Remote Measurements of Boundary-Layer Wind Profiles Using a CW Doppler Lidar

F. Köpp Institute for Optoelectronics, DFVLR Oberpfaffenhofen, D-8031 Wessling/Obb., Federal Republic of Germany

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R. L. Schwiesow Institute for Optoelectronics, DFVLR Oberpfaffenhofen, D-8031 Wessling/Obb., Federal Republic of Germany

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Ch Werner Institute for Optoelectronics, DFVLR Oberpfaffenhofen, D-8031 Wessling/Obb., Federal Republic of Germany

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Abstract

We have demonstrated practical measurement of profiles of horizontal wind magnitude and direction to altitudes of 750 m by making radial velocity measurements with a Doppler lidar using conical scanning. Comparison with surface anemometers and with profiles measured by balloon sondes allows one to evaluate the consistency between lidar measurements and more conventional sensors. Overall we find a correlation coefficient of 0.83 and an rms difference of 1.3 m s−1 for magnitude and a correlation coefficient of 0.91 and an rms difference of 12° for direction when the lidar and sonde profiles are compared. The differences are not a result of lidar errors because comparisons of 20 s averages between the lidar and a sonic anemometer show a correlation coefficient of 0.98, an rms difference of 0.19 m s−1, and a long-term average difference of 0.05 m s−1 for a single component. Profile differences are attributable to horizontal inhomogeneity in the wind field and uncertainty inherent in balloon sondes. Impaired visibility reduces the effective range of the lidar, and the vertical extent of the lidar sample region increases with height.s

Abstract

We have demonstrated practical measurement of profiles of horizontal wind magnitude and direction to altitudes of 750 m by making radial velocity measurements with a Doppler lidar using conical scanning. Comparison with surface anemometers and with profiles measured by balloon sondes allows one to evaluate the consistency between lidar measurements and more conventional sensors. Overall we find a correlation coefficient of 0.83 and an rms difference of 1.3 m s−1 for magnitude and a correlation coefficient of 0.91 and an rms difference of 12° for direction when the lidar and sonde profiles are compared. The differences are not a result of lidar errors because comparisons of 20 s averages between the lidar and a sonic anemometer show a correlation coefficient of 0.98, an rms difference of 0.19 m s−1, and a long-term average difference of 0.05 m s−1 for a single component. Profile differences are attributable to horizontal inhomogeneity in the wind field and uncertainty inherent in balloon sondes. Impaired visibility reduces the effective range of the lidar, and the vertical extent of the lidar sample region increases with height.s

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