Chirp-Induced Bias in Velocity Measurements by a Coherent Doppler CO2 Lidar

Alain M. Dabas Météo-France, Centre National de Recherches Météorologiques, Toulouse, France

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Philippe Drobinski Centre National de la Recherche Scientifique, Laboratoire de Métérologie Dynamique, Ecole Polytechnique, Palaiseau, France

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Pierre H. Flamant Centre National de la Recherche Scientifique, Laboratoire de Métérologie Dynamique, Ecole Polytechnique, Palaiseau, France

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Abstract

Radial wind velocity measurements by a pulsed CO2 Doppler lidar may be biased even in stationary atmospheric conditions. The authors show it is due to random speckle fluctuations of the backscattered signal and is related to the dissymmetry of the transmitted laser pulse periodogram. A procedure is proposed to correct for the bias on a shot-to-shot basis when a pulse-pair mean-frequency estimator is used for processing. The procedure is validated on simulated and actual lidar signals.

Corresponding author address: Dr. Alain M. Dabas, CNRM/GMEI, 42 Av. Coriolis, 31057 Toulouse, Cedex 1, France.

Abstract

Radial wind velocity measurements by a pulsed CO2 Doppler lidar may be biased even in stationary atmospheric conditions. The authors show it is due to random speckle fluctuations of the backscattered signal and is related to the dissymmetry of the transmitted laser pulse periodogram. A procedure is proposed to correct for the bias on a shot-to-shot basis when a pulse-pair mean-frequency estimator is used for processing. The procedure is validated on simulated and actual lidar signals.

Corresponding author address: Dr. Alain M. Dabas, CNRM/GMEI, 42 Av. Coriolis, 31057 Toulouse, Cedex 1, France.

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