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Accuracy of Wind Measurements Using an Airborne Doppler Lidar

John J. CarrollDepartment of Land, Air and Water Resources, University of California, Davis, CA 95616

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Abstract

Errors in airborne Doppler lidar measurements of the wind are evaluated using simulated wind fields and simulated lidar data derived from these wind fields. The primary motivation for this study is the evaluation of several sources of error in the measurement technique. Two types of errors are examined: those due to errors in aircraft velocity and those due to the displacement of the spatially varying wind field during the time between two intersecting looks at the sample volume.

It is found that small errors in the measured aircraft ground speed and track angle produce large errors in the recovered wind speed and direction. Errors in recovered wind speed and direction are strongly dependent on wind direction relative to the flight path. Errors due to nonsimultancous samples can also be large, and are strong functions of the range to the sample volume, wind direction, wind speed, and disturbance amplitude. Recovery of accurate wind fields in such cases requires that the lidar data be displaced to account for advection so that the intersections are defined by air parcels rather than fixed points in space.

The analysis is focused on a particular type of lidar system, but in fact, the results are applicable to other remote sensing systems, such as Doppler radars, that do not utilize simultaneous sampling of the same sample volume.

Abstract

Errors in airborne Doppler lidar measurements of the wind are evaluated using simulated wind fields and simulated lidar data derived from these wind fields. The primary motivation for this study is the evaluation of several sources of error in the measurement technique. Two types of errors are examined: those due to errors in aircraft velocity and those due to the displacement of the spatially varying wind field during the time between two intersecting looks at the sample volume.

It is found that small errors in the measured aircraft ground speed and track angle produce large errors in the recovered wind speed and direction. Errors in recovered wind speed and direction are strongly dependent on wind direction relative to the flight path. Errors due to nonsimultancous samples can also be large, and are strong functions of the range to the sample volume, wind direction, wind speed, and disturbance amplitude. Recovery of accurate wind fields in such cases requires that the lidar data be displaced to account for advection so that the intersections are defined by air parcels rather than fixed points in space.

The analysis is focused on a particular type of lidar system, but in fact, the results are applicable to other remote sensing systems, such as Doppler radars, that do not utilize simultaneous sampling of the same sample volume.

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