Raman lidar measurements of aerosol and water vapour distribution in the atmosphere: A novel method of signal processing

摘要

Raman lidar is one of the active remote sensors of atmospheric water vapour. This method also provides reliable information on microphysical parameters of aerosol particles in the atmosphere. Raman lidar uses elastic and inelastic backscatter to derive the profiles of key atmospheric parameters. The prime advantage of this method is the direct determination of particle backscatter and extinction coefficients along with atmospheric water vapor simultaneously. The optical part of lidar system employs a set of wavelength separating mirrors and high-spectral-resolution interference filters to separate the vibrational Raman signals from the strong elastic backscattering signal. Since Raman signal strengths are weak in nature than compared to the elastic, the detected signals need to be recorded using a unique data acquisition system. The special data acquisition system uses both analog and photon counting electronics, which allows enhanced dynamic range in the measured signals. In order to achieve the enhancement in measured profiles, a gluing technique is required to apply between the signals of analog and photon counting. This paper presents an efficient gluing algorithm to retrieve the profiles of elastic and Raman signals from the functional Raman lidar.