Backward Transmission Detection of Pulsed Laser in Cloud Based on Semi-Analytical Monte Carlo

The distribution of liquid droplets and ice crystals in cloud is completely random, and traditional analytical methods for describing laser propagation in multiple-scattering media could have a significant impact on the estimated results. Therefore, a Monte Carlo simulation method for photon transport process in laser backscattering based on the superimposed scattering theory is proposed. A corresponding photon backward transmission model is established, and the semi-analytical Monte Carlo (SAMC) method is adopted to simulate the laser backscattering signal waveforms and backward scattering ratios at different spatial points of the laser detection system. The results showed that as the concentration of cloud particles increased, the probability of photon reception increased, and the intensity of backward scattering increased. Under representative particle number concentration of stratocumulus, cumulus clouds, and cumulonimbus clouds, the probabilities of photons received by laser echoes were 0.49%, 0.26%, and 0.16%, respectively. The backscattering of clouds is not only related to the particle number concentration, but also to the particle size and absorption under different cloud types. The morphology and particle number concentration of multi-scale cloud particles are important factors affecting laser pulse signal backward scattering, which provides a basis for pulse laser detection system to identify cloud phase information for different cloud types and detect particle concentrations.