Observing crosswind over urban terrain using scintillometer and Doppler lidar
In this study, the crosswind (wind component perpendicular to a path, <i>U</i><sub>⊥</sub>) is measured by a scintillometer and estimated with Doppler lidar above the urban environment of Helsinki, Finland, for 15 days. The scintillometer allows acquisition of a path-...
| Main Authors: | , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2015-04-01
|
| Series: | Atmospheric Measurement Techniques |
| Online Access: | http://www.atmos-meas-tech.net/8/1901/2015/amt-8-1901-2015.pdf |
| Summary: | In this study, the crosswind (wind component perpendicular to a path,
<i>U</i><sub>⊥</sub>) is measured by a scintillometer and estimated with Doppler
lidar above the urban environment of Helsinki, Finland, for 15 days. The
scintillometer allows acquisition of a path-averaged value of <i>U</i><sub>⊥</sub> (<span style="border-top: 1px solid #000; color: #000;"><i>U</i><sub>⊥</sub></span>), while the lidar allows acquisition of path-resolved
<i>U</i><sub>⊥</sub> (<i>U</i><sub>⊥</sub> (<i>x</i>), where <i>x</i> is the position along the path). The
goal of this study is to evaluate the performance of scintillometer
<span style="border-top: 1px solid #000; color: #000;"><i>U</i><sub>⊥</sub></span> estimates for conditions under which <i>U</i><sub>⊥</sub> (<i>x</i>) is
variable. Two methods are applied to estimate <span style="border-top: 1px solid #000; color: #000;"><i>U</i><sub>⊥</sub></span> from the
scintillometer signal: the cumulative-spectrum method (relies on
scintillation spectra) and the look-up-table method (relies on time-lagged
correlation functions). The values of <span style="border-top: 1px solid #000; color: #000;"><i>U</i><sub>⊥</sub></span> of both methods
compare well with the lidar estimates, with root-mean-square deviations of
0.71 and 0.73 m s<sup>−1</sup>. This indicates that, given the data treatment
applied in this study, both measurement technologies are able to obtain
estimates of <span style="border-top: 1px solid #000; color: #000;"><i>U</i><sub>⊥</sub></span> in the complex urban environment. The
detailed investigation of four cases indicates that the cumulative-spectrum
method is less susceptible to a variable <i>U</i><sub>⊥</sub> (<i>x</i>) than the look-up-table
method. However, the look-up-table method can be adjusted to improve its
capabilities for estimating <span style="border-top: 1px solid #000; color: #000;"><i>U</i><sub>⊥</sub></span> under conditions under for
which <i>U</i><sub>⊥</sub> (<i>x</i>) is variable. |
|---|---|
| ISSN: | 1867-1381 1867-8548 |