000;"><i>U</i><sub>&bot;</sub></span>-measurements for conditions where <i>U</i><sub>&bot;</sub> (<i>x</i>) is variable. If the scintillometer is applicable in such variable-wind conditions, it can also be used in the urban environment. Two methods were applied to obtain <span style="border-top: 1px solid #000; color: #000;"><i>U</i><sub>&bot;</sub></span> from the scintillometer signal; the cumulative spectrum method (relies on scintillation spectra), and the lookup table method (relies on time-lagged correlation functions). Both methods compared reasonably well with the Doppler lidar measurements, especially considering the challenging urban environment in which they were measuring; with RMSE of 0.71 and 0.73 m s<sup>&minus;1</sup>. This indicates that both measurement technologies are able to obtain <span style="border-top: 1px solid #000; color: #000;"><i>U</i><sub>&bot;</sub></span> in the complex urban environment. The in detail investigation of four cases indicate that the cumulative spectrum method is less susceptible to a variable <i>U</i><sub>&bot;</sub> (<i>x</i>) than the lookup table method. However, the lookup table method can be adjusted to improve its capabilities to obtain <span style="border-top: 1px solid #000; color: #000;"><i>U</i><sub>&bot;</sub></span> for conditions where <i>U</i><sub>&bot;</sub> (<i>x</i>) is variable.

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APA

Van Dinther, D., Wood, C. R., Hartogensis, O. K., Nordbo, A., & O’Connor, E. J. (2015). Observing crosswind over urban terrain using scintillometer and Doppler lidar. Atmospheric Measurement Techniques, 8(4), 1901–1911. https://doi.org/10.5194/amt-8-1901-2015

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