On the use cirrus clouds for ground-based elastic lidar calibration

A key parameter to retrieve backscatter coefficient from elastic lidar signals is the backscatter coefficient at a reference height. Traditionally, such a calibration height must fulfil the criterion that at this altitude the particle backscatter coefficient is negligible compared to the molecular backscatter value. Such clean-air conditions are normally given in the upper troposphere. This procedure cannot be applied for those channels that present low signal-to-noise ratio (SNR) at the reference height. To solve this problem an alternative calibration method using cirrus clouds is presented.