Differential Absorption Lidar Measurements of Atmospheric Temperature Profiles: Theory and Experiment

Abstract

The method of measuring atmospheric temperature profiles with differential absorption lidar (DIAL), based on the temperature dependence of oxygen absorption lines in the near infrared, is investigated in some detail. Particularly the influence of Doppler broadening on the Rayleigh-backscattered signal is evaluated, and a correction method for this effect is presented. This correction, however, requires an accurate estimate of the molecular- and particle backscatter contributions, which is hardly achievable by usual lidar inversion techniques. Under realistic conditions, resulting errors may be as high as 10 K. First range-resolved measurements using this technique are presented, using a slightly modified DIAL system originally constructed for water vapor measurements. Temperature profiles in the planetary boundary layer are obtained with a resolution of 82 m vertical and 30 min in time, showing an absolute accuracy of 4 K and an error in the temperature gradient of 0.5 K (100 m)?1. While much better resolution can certainly be achieved by technical improvements, the errors introduced by the uncertainty of the backscatter contributions will remain and determine the accuracy that can be obtained with this method.