Experiment Research Of Water Vapor Detection With Raman Scattering Of Laser

Water vapor is the gaseous state of water in the atmosphere. Despite its tiny existence,water vapor is the most active constituent in the atmosphere because it is the unique one which has phase transitions. Therefore,water vapor is a crucial factor for weather process,climate change and earth-atmosphere energy exchange.Raman lidar is one of the most efficient tools for atmosphere water vapor detection because of its high temporal and spatial resolution and relatively simple structure. From the late sixties of last century,Many research institutes have made enormous efforts to develop Raman lidar systems for water humidity measurement.The thesis firstly introduces the earth atmosphere and standard atmosphere model,then expounds the interaction mechanism between laser and atmosphere molecule and places great emphasis on Raman scattering principle,spectrum and scattering cross section.The basic principle of Raman lidar for water vapor measurement is introduced in the main part of the thesis. The determination of transmission correction function and system correction constant is analyzed in detail. The hardware,including laser transmitting subsystem,receiving subsystem and data acquisition device is introduced later.The detection capability of lidar system is evaluated by signal to noise ratio and relative uncertainty. From ground to the elevation of 2000m,the relative uncertainty of water vapor measurement is less than 10%. A few typical measurement results are shown and indicate that the Raman lidar have the capability to detection the water vapor mixing ratio from ground to 2000m above sea level with considerable consistency with radiosonde measurement. Nighttime continuous detection demonstrates the ability of the lidar to capture the spatial and temporal evolution of water vapor in the lower troposphere.The experiment validates the reliability of the system ,the accuracy of Raman signal of water vapor and nitrogen and the correctness of the method for the determination of transmission correction function and system correction constant. Key words : Raman Lidar ; Water Vapor Mixing Ratio ; Vertical...