Study Of Tropospheric Aerosols Over Wuhan Based On A Raman/Mie Lidar

As China's three decades of reform and opening up, establishing society of harmony, environmental protection is our present goal. Therefore, our living environment is focused on unprecedented attention. Air pollution is one of the most concerned problems. Real-time and quantitative atmospheric aerosol content is an important indicator that determines the degree of air cleaning, but also an important element of weather in the study of climate changes. Developing timely and effective detection means is urgent.Since the invention of laser, the study of atmosphere has beening coming into a new epoch. Lidar can make real-time and long-term observations of aerosol vertical distribution profiles. There are space-based lidar and ground-based lidar, space-based lidar can detect over a wide range of areas, but is easily interfered by the weather such as cloud. So there are often blind observation areas. In Mie Lidar equation, aerosol extinction coefficient and backscattering coefficient are two unknowns. If using Mie Lidar, there must be an assumption about the relationship of them in order to solve the equation. The assumption introduces errors. However, using Raman Lidar principle, aerosol extinction coefficient can be inversed accurately without making this assumption. This paper developed a ground-based Raman/Mie multi-channel lidar system, real-time and accurate vertical distribution of aerosol optical properties in the low troposphere over Wuhan will be detected.At first, the previous work is concluded and the status quo of atmospheric aerosol research and development prospects is studied. A ground-based Raman/Mie multi-channel lidar system is designed in accordance with the status quo of atmospheric aerosol over Wuhan. All system parameters are estimated and the lidar's operating characteristics are simulated. Then the entire including hardware and software are integrated and signal tests are done to make sure that signals in all channels are received well. Second, the methods of inversing atmospheric aerosol extinction coefficient, backscattering coefficient and lidar ratio are studied and the simulation experiments are done to verify the correctness and feasibility of the inversion method. Third, based on the self-developed Raman/Mie multi-channel lidar system, real-time vertical distribution profiles of atmospheric aerosol extinction coefficient, backscattering coefficient and the lidar ratio are detected. And long-term observations are done to get a view of atmospheric aerosols' distribution and variation in Wuhan area. Fourth, research the atmospheric boundary layer and detect the height of it over Wuhan by the lidar system. Finally, temperature inversion in the night is surveyed based on lidar.In the course of the study, some key technical issues have been solved and some method has been improved. As the Raman scattering signal is very weak and background noise must be suppressed effectively in order to ensure the Raman scattering signal will not be submerged. We use the military detection technology to measure the surrounding electromagnetic noise and then enter it into the software for subtraction; Aerosol extinction coefficient can be retrieved accurately by the Raman lidar signals. Combined with Mie scattering signals in the same field of view, aerosol backscattering coefficient can be obtained. The key point here is to ensure that Mie-channel signal and the Raman-channel signal must come from the same field of view. Lidar ratios retrieved by Raman backscatter signals, work as the input conditions for Mie lidar equation to get aerosol extinction coefficients and backscatter coefficients. Then compare the results of two methods. If they are in good agreement with each other, the two-channels are from the same field of view. Detecting the height of atmospheric boundary layer is also a greatest concern. Different researchers can give different criterion and different results. There are a lot of direct observation techniques, such as meteorological tower observations, tethered balloon, and the release of balloons, remote control and fly jet fighters as well as some remote sensing technology. But the most direct and effective means is the lidar because it can make real-time and continuous observation. In this paper, the height of atmospheric boundary layer and its changes during the night are measured based on the Raman lidar. And the method of SBH99 in the Mie lidar analyses is improved. At the same time the detection of height of temperature inversion is also carried out.