Research On Light Scattering Characteristics And Detection System Of Cloud Particles

In order to deeply understand the radiation transfer characteristics of cold clouds,it is necessary to obtain the information of ice particles in clouds,especially the ice particles whose diameters are less than 50 microns and those particles account for majority of them.Airborne cloud particle observation is an important way to study cloud physics characteristics.In order to construct a polarized cloud particle detector,Basic theory of particle scattering was introduced and T matrix was used to simulate the scattering characteristics of typical aspheric particles,then a polarized cloud particle detection system is designed and constructed.The phase functions of ellipsoids,cylinders and spherical particles,the depolarization ratio at different angles and the total scattering cross section are simulated.It is found that the spherical particles hardly produce depolarization and its depolarization magnitude is several orders less than ellipsoids.Thus spherical particles can be distinguished from particles during detection mission.In addition,the mean values of scattering cross sections and depolarization ratios of aspheric particles in two receiving solid angles of the detector are calculated.The results of particle scattering simulation show that the detection system not only can detect spherical particles,but also can be used to detect aspheric particles.A cloud particle detection system with polarization channel is developed with the optical path designing,mechanical structure designing,signal receiving system designing and signal processing.The detection system uses a 660-nm single-mode fiber-coupled laser as the light source.Through lens combination,the forward(4-14 degrees)and backward(176-146 degrees)scattering light of particles is collected.The receive channel is divided into four channels: forward quality control channel and detection channel,backward parallel polarization channel and vertical polarization channel.A signal receiving and acquisition system was designed to record scattering information of particles for further analysis.Finally,the sensitive region calibration and particle detection experiments were carried out as well as the detection performance of the detector was also analyzed.The experimental data shows that the developed detection system has a certain particle detection ability.